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10th International Conference on Maintenance and Rehabilitation of Pavements
Abstract: A robust pavement infrastructure is essential for safeguarding the environment, economy, and society. Autonomous and connected vehicles, including trucks, offer the potential to decrease energy consumption, emissions, and costs, while simultaneously enhancing road safety. Therefore, the future vision for pavements must be comprehensive: ensuring safety, achieving net-zero emissions, maximizing efficiency, and demonstrating durability, all while minimizing disruption to travelers and freight. Future traffic patterns, particularly the introduction of truck platoons and electric freight, present challenges to the performance of flexible pavement. This necessitates the exploration of optimization techniques to transform these challenges into opportunities, which will be discussed in the presentation.
Abstract. University of Iowa, jointly with Iowa State University, has performed a research project of over $1 million to develop quality standards for inclusion of high recycled asphalt pavement (RAP) content in asphalt mixtures for Iowa Highway Research Board and Iowa DOT. This keynote presentation will discuss various aspects of asphalt pavement recycling which include RAP fractionations, effects of rejuvenators, both laboratory and field tests and a comprehensive evaluation of asphalt pavement recycling strategies which include Plant and In-place Recycling of Hot, Warm, Cool and Cold asphalt mixtures.
Abstract: Moisture susceptibility has been recognized as a major pavement distress. This study examines the resistance to moisture damage of lime-modified asphalt mixtures containing EAF slag. For this study, seventeen (17) mixtures containing 0-4% of lime and 0-100% of slag was generated using Box Behnken Design (BBD) in design expert. The asphalt mixture samples were prepared and the moisture susceptibility was determined based on the immersion compression test (Index of retained strength). The experimental results obtained indicate that lime as additive helps reduce moisture damage of steel slag asphalt mixtures in several mechanical and chemical ways. The ANOVA indicate that the lime content is the most in-fluencing and significant factor after showing the highest F-values of 10.93 and 6.73 for retained strength index at curing days of 1 and 21-day, respec-tively. The response surface shows that the Steel slag and lime have signifi-cant interactive effects on the RSI. Furthermore, the optimization result shows that 1.376% of lime, 100% steel-slag and 4.435% bitumen content are the ideal values to meet the design requirements.
Abstract: Since the late 1980s, government agencies have used porous asphalt-treated courses (PATC) as drainage layers under Portland cement concrete and asphalt concrete to prevent premature pavement failure by allowing water to drain from the pavement structure. Although PATC has been used in other applications, its use in airports is relatively limited. Three different types of PATC mixes were evaluated for use as a permeable base layers for runways and taxiways: #57, #67, and porous asphalt concrete. A constant-head permeability test was developed in this study to measure the permeability coefficient of PATC mixes because traditional methods are inadequate to highly permeable materials. A linear relationship was found between total air voids and connected air voids for PATC specimens. The regression line approached the equality line as air content increased, with a slope greater than 1. Test results illustrate that as specimens become more porous, the air voids tend to become interconnected, and more voids are likely to be filled with water. To meet the permeability specification, the total air void content for PATC mixes should be controlled between 17% and 24%. Additionally, the addition of fine aggregate to the #57 and #67 mixes needs to be controlled between 17% and 34% to provide stability and proper permeability.
Abstract: Self-healing by induction heating stands as a promising and sus-tainable technology for asphalt pavement maintenance applications. This study involves performing a series of test cycles, encompassing first SCB fracture testing on a waste steel fiber (WSF)-reinforced for an asphalt con-crete for thin surface layers (BBTM) and asphalt concrete for binder layer (ACL), induction heating for healing, and subsequent second SCB fracture testing. The research aims to analyze how crack healing ability changes with a semi-circular bending (SCB) test before and after healing, considering the combination of BBTM and ACL with different WSF content. Based on the SCB test fractural parameters, the healing indexes (HI) are obtained through peak load (Fmax) and critical stress intensity factor (KIC). Additionally, the fracture parameter results obtained based on the amount of WSF in the BBTMs and ACLs are consistent with the results of the indirect tension to cylindrical specimen (IT-CY) test. Consequently, it was emphasized that asphalt mixtures containing WSF have the potential to heal cracks through induction heating, and the healing ability can be improved depending on the WSF content of the wearing and binder layer. In addition, it was shown that ACL and BBTM samples with higher stiffness values are much more difficult to heal in terms of Fmax and KIC.
Abstract: In Australia, thin (50-80 mm) asphalt is widely used as the primary type of surfacing for airfield pavements. The function of the asphalt surface is to provide a flexible, waterproof, durable, and skid-resistant wearing layer on top of the pavement structure. During production of airfield asphalt, variable constituents result in variations in the air void content of the mixture. Monte Carlo simulation was used to generate datasets, based on actual airfield asphalt production data, to determine the variance of air voids, and the effect that the different production variances had on the resulting air void content. It was found that the coarse aggregate (gravel) fraction gradings had the greatest influence on the air voids in the mixture, followed by the fine aggregate gradations and the bituminous binder content. It is recommended that the tolerances for production (Marshall) air voids in the current Australian airport asphalt specification be revised from a tolerance that is tied to the mixture design, to a fixed range. This will also allow the specification to be tightened, to a range that is still practically achievable, and that has been recommended previously.
Abstract: Grouted macadam (GM), composed by a porous asphalt mixture whose air voids are filled with a cementitious grout, is efficiently used as wearing course in semi-flexible pavements subjected to heavy-load traffic and low speed. Since high steering angles, applied by vehicle load at low speed, induce high shear stresses on the surface, this research investigated the raveling resistance of GM in comparison with conventional asphalt mixtures usually employed in motorways and airports. Laboratory tests were carried out with the Darmstadt Scuffing Device, which simulates the actual in-field movement of a wheel during steering. Several environmental factors were simulated, varying the testing temperature and the conditioning of the specimens. Experimental results showed that GM ensures a satisfactory raveling resistance in the conditions of dry and wet surface, comparable with those of asphalt concretes. On the contrary, an outstanding behavior was registered for GM in the case of fuel spillage, thanks to its close structure which does not allow penetration and to the grout which guarantees chemical resistance.
Abstract: In recent years, the excellent mechanical properties of asphalt modified with graphene nano-platelets (GNPs) have attracted a growing number of researchers investigating their actual performance enhancement in pavements. First, the authors analyzed an original thin layer of graphene-modified asphalt (GMTL) aimed at restoring the binder layer of road pave-ment through laboratory and trial section tests. The laboratory results demonstrate improvements in indirect tensile resistance, an increase in the modulus of elasticity of the binder, and a reduction in material deformation, consistent with findings from other international investigations. However, there is a lack of known studies on test sections or specific research involv-ing thin layers with added GNPs. This paper particularly focuses on as-sessing, through FWD equipment, the reduction in deflection and the in-crease in modulus within a real pavement. The investigated GMTL (1.0 cm thick) exhibits an average reduction of 9.5% in maximum FWD deflections and 14.9% in HMA deformability. Moreover, the back-calculation indicates improved stiffness modulus of the pavement foundation (+37%) and the cement-treated base layer (+68%) in pavements covered with GMTL. Fur-ther, comparative studies regarding strength, thermal susceptibility, and service life will be necessary to enhance our understanding of GMTL.
Abstract. After the success of the electric cars, the future will be based on Connected and Autonomous Vehicles (CAVs) that will change the actual driving mode. CAVs will also change the design of road pavements because their transverse position in the lane produces different distresses compared to the actual cars due to CAVs ability to keep their transverse position con-stantly in the lane, eliminating lateral wandering and inducing more damage to pavements than conventional vehicles. It is crucial to evaluate how the wander of CAVs affects pavement performance for the definition of mainte-nance and rehabilitation policies. This paper analyses how the lateral wan-der of CAVs affects pavement performance in terms of fatigue cracking and permanent deformation. These results can be used to establish the values for the wander to minimize those distresses in road pavements. This work was carried out for a pavement with three layers, changing the thickness of the asphalt layer and the stiffness of the subgrade. The wander varied from 0.2 to 0.6 m, applying a normal and a uniform distribution. The variation of the pavement life due to the wander was modeled using Artificial Neural Net-works (ANN) and models were developed for these two distributions and for cracking and permanent deformation distresses. It was concluded that a significant damage reduction occurred as the wander increased, and the probability distribution also shaped the damage profiles. The developed ANN models showed that they are suitable tools for predicting the perfor-mance of pavement subject to any wheel wander.
Abstract. The low volume rural road pavement is designed with unbound granular layers only which may be designed against rutting. The objective of present paper is to estimate the thickness of granular base layer of pavement based on mechanistic-empirical approach. In present analysis, the pavement has been considered as multi-layered system. Odemark’s method has been used to transform the multi layered system into an equivalent single layer homogenous medium. In order to estimate the vertical interface stress and strain on the top of natural subgrade, Boussenesq’s theory has been used. For estimation of granular base and sub base thickness, the allowable stress and strain on subgrade have been considered from Huang’s corelation and recommendations from IRC:37-2018 .The pavement thickness thus obtained using present stress and strain based approach have been compared with thickness obtained using AASTHO guideline and IRC:SP:72-2015, the guidelines based on loss in serviceability of road pavement. However, comparison of results show good agreement in higher subgrade CBR range in stress based present approach whereas the strain based approach shows better convergence with lower range of subgrade CBR. In this backdrop, proposed method may be considered as an acceptable and reliable approach for estimation pavement thickness for low volume granular road pavement.
Abstract. Hot-Mix Asphalt (HMA) creep compliance is a primary mechani-cal property input for the AASHTOWare Pavement Mechanistic-Empirical Design (PMED) software for design analysis of rehabilitated pavements. This study investigated the impact of the creep of HMA mixes with re-claimed asphalt pavement (RAP) on the performance of the HMA-overlaid pavements in Kansas. Hierarchical Level 1 inputs of creep compliance were obtained for two overlay mixtures by the AASHTO T 322-07 test method. Level 3 inputs were obtained as defaults in the PMED analysis software. Twenty-five asphalt concrete (AC) overlays over existing AC and 14 AC overlays over Jointed Plain Concrete Pavement (JPCP) were selected to make distress predictions using the AASHTOWare PMED software (ver-sion 6.2). The failure criteria for new asphalt pavements were used in PMED. The distresses predicted include roughness (in terms of the Interna-tional Roughness Index, IRI), permanent deformation (rutting), AC total transverse cracking (thermal plus reflective), AC thermal cracking, AC fa-tigue cracking (both bottom-up and top-down), and JCPC transverse crack-ing in terms of percent slabs (AC overlay over JPCP only). The results show that mixtures with softer binders produced less thermal cracking for AC overlays on existing AC pavements. For AC overlays on existing JPCP, a mixture with a lower PG-grade binder eliminated thermal cracking on the AC overlays. For most projects, a softer binder also helped decrease the to-tal transverse cracking.
Abstract. Dynamic modulus of Hot-Mix Asphalt (HMA) is a primary mechanical property input for flexible pavement design analysis using the AASHTOWare Pavement Mechanistic-Empirical Design (PMED) software. In this research, dynamic modulus inputs were used for design analysis of 21 newly constructed asphalt surface projects with the PMED software to predict asphalt pavement performance and to compare hierarchical Level 1 and Level 3 inputs. Level 1 inputs were obtained from the dynamic modulus tests conducted on mixtures up to 25% recycled asphalt content (RAP) following the AASHTO T 342-22 standard test methods. Level 3 inputs were obtained as defaults in the PMED analysis software. The PMED software predicted two load-related cracks associated with dynamic modulus: asphalt concrete (AC) longitudinal cracking (top-down cracking) and alligator cracking (bottom-up cracking). Roughness in terms of the International Roughness Index (IRI), permanent deformation (rutting), and thermal cracking were also predicted. The results show that for minor arterial projects, in most cases, the projects failed in AC bottom-up fatigue cracking for both Level 1 and 3 input levels. Comparing Level 1 to Level 3 distress prediction, the AC top-down fatigue cracking drastically increased but did not exceed the target value. The other predicted distresses were similar for Level 1 and 3 inputs. These observations regarding top-down cracking and other distress were also observed for the principal arterial projects. With reduced AC thickness, bottom-up fatigue cracking and terminal IRI increased for all minor and principal arterial projects. Other distresses remained the same irrespective of project type or levels of HMA dynamic modulus inputs.
Abstract. The PMED performance models have been nationally calibrated and may not represent local conditions in a region. Therefore, these models should be calibrated considering the local construction practices, performance, and climatic conditions. An essential step in the calibration process is to select pavement sections. This paper presents a systematic approach to obtaining observed performance and selecting sections for local calibration of flexible and rigid pavement models. The authors analyzed the distress data retrieved from MDOT's PMS and sensor database and successfully converted it into units compatible with the PMED. The converted data was checked to filter for anomalies and cut-off limits, ensuring the practicality of measured performance. The paper also defines specific criteria for project selection that include the need for a minimum number of data points, positive distress trends, and maintenance history. After selection, each section was categorized into good, fair, and poor-performing pavements and compared against all MDOT sections. This was to ensure that the selected sections represent overall data. The paper documents a stepwise approach to consider observed performance and select representative pavement section samples for optimal local calibration.
Abstract. Micromechanical modelling through the Discrete Element Meth-od (DEM) is adopted for the study of bituminous materials given its capa-bility to replicate complex microstructures behaviour. Typically, DEM models of bituminous materials consist of an assembly of randomly dis-tributed spherical rigid particles which interact using elastic and/or simple viscoelastic contact models, and individual aggregates are represented by single particles. However, recent years have witnessed a notable surge in re-search efforts aimed at incorporating true particle morphologies into numer-ical models. In the context of this research, an existing 3D DEM model for bituminous materials has been refined with the representation of mineral aggregates with realistic particle shapes. To achieve this, a digital library of aggregate shapes was constructed from X-ray computed tomography (CT) scans. An adaptive image-processing technique was employed to isolate the aggregates in the CT images, and the Delaunay method was used to create a 3D surface model of the aggregates. Several virtual aggregates with varying sizes were selected from this library to mirror the gradation of coarse aggre-gates in the 3D DEM asphalt model. Each virtual aggregate was discretized using smaller spherical particles, with its deformability given by its inner particle contacts. To evaluate the effectiveness of this enhanced approach, numerical assemblies featuring realistic particle shapes were subjected to a cyclic loading protocol. Overall, realistic particles shapes increased the stiffness modulus and decreased the phase angle of numerical specimens, and the effect was greater with a finer discretization of aggregates. The out-comes clearly demonstrate the importance of this numerical improvement to accurately simulate the bituminous mixture behaviour.
Abstract. Skid resistance is a critical factor for road safety, particularly in adverse weather conditions, as it directly impacts a vehicle's braking and maneuvering abilities. Grooved pavements have been employed to enhance skid resistance on highways and airport runways. However, over time, wear and tear can reduce their effectiveness. Therefore, continuous monitoring of the skid resistance performance of grooved road surfaces is essential. Unfortunately, there is currently no specific standard method for testing the skid resistance performance of grooved road surfaces. In this study, different groove patterns and specimen types were initially evaluated using the British Pendulum Tester (BPT). Subsequently, BPT simulation models and skid resistance simulation models were employed to calculate the actual skid resistance performance of grooved road surfaces. The results indicate that when BPT testing angles exceed 40°, the BPT test results tend to overestimate the road surface's skid resistance. This paper introduces a correction procedure to adjust the BPN values of grooved road surfaces, providing a robust theoretical framework for the practical implementation of BPT in monitoring the deterioration in skid resistance performance of grooved pavement surfaces.
Abstract. Transportation agencies need performance indicators to report the pavement condition. Many local transportation agencies use the Pavement Condition Index (PCI) to report the pavement condition. In 1986, the World Bank developed the International Roughness Index (IRI) to measure the irregularity of the road surface. IRI is an indicator of roughness for straight horizontal road segments simulating a quarter-car travelling at 50 mi/h. In the United States, the Federal Highway Administration (FHWA) has established criteria to report a pavement in good, fair, or poor condition. IRI, percentage of cracking, and rutting thresholds are established by the FHWA to assess the pavement condition. Local roads represent, in terms of mileage, the largest percentage of all roads in the U.S. IRI is not typically measured on local roads due to speed restrictions, short section lengths, traffic signals, traffic congestion, intersection treatments, and geometry characteristics. PCI and IRI represent different concepts and measure different aspects of pavement performance. Despite these differences, there is a need to report the pavement condition of local roads in a consistent manner. PCI and IRI datasets from a total of 25,229 asphalt surfaced pavement sections were analyzed using statistical descriptive analysis and expert knowledge to develop transfer equations. The product of this hybrid modeling approach is a best-fit sigmoidal equation presented in this paper to estimate the IRI value from the PCI value, and recommended threshold equivalent values to report the pavement condition.
Abstract. Grip, or skid-resistance, is a fundamental attribute of a racetrack and needs to be understood by track owners, operators and racing teams. An analysis of racetrack wet grip produced datasets comprising tens of thousands of geolocated data points. The aim of this paper is to demonstrate that the datasets can be used to create Triangular Irregular Networks (TINs) that present grip morphology as digital surfaces. Wet grip data was collected from three racetracks using a Findlay Irvine GripTester. The recorded friction coefficients are known as Grip Numbers (GNs). The data sets were aggregated and plotted in CAD software OpenRoads Designer (ORD) and used to create a grip Triangular Irregular Network (TIN) for each track. Linear interpolation was applied to the data points to produce a continuous wet grip surface. The wet grip surfaces are presented as thematic maps and a data structure that could be used for further surface analysis. This results in a novel development that advances the display of grip variation beyond mapping discrete point data to interpolating GripNumbers between point data collected at the track.
Abstract. The paper presents a system aiming at characterizing water spray induced by a tire rolling on a wet road and relating it to the water depth on the road surface. Water splash and spray mechanisms are briefly reminded and definition of water depths are given. The system setup, composed of ac-celerometers to record vibrations of the front wheel arch liner, is described. Tests are performed with a passenger car on various road surfaces and at dif-ferent vehicle speeds and water depths. Signals recorded by the accelerome-ters are filtered and processed. The link between the acceleration amplitude, the water depth, and the vehicle speed is consistent with results from pre-vious studies. A mathematical model is proposed to relate the acceleration amplitude to the water depth. The effect of the surface macrotexture, based on the Mean Texture Depth, is less obvious. Suggestions are made for fur-ther investigations based on 3D topographical maps and texture indicators related to water drainage mechanisms.
Abstract. Transportation Safety continues to evolve as a significant area of interest and concern. As a result, evaluation of safety from a pavement surface characteristics perspective is also attracting additional interest. Historically, pavement safety assessments have focused on discrete, low density friction assessments with common technology not changing much in the past half century - this notwithstanding significant changes/improvements in automotive braking systems and exploration of alternative methodologies for pavement surface assessment. Not surprisingly, current methodologies continue to involve test tyres assessing frictional resistance. Interest has always existed in exploring the relationship between texture and friction, in part, because texture can be assessed with non-contact technologies. Unfortunately, neither friction nor texture were previously collected with sufficient density and precision to establish any meaningful correlation. With the availability of more comprehensive integrated pavement surface assessments, more detailed investigations and analysis are now feasible.
Abstract. Sealing or filling cracks in pavement surfaces has been a common pavement maintenance technique adopted by many agencies. Mastic has been a common material implemented in these activities due to its flexibility, adhesion, and strength properties. In cold regions, the presence of freeze and thaw cycles contributes to the generation of severe transverse cracks that impact ride quality. Therefore, the main objective of this study is to evaluate the effect of transverse mastic sealant on pavement roughness as an indicator of ride quality on multiple pavement surfaces. Field performance data from a cold climate and low-traffic roadway was obtained before and after mastic application and analyzed using hierarchical cluster analysis. The main results suggest that this repair strategy can be effective in improving the roughness of pavements in cold regions. Nevertheless, the magnitude of the given benefit is dependent on the pre-existing roughness condition and surface type.
Abstract. The present study has been developed to investigate the combined effect of 20 % de-icing salts solutions (calcium chloride, magnesium chloride and sodium chloride) and freeze and thaw (F–T) cycles on bituminous binders and asphalt mixture performance at medium and low service temperatures. In the study were included conventional and SBS-polymer modified bitumen with amido-amines based anti-stripping additive. Twenty F-T cycles were carried out (16 h at (18 ± 2) oC and 8 h at (20 ±2) oC). Bituminous binders and asphalt mixtures were subjected to short and long term aging. Unaged and aged binders and asphalt mixtures were subjected to the combined impact of salts solutions and F-T cycles. For bituminous binders fatigue parameter (G*.sin(δ)), flexural creep stiffness S and “m-value” were determined and for compacted asphalt mixtures indirect tensile strength ratio at 0oC was determined. The main conclusions from the study are as follow: SBS-polymer modified bitumen show better low temperature and fatigue resistance than conventional bitumen; De-icing salts solutions combined with freeze and thaw cycles have negative impact on both asphalt mixtures and bituminous binders’ performance at medium and low temperatures.
Abstract. The mechanism of moisture damage at the bitumen-aggregate in-terface is a crucial but unresolved issue in pavement engineering. In this pa-per, an innovative molecular dynamics (MD) modeling approach was de-veloped to address this challenge. This method incorporates nanoscale moisture diffusion and migration into consideration, which provides a more accurate representation of the real damage process. Bitumen and two minerals, namely quartz and calcite, are selected to construct the simulation model. The model is subjected to pore water pressure to simulate the bitu-men-aggregate interfacial debonding process. Simulation results reveal a non-uniform diffusion phenomenon at the interface: the closer water mole-cules are to the aggregate surface, the weaker their ability to diffuse and mi-grate, which significantly affects the interfacial debonding process. Find-ings from this research contribute to comprehending the fundamental debonding mechanisms and provide an atomic-level perspective to investi-gate the moisture damage in pavement engineering.
Abstract. In this experimental laboratory study, a 0-10mm bituminous surface mix (ESG-10) was developed with a softer and unmodified bi-tumen PG58S‒28 for standard traffics and cold regions and, with 0, 5 and 20% softwood Kraft lignin that was added by the dry process i.e., directly in the hot mix asphalt (HMA). The study encompassed the evaluation of compactability, moisture sensitivity, rutting resistance, and thermal cracking resistance. The mix design resulted in a single gra-dation, maintaining a constant binder (bitumen and lignin) content of 5.29% by the total weight for all mix variations. In particular, lignin was considered a binder in its own right, and the results revealed shifts in properties related to binder density, compaction ability, and moisture resistance of HMA, suggesting that the addition of lignin impacts the mix characteristics, especially at higher lignin concentrations. The study also explored rutting resistance and thermal cracking resistance, with re-sults indicating some interactions between lignin, bitumen, and mix properties. Overall, this research provides valuable insights into the in-tricate relationship between lignin and bitumen in bituminous mixes, offering information about their suitability and effects on the perfor-mance of asphalt.
Abstract. The output of the gyratory compactor is frequently used to design and study the asphalt mixture properties, such as compacity and workabil-ity. To exploit some characteristics of these curves the use of fitting models is recommended. The sigmoidal model is one of the fitting models with more potential due to the possibility of identifying several particularities of the compacity-gyrations curve, such as, its inflection point and maxi-mum slope, or even the slope for any given number of gyrations. However, the precision, i.e., repeatability and reproducibility, of the model parameters is still unknown. This round-robin on gyratory compaction, involving 22 participants, is a contribution to fill that gap-in-knowledge. The experi-mental compaction data was used to determine the sigmoidal model parame-ters and the respective precision values were determined following ISO 5725-2:2019. In addition, the log-linear model from EN 12697-10:2017 was also used, and the obtained precision values were compared with literature. For both models, to quantify the effect of the number of gy-rations used to determine the parameters of the models, three cases were considered: 60, 120, and 200 gyrations. It was found that the use of a higher number of gyrations improved the precision values and allowed for a better estimation of the parameters. Regarding the ability of the models to fit the experimental data, the sigmoidal model showed a lower RMSE, approxi-mately six times lower than the log-linear model.
Abstract. Interface shear strength of road pavements plays a crucial role on overall structural performance. Interface between asphalt layers is common-ly treated by applying a bituminous tack coat emulsion. Specific pavement structures such as the Asphalt Solar Collectors (ASCs) can be constructed installing pipes or coils at the above-mentioned interfaces. Given this background, the present research was based on a Finite Element Analysis (FEA) and a related experimental activity to verify the suitability of includ-ing an ASC in the upper interface of a flexible pavement, 4 cm under the rolling surface. Shear strength FEA simulated an emergency heavy-truck braking to maximize stresses transmitted at the interface. Comparing the shear resistance at the interface with the FEA-simulated tangential stresses, it was found that the installation of the coils 4 cm under the road surface could threaten the structural integrity of the pavement. Thus, a 5 cm thick-ness for the overlay asphalt layer was suggested to avert possible design is-sues.
Abstract. The integration of healing capsules into asphalt mixtures has demonstrated promising advancements in their intrinsic self-healing prop-erties. However, the efficacy of this technology still requires further inves-tigation. Rigid particle models, utilizing the discrete element method (DEM), have been adopted to simulate the creep, fracture, and viscoelastic behavior of asphalt mixtures, accounting for their irregular microstructure and particle contacts. This study utilizes the previously developed Virtu-alPM3DLab, a three-dimensional DEM framework, to numerically assess the impact of rejuvenator-modified mastic particles on the stiffness proper-ties of post-healed asphalt mixtures where the asphalt mixture has under-gone healing. Simulations consider different capsule proportions (0.30, 0.75, and 1.20 wt%) incorporated in the specimens. Numerical results re-veal that the encapsulated rejuvenator reduces the stiffness modulus of as-phalt mixtures, with this impact becoming more pronounced as the capsule amount increases due to the additional rejuvenator representation in the specimen. In addition, the phase angle remains unaffected across all numeri-cal scenarios, suggesting that the viscoelastic behavior of asphalt mixtures is not significantly impacted and indicating the suitability of capsules for pavement applications. The findings also suggest that the percentage of these healing elements can slightly surpass the traditional amounts com-monly used in laboratory settings.
Abstract. The AASHTOWare mechanistic-empirical pavement design (PMED) is a state-of-the-art new and rehabilitation project design proce-dure that accounts for local environmental conditions, highway materials, and actual highway traffic distribution using axle load spectra. The distress prediction models must be calibrated for a particular state or region to apply this procedure precisely. However, generating input data for calibration is one of the most challenging aspects of the calibration process. This paper describes the input data collection process for PMED calibration for reha-bilitated pavements in Kansas, a midwestern state in the United States.
Abstract. This paper presents a study of the applicability of the MeDiNa pavement design methodology, a mechanistic-empirical software developed in Brazil, to the Portuguese pavement structures. The paper describes the main features and assumptions of the MeDiNa software, and compares the predicted pavement performance indicators, such as cracking and rutting, with the Portuguese specifications and pavement design practice. The paper also discusses the data requirements and challenges for using the MeDiNa software in a different country, and suggests some future developments, such as local calibration, integration with pavement management systems, and prediction of the International Roughness Index. The paper concludes that the MeDiNa software could be a useful tool for road agencies in Portugal, but it would need comprehensive and wide data collection and adaptation to the Portuguese context.
Abstract: The paper is devoted to high modulus asphalt concrete, more commonly known as EME or HMAC. The general characteristics of the mixture were presented, with particular emphasis on fatigue life and the impact on the design life of the pavement structure, based on experience from various countries. Computational analyses of typical structures were carried out using the mechanistic method, the impact of the use of EME type mixtures was demonstrated, also indicating the potential for use in long-life pavements, and typical solutions adapted to the traffic category were proposed. Calculations were carried out using the deterministic and probabilistic methods using the NOAH software.
Abstract. The maintenance and rehabilitation of flexible pavements gener-ates an appreciable volume of waste from the reclaimed asphalt pavement (RAP). One of the processes for the RAP valorization is the transformation into recycled aggregates to be reintegrated in the pavement life cycle, to-wards a circular economy model. Unbound granular layers of flexible pave-ments are a field of application of these recycled aggregates. The objective of the paper is to present a catalogue of flexible pavements incorporating RAP in unbound granular layers, developed in Portugal for low volume roads. Beyond the catalogue, the paper describes the research work developed to demonstrate the mechanical and environmental performances of the pro-posed pavement structures. In laboratory, cyclic triaxial tests and leaching tests were conducted in addition to current geometric, physical, and me-chanical tests. Load tests were carried out on experimental full-scale pave-ments to validate the mechanical behavior of RAP mixtures in real condi-tions of application. The paper introduces traffic, materials, and subgrade conditions that supported the application of the catalogue. The catalogue aims to contribute for the implementation of sustainable pavement solu-tions in road construction.
Abstract. There is significant attention given by governments and industry to reducing tail-pipe emissions from Internal Combustion Engines (ICE) in transport system vehicle fleets. The transport sector is one of the largest sources of greenhouse gas emissions and is responsible for approximately one-third of total CO2 emissions globally which has resulted in intensified global warming and climate change. Transitioning away from reliance on fossil-fuel-based energy to Electric Vehicles (EVs) is now seen as an industry-accepted and ready technology to enable meeting challenging emission reduction plans. Wireless charging of Electric Vehicles (EVs) is seen as part of an important strategy to reduce emissions from essential transport trips of people and goods. Resonant Inductive Power Transfer (IPT) is used in the development of wireless charging systems for in-road charging systems. IPT pads are embedded in a pavement infrastructure to create a magnetic field that is coupled into a similar pad fitted underneath an EV. This is then converted to the voltage and current needed to charge the onboard battery. This method enables EVs to wirelessly receive a charge while stationary or in motion. This presentation will report on transdisciplinary research undertaken at the University of Auckland, New Zealand over the last 7 years to accelerate the user adoption and implementation of electrified transport systems.
Abstract. The objective of the present paper is to determine the thickness of bituminous overlay on the top of a flexible road pavement using a mechanistic-empirical approach. The thickness of the overlay has been estimated on the basis of allowable deflection at the overlay-pavement interface to withstand anticipated axle load repetitions during its service life, while the strength of existing flexible road pavement has been estimated on the basis of pavement surface deflection. The pavement with overlay in the present paper has been considered as a two-layered system, which has been transformed into a homogeneous medium by using Odemark’s method to determine the vertical interface stress at pavement-overlay interface using Bousenesq’s theory. The thickness of overlay for different pavement deflection and axle load repetitions have been obtained using present method and was compared with Asphalt Institute method (AI). The rate of increase of overlay thickness observed in the AI and present method for different axle load ranges are reasonably close. Therefore, the sensitivity of pavement deflection on overlay thickness is comparable between the two methods. The Base Layer Index (BLI) has been estimated using a mechanistic approach for different overlay thickness obtained from AI and present method which shows reasonable convergence. The significant convergence of results between two methods justify the reliability of proposed method as a reliable overlay design approach. It was found from sensitivity analysis that the modulus of the bituminous mix is more sensitive to affect the overlay thickness than axle load repetition, if other parameters remain unchanged.
Abstract. The surface roughness in terms of the International Roughness Index (IRI) is critical in assessing pavement quality, affecting vehicle operation costs, driver safety, and comfort. The IRI model in PMED is linear between the initial IRI and other distress. The initial IRI is crucial for IRI model calibration and pavement design. This paper addresses the challenges and data limitations in estimating the initial IRI. It outlines a systematic approach to back-cast the initial IRI, using data from the MDOT sensor database for flexible and rigid pavements. The MDOT sensor database records IRI measurements from 1998 to 2019 for every 0.1-mile (0.161 km) road segment, but the initial IRI may not be available for all sections, especially the older ones. Further, the IRI time series plots show different trends, making having a single back-casting method for all pavement sections impractical. The study employs five distinct methods for estimating the initial IRI, considering variations in measured IRI trends across different pavement sections. A total of 424 flexible and 113 rigid sections were used in this study. A flowchart is provided to help the selection of the most suitable method based on specific criteria. Threshold values are established to ensure reasonable initial IRI estimates for different pavement types and fix types, enhancing the accuracy of IRI models for calibration. The study's findings reveal acceptable initial IRI distributions and time series trends.
Abstract. On cycle paths, surface roughness is one of the dominant measures related to the level of service for cyclists. Then, in recent years, the demand for the maintenance and improvement of cycle path surfaces in-creases in terms of ride quality all over the world. However, the conven-tional approaches to the roughness evaluation are based on the viewpoints of four-wheel motor cars especially in terms of the International Roughness Index (IRI). The purpose of this study is to introduce a concept of a profile-based index which is the Bicycle Ride Index (BRI) suitable for cycle paths considering bicycle vibration responses to the surface roughness. BRI is based on a two degree of freedom model which is compatible with the quar-ter-car model for the IRI. To reproduce the interaction between road surface and bicycle, this study employs four types of bicycles such as hybrid bike, electric hybrid bike, electric city bikes for considering parameters of the model by performing vibration tests. As a result, the bicycles have two res-onance frequencies around 10 and 20 Hz in the body and axle masses as-suming handlebar and front wheel, respectively. This result proves that bi-cycles respond to wavelengths ranging from 0.1 to 1.0 m at normal traveling speed as 15 km/h unlike the conventional definition of “roughness” that covers wavelengths ranging from 0.5 to 50 m. This study also describes the definition of BRI which is applied to the same data accumulation procedure as the IRI.
Abstract. Since approximately 50% of transportation in Japan depends on road vehicles, expressways play an important role in the development of road net-works. However, over hundreds of complaints in a year from road users have been recorded on an expressway call center in terms of the ride quality. Against this background, maintenance strategy of road surfaces en-abling safe and comfort travel is required to maintain a high level of service of expressways. This study identifies pavement surface characteristics caus-ing user complaints in both network and project level analyses of express-way pavements with geographical and profile analyses. The results show that the difference in road surface temperature between daytime and nighttime leads to one of the causes for increasing complaints. This study also proposes the Localized Factor (LoF) and the root mean square (RMS) value of road profile height to visualize localized surface deformation. The outcomes of this study contribute to the improvement of road surface man-agement based on the human-centered design concept that allows road users to travel expressways safely and comfortably.
Abstract. Chip-seal is probably the most widely used surface treatment in the world. Methods for assessing chip seal problems such as chipping loss are dated and rely on qualitative assessment. This paper considers a non-contact method to measure this failure. The method assesses 3d models created and analyzed using UUTex3d. The method of 3d model creation and assessment is summarized. The evolution of areal parameters due to chipping loss is discussed.
Abstract. Acoustical durability is an important factor influencing the ser-vice life of low noise semi-dense asphalt (SDA) pavements in Switzerland. The main factors affecting this property are the reduction in porosity from traffic loadi and especially clogging of pores during the service life. Over the past decade, an extensive database on the in-situ acoustical performance of SDA mixtures in Switzerland has been compiled. The reduction of pave-ment noise relative to dense asphalt measured by the Close-Proximity (CPX) method at various stages in the SDA service life has brought consid-erable benefits to the population living along traffic corridors in terms of noise reduction. However, many SDA sections have underperformed acous-tically. This underperformance has to do with low target voids of the mix-ture designs and the susceptibility of porous SDA to clogging over time. The purpose of the current work is to employ the long-term SDA perfor-mance data to design more acoustically durable SDA mixtures. By inputting in-situ acoustical data collected over the pavement life, the key mix design parameters for good acoustical durability in SDA are derived. It was found that a void content of 15 ± 1% as well as limiting the filler and fines con-tents were consistent with improved long-term acoustical performance. These optimized mixture designs were produced in the lab to evaluate if they fulfill the requirements in terms of Marshall void content and water sensitivity. This study aims to improve on the current Swiss standards for SDA, by refining the mix design method with findings from in-situ data and thereby achieving more acoustically durable mix designs.
Abstract. Flushed road surfacing is a large problem in Australia and New Zealand whom both rely heavily on spray (or chip) seal as a cost-effective wearing course for flexible pavements. Conventional methods for correcting flushed spray seal surfacing can comprise texture reseals or hot chip placement but most typically involves high pressure water blasting of the surface. This essentially removes the flushed/excess binder which also risks reducing the durability and moisture resistance of the seal, making the future remaining life of the surfacing uncertain. Over the last 3 years, Hiway Group has worked through an R&D process to develop a new method for the treatment of flushed seals resulting in a self-contained chip spreader integrated within high-capacity heating banks, named HiTex. HiTex is a technology for the treatment of flushed wearing courses that refines the earlier “Hot-In-Place Asphalt Recycler” (HIPAR) heating banks that were used historically to heat and soften thin asphalt surfacing before insitu recycling. Here the heating of the flushed surface allows a more controlled liquefaction of the binder allowing the sealing chip to be placed and heated for optimum adherence. The innovative process allows the restoration of the macrotexture and skid resistance properties of the wearing course, through correction of the binder/stone volumetrics within the surfacing layer without removal of any of the flushed bitumen. This ultimately improves the life of the pavement as there is less chance of water ingress through the surfacing layer when compared to water cutting. The configuration of the HiTex unit allows for selective treatment of the flushed pavement via single lane wheeltrack, both wheel tracks or where necessary full lane-width treatment.
Abstract. This study focuses on the deterioration of road pavement, particularly the formation of rutting, which adversely affects vehicle braking performance, especially in wet conditions. The research aims to predict the combined effects of rutting and intense precipitation on the vehicle braking performances by using a model based on Back-Propagation Neural Network (BPNN) algorithm. The model calculates vehicle braking distances on wet bituminous pavement, during rainfall with variable intensity, coupled with the effect of rutting, considering the presence of various Water Film Thicknesses (WFTs) over the pavement. It addresses real-world scenarios, incorporating factors like precipitation intensity, lane characteristics, rutting depths, and accumulated WFT. It can be seen that the effect of rutting on vehicle performance, particularly during rainy days when the rutting depressions are filled with rainwater, results in longer braking distances compared to dry conditions. The model's applicability is demonstrated through validations, examining its performance against existing methods. Additionally, the developed model is verified by simulating a vehicle's performance in a real case study, considering varying rutting depths every 10 meters during intense precipitation.
Abstract. Road construction is increasingly using reinforcement additives to improve its durability and performance to ultimately achieve a sustainable infrastructure. Fiber reinforced mixtures have been a promising strategy for enhancing asphalt road performance in recent years, this is especially true for novel road structures like porous asphalt (PA). This study's overarching objective is to experimentally investigate, at low and intermediate temperatures, how fiber reinforcement and aging conditions interact to influence the mechanical properties of porous asphalt at the asphalt mastic phase. First, a porous asphalt, PA 8, was selected as the reference mixture based on an active German standard. Afterward, asphalt mastic was prepared without and with fibers and then aged to different conditions. Two different types of asphalt binders, and two commercially available fibers, aramid and polyacrylonitrile, were used to achieve this goal. Linear Amplitude Sweep (LAS) and Bending Beam Rheometer (BBR) were conducted to evaluate the fatigue and thermal properties. The results indicate that the fatigue and low temperature properties of asphalt mastics are unaffected by the addition of fiber, while the aging condition brings more remarkable influence.
Abstract. This study explores the impact of Phase Change Fibres (PCF) in asphalt mixtures on urban heat control and pavement durability, especially under diverse climate conditions. The incorporation of PCF in pavements offers an adaptive response to temperature fluctuations, presenting a prom-ising approach for urban resilience and sustainable infrastructure develop-ment. The research involves coaxial fibres produced via wet spinning, uti-lizing cellulose acetate for the sheath and Polyethylene Glycol in the core. The Design of Experiment (DoE) methodology aids in determining the op-timal fibre incorporation rate. Asphalt samples with varying fibre contents and lengths undergo testing for heat absorption and dissipation rates. Re-sults indicate that mixtures containing 10 mm fibres at a 0.55% concentra-tion exhibit slower cooling rates compared to non-fibre mixtures, suggest-ing enhanced thermal regulation. These findings point to the potential of such mixtures in mitigating the Urban Heat Island (UHI) effect and improv-ing pavement longevity.
Abstract. This study evaluates the impact of various aging conditioning methods, including the newly developed Universal Simple Aging Test (USAT) and Ultraviolet (UV) aging, against the traditional Rolling Thin Film Oven (RTFO) and Pressure Aging Vessel (PAV), on the rheological properties of asphalt binder. The results reveal that the effects of RTFO and USAT on asphalt binders are comparable for short-term aging. Specifically, the crossover frequency (Ѡc) and fatigue life (Nf) of virgin asphalt (VA) are similarly reduced by 53-55% and 39-41% for both RTFO and USAT methods, suggesting USAT as a budget-friendly alternative for lab aging in absence of RTFO units. In contrast, USAT and UV methods fail to replicate the aging severity achieved by the PAV method for long-term lab aging. This is apparent from the more than 95% reduction in Nf value after PAV aging, versus the 70%-80% decrease with USAT and UV aging. These insights are essential for enhancing the understanding of asphalt binder aging and for selecting appropriate lab aging methods in pavement engineering research and practice.
Abstract. Asphalt modification has played a crucial role in improving me-chanical characteristics of asphalt mixtures, thereby enhancing performance and extending service life of the asphalt pavements. Different combinations of SBS and LDPE modifier concentrations were investigated in this study. Conventional properties, rutting and fatigue behavior were obtained to evaluate performance-related properties of the modified binders. The results show that the LDPE plastomer was more effective on reducing penetration than the SBS elastomer. The SBS elastomer appeared to be less thermal sus-ceptible than the LDPE plastomer over a wide range of test temperatures in terms of G* master curve. The BYET with method A shows the binder with 2% SBS + 4% LDPE possessed the highest yield energy together with max-imum shear stress values. The higher yield energy suggested an elevated re-sistance to fatigue of the modified binders. The addition of SBS elastomer to asphalt would significantly increase the elastic recovery behavior of binders compared to the LDPE plastomer based on the BYET method B. The elastomer had greater contribution to fatigue cracking compared to the modified binder with plastomer in terms of LAS results. The binder with 6% SBS possessed the highest numbers of loading cycle to failure. The ad-dition of SBS elastomer to asphalt binder would help to improve the elastic response at higher temperatures compared to the inclusion of LDPE plas-tomer. It is concluded that the binder with 6% SBS had good performance in fatigue, while binder with 2% SBS + 4% LDPE represented the well re-sistance to permanent deformation.
Abstract. Bituminous mortar contains aggregates passing 1.18 mm sieve, fillers (material passing 0.075 mm) and bitumen. In general, the bituminous mortar is characterized in torsion using prismoidal (rectangular cross-section) and cylindrical (circular cross-section) specimen geometries. The properties of the material vary with the cross-section of the specimen geom-etry used for testing. Non-axisymmetric cross-sections, such as rectangular cross-sections, warp (out-of-plane displacement) when subjected to tor-sion, but this displacement is not allowed in a dynamic shear rheometer (DSR). This leads to the development of additional stresses in the material, known as warping stresses. The warping stresses need to be accounted for to obtain the material's true properties. This study investigates the linear vis-coelastic properties of prismoidal bituminous mortar specimens subjected to torsion using a DSR. A frequency sweep experiment is carried out at three temperatures (10, 20 and 30 ⁰C) for frequencies ranging from 0.01 Hz to 20 Hz. Correction factors such as the Vlasov and Szabó are applied to quantify the amount of warping stress in prismoidal specimens. A percent-age difference is computed between the absolute shear modulus obtained from the DSR and the corrected modulus using the Vlasov and Szabó cor-rection factors. It is observed that the percentage difference after the Vlasov correction varied with frequency and temperature, whereas the percentage difference remained the same after the Szabó correction.
Abstract. Road infrastructures are simultaneously the causes and consequences of socio-economic development of any country. They have crucial importance in operation of the economy, because they stablish the necessary movement of people and goods in a quick, safe, and effective way when they are in a good condition. The decrease in the quality of road pavements is due to the evolution and occurrence of degradation, resulting from the joint action of traffic and weather conditions, and consequently arise the need undertake to conservation / rehabilitation operations in order to restore its structural and functional qualities. To provide the high-level service to users (security, economic, comfort and environmental quality), it is crucial to have knowledge of the condition of the pavement throughout its life cycle. The performance indicators (PI) provide qualitative and quantitative information, concerning the pavement conditions, based on observed and measured pathologies, allowing to identify the need for intervention. Thus, it is important to highlight that in many realities the environmental PI are rarely used in the road sector, with emphasis only on the economic sector. This paper aims to propose environmental, social, and economic performance indicators for road pavement maintenance and rehabilitation works, to be implemented in pavement management systems. The sustainability is achieved after reconciling three main factors: environmental, social and economic. It is not enough for an organization's managers to focus on just one or two aspects of sustainability, but rather, focusing on all three aspects, as each is vital to fully achieving sustainability.
Abstract. Street pavements are subject to various types of distress which necessitate a cost-effective management approach. This paper pre-sents the outcomes of a survey focusing on street pavement maintenance and the utilization of machine learning (ML) pavement performance models on a 320 km municipal street network in Skellefteå municipali-ty, Sweden. The findings reveal that the most common types of distress on Swedish streets include potholes, surface unevenness and alligator cracking, while prevalent causes of these distress are pavement ageing, heavy traffic and pavement patches. The windshield method of assess-ment of street pavement is prevalent, but the use of pavement manage-ment systems (PMS) is limited and pavement performance models are rarely employed. The case study reveals that Random Forest (RF) mod-els developed for non-residential streets perform better than residential street models. RF models based on the variables age (A) and traffic (T) emerged as the best models, with 84% prediction accuracy. However, the R-squared value for the RF model applied to residential streets was 0.53, slightly surpassing the values for all models applied to non-residential streets (0.31, 0.50, 0.49). Further evaluation of models is suggested by using additional data.
Abstract. Transportation agencies are increasingly faced with the challenges of maintaining an aging infrastructure with constrained budgets. Fundamental to that challenge, is the ability to efficiently and effectively establish the condition of road pavements. Recognizing that roads currently make up such a large portion of an agencies transportation system, being able to quickly and qualitatively confirm pavement condition is a significant area of interest. Technology now exists to collect all the traditional pavement characteristics simultaneously, at high resolution, and at traffic-speed in a single integrated evaluation. Collecting continuous structural metrics, geometrics, texture, longitudinal and transverse profile, imagery, and other related metrics provides a more comprehensive perspective on the condition of the pavement, and the opportunity to conduct a more thorough analysis of the pavements’ current status and treatment needs.
Abstract. With the increased number and type of waste collection vehicles using local pavement networks, agencies are interested in implementing vehicle impact fees to recoup costs associated with pavement damage caused by such vehicles. The purpose of this study was to estimate the service life and financial impacts of waste vehicles on local pavements for two contrasting California agencies. A sophisticated methodology was developed combining elements from both the Caltrans HDM and the AASHTO pavement design guide to analyze agency-specific data. The study results indicated that waste vehicles consume approximately 10.1 and 24.1 percent of a residential pavement's life each year in the small city and large county, respectively. Similarly, waste vehicles consume approximately 6.2 and 18.2 percent of an arterial/collector pavement's life each year in the city and county, respectively. The city’s pavement damage is valued at $8,161 per centerline residential mile per year and $6,659 per centerline arterial/collector mile per year. For the large county, the damage is estimated at $6,211 per centerline residential mile per year and $4,735 per centerline arterial/collector mile per year.
Abstract. Local road pavements are often comprised of thin marginal granu-lar material base courses with a thin bituminous surface. When these pave-ments require rehabilitation, new granular reconstruction is the standard historical approach. However, in recent times, stabilisation of the existing pavement has also become popular. This research calculated seven structur-ally equivalent pavement rehabilitations, including a new granular and two stabilised pavement options, each with sprayed seal and asphalt surface op-tions, as well as a full depth asphalt pavement. The social, financial and en-vironmental cost of each was estimated, and a triple bottom line value was calculated. It was concluded that stabilisation of the existing pavement structure consistently provided the lowest cost solution, whereas new granular pavement reconstruction was consistently the most expensive op-tion. It is recommended that existing pavement stabilisation be the pre-ferred existing pavement rehabilitation for local roads, except where other factors render stabilisation unviable.
Abstract. Merimbula airport is typical of regional airports in Australia, with a modest aircraft pavement network comprised of local natural gravel and a thin bituminous surface. The airport pavements were expanded and rehabilitated for larger aircraft in 2022 and this paper presents a case study of that work as an example of sustainable and resilient airport pavement re-habilitation. Novel inclusions were the adoption of new runway starter ex-tensions instead of permanently displaced thresholds within an extended runway length, the objective assessment of four staged pavement develop-ment options for sustainability and resiliency, a triple bottom line ap-proach to pavement type selection, the use of foamed bitumen stabilisation of the existing granular pavement, and the optimization of the mixture deign of that foamed bitumen base for different granular materials. It is recom-mended that other airports take a similar approach to significant pavement rehabilitations, for more sustainable and resilient aircraft pavements.
Abstract. Early rehabilitation is considered an ideal strategy for managing road pavements, as it is expected to ensure longer durability to minimize the life-cycle cost. However, such a practice has not much been adopted, so its effectiveness is even difficult to understand. As a step toward imple-mentation, how many years rehabilitated pavement have so far sustained was investigated, using NEXCO-PMS, which collects not just road surface monitoring data but also all segments of pavement repair projects for dec-ades. In categorizing the projects into groups that have the same rehabilita-tion history on a Japanese toll roadway, a tendency that earlier dates of re-habilitation give longer durability in problematic sections was confirmed, with the assumption that bearing capacity of porous pavement deteriorates fast. It was also revealed that control of road surface indices such as rutting and crack ratio at a lower level is essential. Moreover, in sections where re-habilitation is forced to be done repeatedly, it is important to keep crack ra-tio at a lower level to achieve earlier rehabilitation.
Abstract: This study provides a comparative environmental assessment of two pavement rehabilitation strategies: Full-Depth Reclamation (FDR) and Mill and Fill (M&F). The analysis includes two FDR treatments, each containing bitumen emulsion in combination with a distinct hydraulic binder (active filler). Life Cycle Assessment (LCA) methodology principles are applied to quantitatively assess advantages and disadvantages associated with these techniques. However, the scope of the study is limited to the environmental assessment of the base layer rehabilitation stage, from raw materials extraction until in situ operations requested by the two rehabilitation strategies. The comparative analysis is based on greenhouse gas emissions (GHG) and energy consumption of the rehabilitation processes. Results indicate that FDR significantly outperforms M&F, with a 51% reduction in GHG emissions and a substantial 64% decrease in energy consumption. Regarding FDR solution, the absence of the heating process at the asphalt plant is essential for achieving this performance since it constitutes 53% of GHG emissions in the M&F solution. Choice of sustainable materials may also improve the environmental impact of the FDR opting for a stabilized material with bitumen and low clinker binder. This may lead to even more substantial reductions compared to M&F.
Abstract. This study examines the changes in friction and texture following the applica-tion of shotblasting to an asphalt pavement. The primary aim is to assess both the immedi-ate impact and the lasting effects of the treatment. To achieve this, a road segment featuring an asphalt surface in optimal condition was selected. The segment was then divided into two sections: one treated with shotblasting, and the other serving as a control section with no modifications. Friction and texture measurements were taken at various time points after construction in both sections, providing data to quantify the impact and duration of the shotblasting treatment. In terms of friction, the longevity of the shotblasting appears to be 1.2 years, and for texture, the longevity was closer to 3 years. However, surface texture components were affected by a deicing operation conducted 1 year after shotblasting, which may have influenced, especially in terms of friction, the observed trend in the sec-ond and third year. The results of this study will inform the use of shotblasting as a sur-face treatment to improve skid resistance.
Abstract. Diamond grinding is a process that involves removing a thin layer of the pavement’s surface using closely spaced diamond saw blades stacked on a machine driven shaft. The level surface is achieved by running the blade assembly at a predetermined level across the pavement surface, which produces saw cut grooves. The uncut concrete between each saw cut breaks off more or less at a constant level above the saw cut grooves, leaving a level surface at a macroscopic level with longitudinal texture. Diamond grinding has multiple benefits, includ-ing improved safety, enhanced sustainability, reduced tire/pavement noise, and greater pavement longevity. Research results from multiple studies demonstrate diamond grinding’s value and role in road con-struction and maintenance.
Abstract. Reflective cracking is a critical distress in asphalt overlays. Numerous test methods and modeling approaches have been proposed to predict its severity and/or extent. These approaches range from the purely empirical to highly mechanistic. This presentation briefly reviews these approaches and suggests an experimentally and analytically balanced approach to predict reflective cracking in asphalt overlays.
Abstract. A key factor in assuring the resilience of transportation infrastructure in the future is the consideration of climate change in pavement maintenance and rehabilitation activities. This is a complex issue that requires the collaboration of scientists, engineers, practitioners, and various stakeholders. This talk will introduce some basic information on future climate data, various adaptation frameworks and strategies, and specific applications of these concepts to flexible pavements.
Abstract. NOx emissions commonly emitted by vehicles, pose environmental and health challenges worldwide. Photocatalytic asphalt pavements, used in urban settings, are in close contact with these emissions. In this study, the contribution and role of asphalt mix components—stone and bitumen—were analyzed in the degradation process. The effectiveness of TiO2 coatings on limestone-bitumen composites of varying ratios (100%, 75%, 50%, 25%, and 0%) was assessed using X-ray diffraction analysis (XRD), Confocal Laser Scanning Microscopy (CLSM), Fourier-transform infrared spectroscopy (FTIR), and the modified ISO 22197-1:2016 standard for NO removal. XRD verified the presence of calcite in limestone. CLSM revealed surface modifications and coating morphology, FTIR verified successful TiO2 PF2 coating deposition and NOx degradation quantified the NOx degradation (%), NO degradation (%) and NO2 formation (%) during photocatalytic activity. It was evident that samples with a higher ratio of stone-to-bitumen exhibited an elevated NOx degradation, reaching up to 29.11% for NOx, 43.79% for NO, and 13.96% for NO2 formation. Conversely, samples with a lower stone-to-bitumen ratio recorded values as low as 8.93% for NOx degradation (%), 10.30% for NO degradation (%), and 0.95% for NO2 formation (%). These outcomes firmly establish the inhibitory effect of the bitumen substrate on NOx and NO degradation but a positive effect on NO2 formation.
Abstract. The importance of road pavement durability must not be underes-timated, as it impacts road safety, reduces maintenance costs and environ-mental impacts. The constant exposure of wearing courses to atmospheric agents such as UV-rays or rain, and traffic-induced stresses, contribute to accelerated wear and deterioration. The aging behaviour of the binder used plays a crucial role in the pavement’s durability during its service life. The objective of this study is to investigate the potential of alternative addi-tives to effectively compete with conventional polymers in enhancing re-sistance to UV aging. For this purpose, the effect of two different additives (one natural and one synthetic) on the durability of bitumen was studied. Biochar was chosen as the natural additive and SBS as the synthetic. Two aging methods, thermal and UVB ageing, were implemented to understand which additive would lead to the formulation of a binder that would not only perform better from a mechanical perspective but would also be more durable. The experimental results obtained suggest that biochar has a posi-tive anti-aging effect, though lower than that offered by virgin SBS polymer, and that, for selected applications, it could represent a cost-effective alter-native.
Abstract. Many types of nanomaterial, such as nano-TiO2, nano-Al2O3 are frequently used for modifying asphalt to enhance its pavement performance. However, conventional nanomaterials often exhibit limited compatibility with asphalt. This problem can be improved by using solvent-free nanofluids. Solvent-free nanofluids are engineered by surface functionalization of conventional nanomaterials, allowing them to manifest liquid-like characteristics without the use of solvents. In this study, solvent-free SiO2 nanofluid (SiO2 NFs) was used to modify asphalt, in order to improve the performance of asphalt road while improving the compatibility between nanomaterials and asphalt. Fourier Transform Infrared spectroscopy (FTIR) was used to explore the mixing mechanism of solvent-free nanomaterials and asphalt. The storage stability of modified asphalt has been investigated, and the aging performance of the modified asphalt has been studied from a rheological perspective. Results show that the surface functionalization enhances the dispersion and compatibility of nanomaterials in asphalt, resulting in a homogeneous blend system. The introduction of SiO2 NFs improves the short-term and long-term aging properties of asphalt. Furthermore, the modified asphalt demonstrates some improvements in storage stability. These results highlight the significance of employing SiO2 NFs for asphalt modification to enhance compatibility between nanomaterials and asphalt.
Abstract. Nowadays, road maintenance and rehabilitation strategies repre-sent important budget investments worldwide as a result of the need for suitable pavement structures. The selection of alternative materials for more efficient and durable solutions is therefore imperative through research ini-tiatives and field projects. In response to these requirements, this paper re-ports the main results derived from an experimental study on asphalt mas-tics produced with a combined use of styrene-butadiene-styrene polymer modified bitumen and hydrated lime as a partial replacement of limestone filler. The set of five materials considered were subjected to laboratory tests, to characterize the stiffening mechanism and the performance response in terms of fatigue, thermal cracking and permanent deformation. From the results, some benefits and limitations on the use of hydrated lime as a par-tial replacement of limestone filler were observed, indicating its potential use at optimum filler dosage for pavement locations with warm-to-hot weather as a consequence of the filler stiffening mechanism and its conse-quences on the elastic response to counteract permanent deformation. Fa-tigue cracking results suggested detrimental effects on the predicted fatigue lives for very high hydrated lime concentrations, further suggesting the need of an optimum HL below 10% by total mastic volume. Furthermore, the low-temperature results measured through delta Tc values validate substan-tial improvements in the thermal cracking resistance with the incorporation of HL as a partial replacement of LF.
Abstract. The fatigue life of the bituminous pavement is influenced by the fatigue behavior of each of its constituents. This study focuses on the fa-tigue behavior of bituminous material at two scales: bitumen and mastic. Conventional methods to determine the fatigue life of bitumen using time sweep tests make use of post-processing techniques established for bitumi-nous mixtures and these post-processing techniques make use of linear vis-coelastic parameters for the same. In this study, a new approach based on higher-order harmonic information obtained from a response stress wave-form when subjected to repeated strain-controlled oscillatory shear loading is used. This approach works on the assumption that the occur-rence/evolution of higher-order harmonics in a material exhibiting line-ar/nonlinear response when subjected to repeated loading is attributed to damage. For this, time sweep data at different frequencies and strain ampli-tudes are obtained using the large-amplitude oscillatory shear mode for bi-tumen and mastic under unaged and long-term aged conditions for 20000 cycles. The fatigue life is determined using the new approach involving the use of higher-order harmonics along with two conventional approaches and compared. Also, a fatigue range is established using these approaches to as-certain the influence of strain amplitude, frequency and aging on the fatigue behavior of bitumen and mastic.
Abstract. The research work presented in this paper focused on the evaluation of failure properties of asphalt binders at low temperatures by monotonic torsional loading (MTL) test. By making use of conventional dynamic shear rheometers, cylindrical specimens of binders (4 mm diameter and 5 mm height) were subjected to monotonic shear loadings until rupture at constant temperature and strain rate. The tests were performed at several temperatures and the brittleness index IB was calculated for the determination of the critical brittleness temperatures (Tcr). The investigated materials included four asphalt binders of different origins and types. For comparison purposes, the same binders were tested at the bending beam rheometer for the determination of their low-limiting performance grade (PG) temperature. Analysis of results was conducted with the primary goal of highlighting the differences in terms of performance ranking of materials obtained by using the two methods. The ranking order based on Tcr criterion appeared to be more coherent with the inherent nature of considered materials with respect to PG grading, revealing the ability of MTL test method in capturing the contribution of SBS polymer in enhancing thermal cracking performance of binder.
Abstract. In addition to future raw material scarcity, environmental crises have made scientists and road authorities focus on the sustainability of asphalt pavements more than ever. With this aim, several short-term and long-term techniques and strategies have been set via carbon neutralization plans. Among these strategic plans, both asphalt recycling and Warm Mix Asphalt (WMA) play crucial roles. Each of these techniques are potentially beneficial at different stages of asphalt pavement production and laying. This research represents a case study in Portugal where, for the first time, an asphalt pavement containing 30% of Reclaimed Asphalt Pavement (RAP) was produced as WMA, using a liquid rejuvenator and a mixture temperature lowering chemical product. The produced material was laid in trial sections using traditional construction equipment. The laboratory phases included the mix design, post-production controls, core analysis, and monitoring. The testing plan included conventional volumetric analysis, Marshall stability, tensile strength, stiffness modulus and resistance to rutting parameters, and fatigue endurance tests. When applicable the obtained test results were compared with the technical specifications of two of Portugal’s main roadway authorities. It is noteworthy that, although very high modulus and rutting resistance was recorded, the fatigue performance was better than expected. This could stem from the precise and correct selection of the dosage and the type of the rejuvenator. While some recycling agents i.e., flux oils increase the rutting susceptibility, the used rejuvenator did not impact this crucial structural mechanical parameter.
Abstract. The priority in road construction is to reduce the energy con-sumption in the production of mineral-asphalt mixtures used for the upper layers of pavement structures. The most effective approach in this regard is production of such a mixture in the half warm technology (HWMA) with water-foamed bitumen. It is produced at a temperature 50oC to 70oC lower than that required for the production of traditional mineral-asphalt mix-tures. In the research, AC 8S asphalt concrete was used, made with foamed 50/70 grade bitumen. High values for the foamed parameters of the binder were obtained by adding a surface active agent at a rate of 0.6 wt.% in rela-tion to the bitumen before foaming. In order to ensure the high-quality properties of AC 8S asphalt concrete in the HWMA technology, hydrated lime was used as a substitute for part of the mineral filler. Its influence on the physical (air void content) and mechanical properties (indirect tensile strength, moisture and frost resistance, stiffness modulus, low temperature cracking resistance) of AC 8S asphalt concrete produced in the HWMA technology was studied. Using Harrington's utility function, the optimal content of hydrated lime and foamed bitumen was determined. A compre-hensive evaluation of the results demonstrated synergy between hydrated lime and 50/70 asphalt with the addition of 0.6% surface active agent, en-suring that the HWMA AC 8S mixture meets all the normative require-ments.
Abstract. Together with harmful gas emissions, energy consumption is gen-erally regarded as the main issue in environmental policy. The benefits of reducing energy demand are not only related to lower environmental prob-lems (energy production and usage can be associated with air and water pol-lution, climate change, and solid waste disposal) but are also closely linked to the reduction in the price of road construction and rehabilitation. To this end, the reduction of the amount of energy required at the production stage is gaining momentum. Based on the above, the objective of this study is to investigate the energy required throughout the process of construction of a friction course paved using warm mix asphalt (WMA) technology and in-cluding recycled and waste products in the mixture. Energy impacts (in terms of global energy requirement - GER) are assessed through the main processes from the cradle (acquisition of raw materials) to the gate (friction layer construction included) using a life-cycle method and focusing on the asphalt mixture production stage. Finally, results are compared to conven-tional hot mix asphalts (HMAs). The processes are investigated in order to identify the life-cycle stage and the processes associated with the highest impacts. The main results show that the energy requirement for the solution that includes HMA is approximately 1.2 times higher than that of the alter-native that uses WMA. In particular, because of the higher mixing tempera-ture, the production of the HMA mixture requires an amount of energy that is greater than that demanded for the WMA solution.
Abstract. The elastic and viscoelastic characteristics of Warm Mix Asphalt (WMA) and traditional Hot Mix Asphalt (HMA) are closely compared in this investigation. Motivated by the need to address environmental issues, WMA, which is characterized by lower manufacturing temperatures, efficiently lowers greenhouse gas emissions and energy consumption. Furthermore, by reducing reliance on natural aggregates, the use of Recycled Asphalt Pavement (RAP) in WMA improves sustainability. In this study, WMA15% RAP and WMA30% RAP samples were mixed with 50/70 grade bitumen modified with Sasobit additive, while the HMA samples were mixed with non-modified 50/70 grade bitumen. Through the use of Maxwell model in pony series technique, the study highlights the importance of viscoelastic characterization for precise finite element modelling, highlighting the behaviour of asphalt materials over time. Results of the study shows that elastic characterization in FEM overdesign when compared to viscoelastic while the elastic characterization in Layered Elastic Analysis model under design.
Abstract. In the past, Montmorillonite K10 (MMT K10), an acid-activated clay, was successfully used as a raw material to synthesize zeolite-like warm-mix asphalt (WMA) additive. The major objective of this research was to synthesize a foaming zeolite with bentonite as an alternative to MMT K10 and assess the physicochemical characteristics of additive through fundamental and advanced binder tests on virgin and rubber-modified binders. Fundamental binder consistency tests revealed that the additive modification resulted in stiffer binders, which could offer higher resistance to rutting at higher temperatures. Furthermore, the asphalt mix-tures produced with the WMA additive-based asphalt cement demonstrated a reduction of compaction temperature by 6 C compared to the virgin and rubber-modified mixtures. The WMA additive-based binders offered more resistance to rutting when subjected to traffic loads and elevated tempera-tures as the failure temperatures were higher compared to virgin and rubber-modified binders. Morphological analysis of the synthesized additive con-firmed the presence of hexagonal shaped particles whereas thermal analysis confirmed the release of water into the binder from 70-200 C, consequen-tial of decreasing the viscosity of the binder and production temperatures. Overall, the replacement of MMT K10 with bentonite indeed improved rhe-ological parameters over the conventional binders and mixtures while also being an economical alternative to MMT K10.
Abstract. This article evaluates the viability of cold-in-plant recycling with foamed bitumen for road rehabilitation through a case study on the ER243 road in Portugal, highlighting its alignment with European circular economy principles. The primary objective is to assess environmental benefits, construction efficiency, and the quality of this innovative recycling method as a sustainable alternative to traditional pavement reconstruction. Utilizing 100% of the existing pavement materials and incorporating new asphalt only in surface layers minimizes waste production, reduces material transport, and significantly cuts CO2 emissions. Despite initial challenges due to the lack of specifications and limited application experience in Portugal, the case study demonstrates substantial environmental advantages and potential for quality pavement construction. An estimated 66% reduction in CO2-eq emissions was observed compared to conventional reconstruction, emphasizing lower energy and resource consumption. Quality control tests during the project confirmed the recycled mixture’s satisfactory performance, thus meeting specified limits and showing improvement over time. The findings support the development of expedited material specifications and design methods for cold recycled material layers, aiming to overcome design, construction quality control, and product lifespan assessment challenges, thereby promoting wider adoption of this technology.
Abstract. Compaction quality and density of longitudinal joints are critical to the service life of asphalt pavements. Maintaining deteriorated longitudinal joints has become challenging for many highway agencies. A poorly constructed low-density joint can prematurely distress an otherwise sound flexible pavement, leading to its performance issues in the long run. Longitudinal joints are built using different longitudinal joint geometries, rolling patterns, and construction techniques to achieve better joint compaction. However, each construction technique has its associated risk in making a well-compacted longitudinal joint. In addition, conventional quality assurance (QA) methods like coring and density gauges increase the chances of accepting a poorly constructed longitudinal joint because of limited coverage. This study leveraged the continuous compaction coverage capability of the non-destructive density profiling system (DPS) to identify differences between the joint types and construction techniques. Data analyses show that constructing an unconfined joint should be avoided when possible. Percent within limits (PWL) analysis showed that any joint geometry could produce the least relative compaction differences between a pavement's joint and its mat except for the unconfined joint. Moreover, cutting 4 to 6 inches back from the edge after compaction may result in better compaction of an unconfined joint. Further, PWL results showed that using a smaller subsection/lot can isolate compaction issues locally.
Abstract. Recently, the cost of road repairs increases every year because of an early-age distresses and the fact that the quality of the concrete mixtures produced in a batch plants are not stable. A stable quality control of cement concrete mixtures is very important in construction site. This paper de-scribes the development of quality control equipment and technology using Internet of Things (IoT) technology. Additionally, a database management system (DBMS) was utilized in order to increase the usability and accessi-bility of data. A QR code was adopted to the ready-mixed concrete delivery system from a batch plant to a job site, enabling the data to be cached at a glance. A rheological properties of concrete mixture was investigated through a Twin Shaft Rheometer Mixer, which enables the analysis of con-crete rheological properties. In addition, the quality control of concrete pavement was carried out at a job site using a unit water quantity tester and a chloride content tester, which enables transmitting the measured data at a job site in real time through the Bluetooth reception function. As a result, this research could lead to the development of equipment incorporating IoT-based Quality Control system. Moreover, the development equipment yields more precise data in real time compared to the existing equipment.
Abstract. Highway concrete pavement infrastructure built in California during the 1960s-1970s required major rehabilitation by the end of the 1990s. Due to increasing traffic and impact on users caused by long-term closures, the California Department of Transportation (Caltrans) was forced to look for novel strategies to repair highway pavement quickly. Following the successful completion of pilot projects, Caltrans embraced the use of Rapid-Setting Concrete (RSC) with Belitic Calcium Sulfoaluminate (BCSA) cement, setting a precedent subsequently followed by other states. Despite increased use, the durability and long-term performance of RSCs have faced skepticism. This likely stems from a limited understanding of the behavior of such materials over years or decades of service. It is true that some rapid-setting concrete exhibit early cracking that may be due to thermal effects or high shrinkage due to high cement content. In the first section, this paper explores the material properties and characteristics of BCSA, a type of RSC, highlighting its potential to last for decades of service if designed and constructed properly. The second section details projects constructed 5-15 years ago in various climates, under varying traffic volumes and different concrete delivery approaches. Lastly, a forensic analysis conducted on the oldest BCSA highway pavement section in California rehabilitated in 1997 is discussed, showing that BCSA concrete tripled its strength after 23 years in service.
Abstract. Cold mix patching materials (CMPMs) have become increasingly popular solutions for the emergency asphalt repairs of small- to medium-sized potholes in severe winter conditions or where short reopening times are required. Their performances need to be carefully monitored in the early post-application phases, when these materials have a high potential to face several distresses. The research aimed to identify a set of methods for the rapid and cost-effective acquisition of asphalt pavement surface geometric data to analyze the effectiveness of a given CMPM, with particular attention to procedures that minimize interference with the normal traffic flow or lim-it the lanes closure whilst ensuring the safety of operators and pedestrians. A road trial section in a sub-urban industrial zone, where ideal potholes were cut and filled with different types of CMPMs, was set up for this pur-pose. A low-cost unmanned aerial vehicle (UAV), was used for the experi-ments, repeating the drone survey in four successive epochs (up to 30 days). The captured images were post-processed with a photogrammetric software and the co-registered point clouds at the different epochs were compared to highlight the early patches performances and deteriorations. This ready-to-use methodology, tailored on the urban scale, made it possible to identify over time the occurrence of raveling on the patch area and to monitor the trend of patch surface depressions, extracting desired transverse and longi-tudinal profiles.
Abstract. Anti-oxidation is one of the important functions of preventive maintenance for asphalt pavements. The major working principle of preven-tive maintenance’s anti-oxidation is to retard the entrance of oxygen into the asphalt pavements. To advance the quantitative evaluation of preven-tive maintenance’s oxidation resistance, this study investigates the feasi-bility of using the oxygen diffusion coefficient (Ds) of asphalt mixtures to characterize the oxygen-retarding efficiency of preventive maintenance. Specifically, the fog seal, slurry seal and chip seal were selected as the rep-resentatives of asphalt pavement preventive maintenance techniques to prepare surface treated asphalt mixtures. The Ds before and after being treat-ed by these three maintenance techniques were compared to present the ox-ygen-retarding efficiency of preventive maintenance.
Abstract. Narrow trenching on road pavement has become a widespread practice for installing telecommunication infrastructures on road pavements. Although such technique guarantees a social and environmentally sustainable construction, the quality of the backfilling plays a crucial role in both the short- and long-term properties of the trench. In this context, the present research aims to assess the effectiveness of a cement-bitumen emulsion grout (CBEG) as unique backfilling material for narrow trenches. To this purpose, a real-scale field trial was constructed and monitored through visual inspection, coring activity, and permeability tests. Skid resistance tests, compressive and flexural strength tests were also carried out on specimens casted in the laboratory. Moreover, indirect tensile strength tests were performed to evaluate the adhesion properties at the existing pavement – backfilling interface on both cored and laboratory moulded specimens. Results mainly show that the CBEG, due to its flowable nature, quick hardening, and great early strength, provides uniform backfilling and fast restoration of the pavement surface. The latter shows skid resistance values comparable to those of hot mix asphalt pavement. After long curing, the backfilling does not show any lowering phenomenon and ensures adhesion at the interface as testified by the absence of water penetration. Finally, a satisfactory adhesion at the interface is determined also in terms of indirect tensile strength.
Abstract. The adhesion behavior between crumb rubber (CR) modified asphalt binder and aggregate interface is more complicated due to the incorporation of crumb rubber. This paper focuses on the changes in the interfacial chemical structure and the SARA fractions transformations during the adhesion of the CR modified asphalt binder to the aggregate. A new iso-mass layered extraction process was proposed to obtain different layers of CR modified asphalt binder on the aggregate surface. Afterwards, the SARA fractions and molecular weight distribution of each layer of binder was studied by gel chromatography (GPC) test, SARA four-component separation test and thin layer chromatography-flame ionization detection (TLC-FID). The results show that the changes in interfacial structure and molecular weight distribution due to the adhesion process continue from the innermost layer to the third elution layer on the aggregate surface. From the outermost layer to the eluted layer near the aggregate surface, the asphaltene content increases significantly, the saturate content decreases significantly, the resin content decreases slightly, and the aromatic fraction content varies insignificantly. Additionally, the closer to the adhesion contact surface between the aggregate and the CR modified asphalt binder, the higher the number of macromolecules, which reaches a maximum in the innermost layer.
Abstract: The process of recycling scrap tire crumb rubber into asphalt pavements has been under continuous improvement for decades. Start-ing as early as the 1950’s various means and methods of incorporating recycled crumb rubber in asphalt have been proposed and applied in var-ious test sections. Starting in the 1970’s patented and proprietary as-phalt rubber products were developed and began to be used in several states, including Arizona, California, Texas, and Florida. These prod-ucts were described as a dry and wet process. The dry process adds crumb rubber to a hot asphalt mix as a rubber aggregate filler and for various reasons is seldom used today. The wet process mixes the crumb rubber with hot asphalt to make a rubberized asphalt binder. The wet process is also widely used throughout the world for seal coating, crack sealing and in all types of hot asphalt mixes. Reacted and activated rubberized (RAR) asphalt is a relatively new material incorporating the good properties of both the wet and dry processes, namely ease of use and quality performance. This paper describes the many advantages of RAR products that are well suited to meeting the challenges of a resili-ent society for an environmentally sustainable future.
Abstract. In recent decades, the growth of road transport systems has contributed significantly to global warming and environmental pollution. In addition, the constant increase in transport vehicles also implies the generation of a significant amount of end-of-life tires (ELTs) to be landfill disposed. In this framework, the combination of warm-mix asphalt (WMA) technology with crumb rubber (CR) from ELTs, seems to be a valid and sustainable technical solution. Furthermore, the use of CR in asphalt mixtures has proven to improve pavements’ acoustical performance. In this context, the present research shows the results of a laboratory characterization of a dry rubberized semi-porous asphalt mixture produced with WMA technology aimed at optimizing an eco-friendly and low-noise solution for motorway pavements. To this end, several WMAs (with different bitumen and CR content and a reference WMA without CR) were tested and qualified by means of testing for mechanical analysis (Compaction Energy Index, Indirect Tensile Test, Cantabro Test, and Indirect Tensile Stiffness Modulus) and for surface properties detection (by Darmstadt Scuffing Device and Wehner-Schulze machine). Traditional test results show that the workability and mechanical performance of optimized warm mixtures with CR are comparable to those of the reference one. Also, surface test results show adequate values of raveling resistance and friction after polishing, demonstrating that warm mixtures with CR can be considered as a green feasible technical solution for motorway pavements.
Abstract. The use of crumb rubber as a binder modifier in spray seals and asphalt applications is a mature technology that is generally well under-stood for high crumb rubber dosages. However, recent efforts to repurpose end of life tyres must also consider other applications. The use of crumb rubber as a low dosage binder modifier for local roads in Australia has been of significant interest in recent years. To determine their effectiveness as an alternative to more conventional unmodified binder grades, the performance of low dosages (5-15%) of crumb rubber modified binders, using both short and long blending durations, was assessed across several bitumen perfor-mance properties. While a higher (15%) dosage of crumb rubber, and using short blending processes provided the most significant performance im-provement as an elastomeric modifier, the incorporation of any crumb rub-ber using either digestion duration was found to improve base binder prop-erties, and may be suitable for use in local road asphalt surfacing.
Abstract. Mechanical characteristics of asphalt binders and asphalt mixes can be improved by utilizing asphalt modifiers. Crumb Rubber Modification (CRM) of asphalt mixes has been practiced as an environmental friendly approach for improving mechanical characteristics of asphalt mixes. Crumb rubber enhances fatigue life and rutting resistance of asphalt mixes and decrease their moisture susceptibility. Processed crumb rubber is produced using activated mineral stabilizers and hydrated lime. In the current study the effects of PCR and CRM was evaluated on fatigue and rutting resistance of asphalt mixes. For this purpose, CRM containing mixes (at 20% CR level) were prepared. PCR containing mixes at 20, 25, and 30% CR levels (at percentage of bitumen) were prepared. The evaluation method was consisted of testing cylindrical and slab samples at intermediate and high service temperatures. Samples were tested under Semi Circular Bending (SCB) test at 25⁰C and Hamburg Wheel Track (HWT) test at 40 and 50⁰C temperatures. SCB and wheel-tracking tests were carried out on dry and wet conditioned samples. Based on the obtained results, it was concluded that mixes containing both CRM and PCR materials showed significant enhancement, compared with conventional HMA mixes. The findings of fatigue and rutting tests showed that samples containing 25% PCR exhibited the best.
Abstract. Moisture-induced durability distresses are the key barriers of rubberised asphalt that impede its further application. It is of vital importance to understand the adhesion properties between rubberised binders and aggregates. This study aims to investigate the effects of rubber type, aggregate type and water presence on the interfacial adhesion and debonding properties of the bitumen-aggregate system through molecular dynamics simulation. Results show that the bitumen-aggregate adhesion and debonding behaviours strongly depend on the chemistry and mineralogical properties of the aggregates. Alkali aggregates (e.g., albite and calcite) have stronger bonding with bitumen than acid aggregates (e.g., quartz). By comparison, rubber modification has limited effects on the adhesion properties. The presence of water reduces the adhesion of bitumen-aggregate system. The deterioration degree in adhesion depends on the bitumen-aggregate combinations. The findings in this study can potentially be used for guiding the selections of rubberised bitumen with different aggregates to optimise the mixture performance.
Abstract. Cold In-place Recycling (CIR) is a rehabilitation treatment that restores a flexible pavement structure. While there has been significant re-search in design and performance testing of CIR, there is limited considera-tion of performance during construction. This research validated the Stiff-ness Raveling Mechanism Test (SRMT) in the lab and in the field, as an in-expensive, easy way to quantify the curing of CIR. In the lab, CIR and Hot Mix Asphalt showed lower rebound heights at higher air voids, higher test-ing temperatures, and moisture conditioning. In the field, the SRMT had a good correlation to density during compaction, but the data was not accu-rate enough to establish roller pattern recommendations. The SRMT had a maximum rebound after approximately 20 hours of curing and then saw a small decrease over a five-day period, and was able to differentiate emulsi-fied asphalt types based on cohesion gain. Finally, based on the 24-hour field validation, it is recommended that a rebound height of 305-356mm (12-14 inches) could be specified for return to traffic.
Abstract. Cold recycling is a technology used in constructing or rehabilitating flexible pavements. It strives to optimise the performance of processed reclaimed materials and construction methods, in order to gain environmental and economic benefits i.e. reducing carbon footprint whilst improving pavement life. The technology leads to the production of Bitumen Stabilised Materials (BSMs), a base layer that provides sufficient bearing capacity for a spectrum of moderate to very high volumes of traffic. Key considerations for sustainability of BSMs include durability i.e. resistance to moisture damage of materials, and performance i.e. appropriate materials to withstand the traffic loading and environment whilst achieving the design pavement life. This study comprises a combination of three separate research projects, covering BSM mix types and compositions as well as compaction techniques. The two different mix types are BSM-foam, where foamed bitumen is injected to the mix and BSM-emulsion, where the bitumen is emulsified before being dispersed in the mix. In addition Reclaimed Asphalt or RA is included as one of the mix component variables. Three laboratory compaction methods i.e. vibratory, gyratory and falling weight, are utilized in preparing specimens for testing. The compacted specimens were evaluated for the achieved densification, as well as ITS tensile strength and triaxial properties i.e. Cohesion and Friction Angle. The findings show that the application rate of RA in the BSM mix influences the moisture resistance positively and hence durability. Low RA contents provide mixes that perform well with vibratory compaction due to the packing mechanism, whilst high RA contents prefer gyratory compaction, due to the kneading effect. Triaxial tests show that a balance between shear strength and moisture resistance need to be considered in mix designs. In addition, QC can be effectively carried out on the jobsite by stacking 2 or 3 specimens for triaxial testing as opposed to ITS tests being used.
Abstract. A summary of literature on performance testing of Full Depth Reclamation (FDR, also known as Bitumen Stabilization) is presented in this paper. FDR is an important pavement rehabilitation treatment that can eliminate severe distresses and improve pavement structure, while using environmentally friendly techniques. FDR can be considered a semi-bound material (when stabilized with asphalt emulsion or asphalt foam) or a semi-rigid material (when stabilized with cementitious material). Performance testing of FDR has roughly followed that of traditional asphalt mixtures over the past forty years, with a time lag of approximately ten years, and has also incorporated several test from soil mechanics. Water in the FDR, cur-ing time, curing state, curing temperature, and final testing conditions are of upmost importance, and there are not a consistent guidelines for these. In addition, the three stabilization methods of FDR behave very different, and existing asphalt mixture or soils tests may need to be modified to test FDR.
Abstract. Globally, transportation agencies are adopting reclamation and recycling strategies for their rehabilitation and construction needs. Cold recycling technologies are regarded as a sustainable approach for rehabil-itating flexible pavements, primarily due to their economic and envi-ronmental benefits. Cold in-place recycling (CIR) as one method in-volves reclaiming a portion of the distressed asphalt layer and incorpo-rating stabilizing agent(s) into the formation of a new base layer. Re-search has shown positive indicators from the use of recycling agents (RA) to treat reclaimed asphalt pavement (RAP) while using them in traditional asphalt mixtures. The impact of RAs on the performance improvement of cold recycled mixtures remains a subject of ongoing re-search. This study assesses the performance of a conventional and RA-treated CIR pavement towards perpetual pavement characteristics. Four test sections were constructed, differing only in the inclusion of RA in two of the test sections, and the existence of stabilized full depth recla-mation (SFDR) sub-base layers in two sections. These sections were subjected to Falling Weight Deflectometer (FWD) tests, spanning a pe-riod of four seasons on the outer wheel paths in both driving and pass-ing lanes following construction and exposure to vehicular traffic. The findings from the back-calculation analysis, when comparing two sec-tions showed that the RA affected the CIR layer's stiffness whereas for two other compared sections, no discernible change in the CIR layer was observed. Perpetual characteristics analysis indicates potential for bottom-up fatigue cracking in all sections, necessitating an optimized design in terms of Hot Mix Asphalt (HMA) and CIR layer thicknesses.
Abstract. This study explores the industrial-scale production and applica-tion of asphalt mixtures incorporating high rates of recycled concrete aggre-gates (RCA), steel slag aggregates (SSA), and reclaimed asphalt (RA). With a dedicated focus on sustainability within road construction, the investiga-tion scrutinizes two specific asphalt mixtures through a comprehensive field trial section. The findings reveal strict adherence to nationally speci-fied standards, and the water sensitivity tests demonstrate excellent per-formance. The structural evaluations of the pavement trial, utilizing both Light Weight Deflectometer (LWD) and Falling Weight Deflectometer (FWD), demonstrate a commendable load-bearing capacity. However, sur-face characterization tests reveal a lack of skid resistance, a problem ex-pected to be solved after the bitumen surface film has worn off with in-creased traffic volume. This research underscores the critical importance of an exhaustive evaluation of pavement trials with new materials, providing concrete evidence for their practical application and supporting the ongoing paradigm shift towards sustainable practices in road construction.
Abstract. The maintenance and rehabilitation of road pavements consume high annual budgets from road administrations, are associated with a huge production of waste, and consequently a large use of natural resources. In this way, the multi-recycling of reclaimed asphalt pavement (RAP) presents itself as a solution to part of the problem, thus avoiding its classification as waste and consequently landfill.It is necessary to use rejuvenators throughout the successive recycling cycles to recover the properties of the RAP’s bitumen fraction, so if different rejuvenators are used in successive recycling cycles, their interaction must be evaluated. To evaluate the inter-action between two rejuvenators of different origins considering two recy-cling cycles in RAP mixtures with high incorporation rates (75%) for wear-ing courses, laboratory tests were carried out to characterise the rejuvenated bitumen blends, and the bituminous mixtures regarding the mechanical properties, surface characteristics and volumetric properties.The results were compared with a previous case study where were evaluated three AC 14 surf 35/50 mixtures: one with virgin materials, and two with 75% RAP incorporation recycled one and two times with the use of a rejuvenator. Therefore, the interaction between two different rejuvenators, from similar samples, in the same recycling cycle, did not present significative variations in the tests and characteristics of the RAP, demonstrating good compatibil-ity between the rejuvenators.
Abstract. The evaluation of the structural condition of a pavement is of great importance, since pavements are important transportation infrastruc-tures that should have an adequate bearing capacity. For this reason, the use of Non-Destructive Testing (NDT) systems has gained worldwide ac-ceptance as an effective tool for determining pavement condition. Various indices from deflection measurements using systems such as the Falling Weight Deflectometer (FWD) can provide an overview of the structural condition of the pavement. However, detailed and accurate information about the mechanical properties of the individual layers of a pavement can be obtained using advanced analysis tools such as the back-analysis meth-od. The back- analysis method usually requires extensive experience and additional computational resources, which makes it unattractive for general use. With this in mind, the present study attempts to develop a simplified method for a quick and reliable estimation of the mechanical properties of a flexible pavement using established indices such as Surface Modulus calcu-lated directly from deflection measurements with a view to expediting the pavement condition assessment procedures without the need of time-consuming analyses. To this end, NDT data collected along a flexible pave-ment are analyzed and the correlation of the Surface Modulus with the elas-tic modulus of each layer of the pavement is investigated. The study demonstrates the potential of using the Surface Modulus to predict the elas-tic modulus for evaluating the structural condition of a flexible pavement bypassing the use of sophisticated tools.
Abstract: Longitudinal cracks can influence the spread of stress in pavement structure, thereby affecting the pavement deflections. The effects of longitudinal cracks on the falling weight deflectometer (FWD) deflections of pavements with granular base (GB) were investigated and evaluated in this study. The finite element method (FEM) was used to simulate the intact and longitudinal-cracked pavements with GB undermeasured data. Various crack locations, crack widths, asphalt concrete (AC) layer thicknesses, and subgrade moduli were considered in this study. Comparison between the FWD deflections of intact and cracked pavements shows that longitudinal cracks close to the loading center can have significant effects on the deflections of pavements with GB, and the deflections of cracked pavements can be 25% greater than those of intact pavements. The effects of longitudinal cracks are negligible when cracks are located at more than 0.6 m away from the loading center. In general, the influences of crack width on deflections can be ignored. Longitudinal cracks have greater effects on the deflections of GB pavements with a thicker AC layer and a softer subgrade.
Abstract. This study conducted in Kitchener, Ontario, presents a comprehensive analysis of monitoring the environmental and structural behaviour for two years in an instrumented pavement test section. Focusing on pressure, strain, moisture, and temperature measurements throughout the pavement structural layers, the re-search uncovers nuanced patterns. Temperature fluctuations exhibit distinct daily and seasonal variations, with depth-related temperature and moisture changes within the pavement structure. Moisture measurements reveal varia-tions across layers, aligning with precipitation patterns. Load assessments indi-cate consistent pressure variations, with some unexpected deviations between right and left sensor arrays. Strain analysis validates the impact of asphalt mat temperature and strain magnitudes (Granular materials and Hot Mix Asphalt), emphasizing temperature's influence on pavement behavior. Overall, this study provides valuable insights into the reliability of instrumentation data, dai-ly/seasonal variations, and the complex interplay of environmental factors in pavement performance.
Abstract. Pavement-integrated dynamic wireless power transfer (DWPT) can deliver electrical power to electric vehicles (EVs) as they transverse the roadway. However, a thorough investigation is needed to assess the mechanical behavior of pavement structures containing DWPT components. For the work reported herein, a flexible pavement with embedded DWPT components was constructed in an accelerated pavement test (APT) facility to investigate the influence of the embedded unit on the pavement’s mechanical response. Strain gauges were installed at selected locations around the DWPT unit, and pavement responses were measured under static loading to assess the influence of the integrated DWPT unit and the position and alignment of the load. The results show the influence of the DWPT unit’s higher stiffness, as well as the load placement position on the pavement’s strain distribution. The increased stiffness of the DWPT unit correlates with reduced strain levels.
Abstract. Performance monitoring of highway infrastructure is vital for the integrity of the transport network and the safety of the users. The satellite remote sensing technology can task itself to further enhance the standards and monitoring capabilities of Non-Destructive Testing (NDT) methods, in terms of allowing full network-level coverage and a regular revisit of the infrastructure. However, applications are still limited and not yet well established in the operative processes implemented by the asset owners. In this study, the Multi-Temporal Synthetic Aperture Radar (MT-InSAR) approach was utilised to assess the condition of a rural motorway primary connection road to Rome, Italy. Medium (Sentinel-1 (C-Band)) to high-resolution (TerraSAR-X (X-Band)) SAR data were used to analyse and evaluate the surface regularity. More specifically, the Persistent Scatterers Interferometry (PSI) approach, following the algorithm proposed by Ferretti et al., [1] through the approach proposed by Hooper et al., [2] was employed. The proposed methodology uses open-source software for all the entire procedure. The displacements detected by the PSI approach were analysed, and their correlation with the pavement condition in particular sections was investigated across the utilised satellite data resolutions. Changes in the pavement surface condition were categorised based on the estimated deformation rate. The proposed approach will give first-hand input towards network-scale road infrastructure monitoring and will pave the way to explore further the capability of Radar Satellites in this area of science.
Abstract. Integrating new technologies in civil engineering has gained more space, particularly in pavement engineering. By overcoming some gaps that older strategies present, such as purely visual inspection, and by transforming the roads into a structure connected to network managers that permanently transmits data, it is possible to get a better knowledge and understanding of how pavements evolve. This work presents the results of a pavement monitoring system based on optical sensors. These Fiber Bragg Grating (FBG) sensors allow collecting information about the temperature and strains that occur at the bottom of the bituminous layer, assessing the pavement response to the passage of vehicles and the influence of temperature in the measurements made. This system has proven to be very reliable in calculating the speed of vehicles and the characteristics of their axles (distance and type). In addition, the possibility of drawing their deflection basins is a crucial factor in the analysis of the vehicle loads. An automated analysis through algorithms with a comprehensive time base will allow meaningful conclusions to be drawn about the pavement’s performance in the long term, resulting in a better understanding of its behavior.
Abstract. The major purpose of this study was to address the challenge of managing solid waste by assessing the compatibility of waste plastic-modified asphalt-rubber binders through rheological and morphological analyses. Blending operations incorporated varying proportions of crumb rubber (CR) and polyethylene terephthalate (PET) into the base asphalt binder covering six different compositions of CR and PET. Further, the ef-fect of CR and PET waste on binder properties was assessed through fun-damental binder consistency tests, which helped optimize the dosage of plastic-rubber combination in asphalt cement. Rheological tests encom-passed Penetration, softening point, viscosity, and multiple stress creep re-covery (MSCR), which assisted in investigating the viscosity-temperature susceptibility of the asphalt binders. Morphological assessments using high-resolution scanning electron microscopy in conjunction with energy-dispersive X-ray spectrum provided insights into the internal structure and interface bonding of CR, PET, and asphalt binder. Notably, blends with 10% CR and 5% PET exhibited enhanced rutting resistance and improved viscoelastic properties compared to the base binder. The MSCR test high-lighted that the blends with higher CR and lower PET content contributed to improved viscoelastic properties. Conversely, the blend with higher PET and lower CR exhibited poor recovery at high strains, indicating lower re-sistance to rutting. The findings underscored the potential of specific CR-PET combinations in developing resilient and sustainable asphalt binders, emphasizing the need for further exploration in this domain.
Abstract. The use of Reclaimed Rubberised Asphalt Mixtures (RRAM) in road pavement construction is a significant stride in reducing reliance on new materials and reducing waste disposal. RRAM provides a sustainable, cost-effective solution for roads, boosting durability and performance while supporting environmental causes [1,2]. However, despite its benefits, challenges remain. A thorough exploration of recycling RAM into RRAM is crucial. This study investigates into this, aiming to evaluate RRAM recy-clability through a tailored three-step procedure: 1) laboratory production of RRAM, 2) designing RRAM asphalt mixtures using the SUPERPAVE5 concept, and 3) performance-based characterization of RRAM. This compre-hensive approach assesses rutting, cracking, and moisture damage re-sistance. The results highlight RRAM's potential benefits in road construc-tion, shedding light on its recyclability and paving the way for future sus-tainability-focused research in road-building practices.
Abstract. This study was conducted to assess the time evolution of the lin-ear viscoelastic behaviour of bituminous mixtures containing crumb rubber added by dry process. For this purpose, three mixtures containing 0% or 4% of rubber and with neat 35/50 pen grade or SBS-modified bitumen were manufactured and stored for 15 months before being subjected to complex modulus tests. The results were compared to those obtained from a previous study that investigated the linear viscoelastic behaviour of identical mate-rials but tested shortly after their production. The outcomes reveal no sig-nificant evolution for mixtures with neat 35/50 pen grade bitumen and 4% of crumb rubber. However, a potential evolution (ageing or bitumen-rubber interaction) is observed for mixtures with 4% of crumb rubber and SBS-modified bitumen. This study provides valuable insights into the long-term performance of rubber-modified bituminous mixtures, highlighting the need for further investigation into the factors influencing the material's behav-iour over time.
Abstract. Asphalt-rubber can be produced following three main types of methods: the “wet method”, the “dry method” and the more recent “semi-wet” method, each one with their own variations. As long as an adequate technical and economical assessment is performed, these methods of as-phalt-rubber production might have their own space, as they have different costs and specific equipment demands that might suit different projects´ characteristics. Traditionally, the “dry” method has been less used world-wide and the present specifications for asphalt-rubber mixtures from the Portuguese road administration authorities don´t take it into consideration. The main objective of this work is improving the knowledge of asphalt-rubber production in Portugal by presenting the mix design of an open-graded asphalt-rubber mixture by “dry” method complying with all the same properties listed in the specifications for the equivalent mixture by the prescribed “wet method” (the same mixture by “dry” and “wet” method will also be compared). All the different factors impacting the interaction between rubber and bitumen that were defined and taken into consideration in the “dry” method design are presented so that further studies can be com-pared with the present one.
Abstract. Fourier Transform Infrared Spectroscopy (FTIR) has emerged as a powerful tool for evaluating the performance of asphalt binders. Its ability to analyze both the chemical composition and molecular structure of mate-rials provides essential insights into the changes that occur during the bi-tumen modification process. A key area of application is the investigation of shared components in bitumen modified with rubber. Recently, the mod-ification of crumb rubber bitumen has shifted from the wet process to the dry process, which involves pre-activation of the crumb rubber surface, re-sulting in what is known as Reacted and Activated Rubber (RAR). Since the modification process entails both physical and chemical interactions be-tween the components, analyzing these interactions is crucial, and FTIR emerges as a viable tool for this purpose. This study focused on analyzing crumb rubber modified bitumen with varying rubber content, examining the chemical changes and correlating them with performance-related parameters. The findings indicate that FTIR can be effectively used as a fingerprint tool for crumb rubber modified bitumen. It also suggests that the modification process, particularly when using RAR, is more of a physical process than a chemical one.
Abstract. The asphalt rubber wet process is a practical means of providing environmental, economic, sustainable, and safety of using crumb rubber from recycled tires using the wet method technology widely used in societal benefits. New imaginative and innovative engineering technology concepts have led to the development of a new asphalt rubber, crumb rubber semi wet method material with reacted and activated rubber (RAR). The RAR semi-wet process has demonstrated a product capable of matching and surpassing the performance of traditional hot mix asphalt and the traditional asphalt rubber, crumb rubber method asphalt. The RAR dry filler when it meets hot asphalt amalgamates in such a way as to become like the traditional crumb rubber method asphalt rubber. The RAR is superior to the traditional asphalt rubber, crumb rubber method since it can be used at higher percentages. This paper introduces the concept and some experiences of using a RAR binder in asphalt thin gap mixtures applied with or without an RAR stress absorbing membrane interlayer (SAMI). The paper presents how the added flexible fatigue cracking resistance of these mixes leads to great environmental benefits. It introduces key concepts that can be the basis of specifications that can be used by road departments to ensure, not only that the crumb rubber is properly reacted and treated, but that the mixes have adequate bitumen and RAR to satisfy flexural/reflective fatigue cracking resistance.
Abstract. Despite the success of asphalt rubber in pavement performance, its primary concern is related to its production, which requires a specific plant to produce the asphalt rubber contiguous with the asphalt plant. Also, the storage stability presents some issues, mainly due to the segregation of the rubber and the digestion process that does not stop during this time. Thus, searching for new technologies for using crumb rubber in the asphalt has led to a hybrid method through the pre-treatment of the crumb rubber and a subsequent application in the dry process. This treatment produces the Reacted and Activated Rubber (RAR), a crumb rubber coated by a mastic of bitumen and filler. The mechanical performance of the RAR mixtures is related to the amount of modifier crumb rubber added to the base bitumen, so it is essential to study this influence by the performance test. Thus, this paper explores the viscosity and the rheological performance of asphalt binders with RAR by varying the amount added to the base bitumen. For a scale analysis, this work is extended to the study of the effect of RAR on mastic behavior.
Abstract. In Canada, sustainable transportation strategies such as changes in vehicle technology, travel patterns and fuel have been made to reduce vehicle emissions and their impacts on human health and the environment. However, recent studies show that pavement surface condition can have significant effect on transportation fuel consumption and emissions. The rolling resistance effect that occurs during vehicle and pavement interactions can lead to excess fuel consumption and consequent pollutant emissions. Thus, pavement management can provide opportunities to improve fuel economy, and reduce the associated air pollution and greenhouse gas emissions from road transportation. A new Ontario-specific excess fuel consumption and environmental damage cost model recently developed to quantify the energy and environmental impacts from roads provides the opportunity to incorporate these effects in pavement management decisions. The proposed output-based environmental damage cost (EDC) models provide relationship covering environmental impacts of road surface and speed and the associated five atmospheric pollutants - Carbon dioxide, Carbon monoxide, Nitrogen oxides, Sulphur dioxide and Particulate matter 2.5um emissions from seven vehicle types. According to the model, at an average speed (80km/h) a unit increase in IRI (1m/km) can lead to $0.03 and $0.01 per kilometer of EDC for a passenger car and Truck emissions. A case study is presented to explore the effectiveness of EDC of road surface as a short-term policy. Main finding shows that potential savings from pavement roughness can be up to 17% while the application of only recycling retreatment accounts for about 15% of the potential savings.
Abstract. The Lifecycle Cost Analysis (LCCA) is an essential tool highway officials use to evaluate the merits of different pavement design alternatives and make suitable transportation investment decisions. However, the LCCA uses inputs that are inevitably highly uncertain. The deterministic LCCA approach is easy, uses average input values, and is straightforward to determine the low-cost pavement alternative. However, it cannot consider the uncertainty of inputs and can result in ill-informed investment decisions. Further, deterministic LCCA for perpetual pavements designed to serve 50+ years makes the decision-making challenging. The LCCA results presented in this paper illustrate the advantages of the probabilistic approach. Considering the uncertainties in the LCCA inputs due to data shortages or estimation errors, using probabilistic LCCA in pavement design is vital, especially for alternative comparisons involving perpetual pavements. The ability of the probabilistic approach to enable the user to choose the desired level of risk in decision-making and the scarcity of data for the perpetual pavements makes the use of probabilistic LCCA more attractive. In addition, the ability of probabilistic analysis to investigate what-if scenarios can determine suitable and optimum situations where perpetual pavement construction would result in cost savings.
Abstract. In the context of sustainable road construction, this study con-ducts a Life Cycle Assessment (LCA) to evaluate the environmental impact of an innovative asphalt mixture incorporating Steel Slag Aggregate (SSA) and Reclaimed Asphalt (RA), with a specific focus on the production phase. The research compares this innovative mixture with a conventional one uti-lizing Natural Aggregate (NA) and emphasizes the efficient utilization of re-cycled materials in the pavement industry. The findings indicate that the innovative mixture demonstrates substantial advantages, such as a 23% re-duction in Global Warming Potential (GWP) and 58% less Water Depriva-tion Potential (WDP), highlighting its environmental and sustainable road construction benefits.
Abstract. The use of titanium dioxide (TiO2) nanoparticles on asphalt pavements as surface coating has been the subject of study since these coatings can degrade air pollutants through a photocatalytic process. However, the environmental impacts associated with the functionalization of nanoparticles on the pavement are still unknown. Therefore, this research aims to perform a Life Cycle Assessment (LCA) of an asphalt pavement with photocatalytic properties by spraying TiO2 solution over its surface. For this purpose, a comparative cradle-to-gate analysis was performed on a 1 km section of conventional asphalt pavement and a pavement functionalized with TiO2 nanoparticles. The results suggest that functionalization leads to a 17% increase in climate change, ranging from 27% to 28% in eutrophication, from 38% to 43% in the depletion of abiotic resources associated with minerals and metals, and in water consumption.
Abstract: In order to reduce costs and time associated with road quality assessment, a Pavement Management System (PMS) must embrace survey methods that expedite processes and minimize the demand for expensive procedures. With the widespread use of smartphones, numerous studies leverage these tools to simplify measurement processes. Additionally, the integration of computer vision (CV) with machine learning and artificial intelligence (AI) techniques has enabled accurate detection of pavement defects, providing foundation for road maintenance planning with less resources. This article develops and evaluates the accuracy of an alternative Continuous Visual Survey (CVS) process using a smartphone mounted on a vehicle's windshield, coupled with AI tools for detecting cracks, patches, and potholes on road pavements. An Android application was developed for smartphones to capture photos while simultaneously collecting time and GPS data. The collected data were split into two groups, with the first group used for training Convolutional Neural Network (CNN) models and the second for testing. The developed model showed an average precision of 0.72, recall of 0.50, and a mAP (Medium Average Precision) of 0.54 in detecting defects on the pavement. indicating the potential effectiveness of AI in accurately computing road distresses.
Abstract. This study explores the efficient identification of geogrids in road pavements through ground-penetrating radar (GPR) and comprehensive laboratory experiments. Geogrids are crucial in enhancing pavement strength and durability, making their effective detection vital for mainte-nance and longevity. GPR, based on electromagnetic principles, offers a non-destructive and insightful method for evaluating pavement infrastruc-ture. The literature review underscores the gap in studies specifically ad-dressing geogrid detection using GPR in road pavements, motivating the current research. To fill this void, laboratory experiments were conducted, incorporating fiberglass geogrid into asphalt mixtures. The detailed meth-odology outlines the preparation, execution, and data acquisition using GPR, emphasizing careful consideration of antenna polarities. Results high-light the visual identification of geogrids using specific treatments on ra-dargrams, demonstrating the effectiveness of GPR in detecting nuances not readily discernible in untreated images. Graphical representations bridge re-al-world geogrid depictions with radargram simulations, enhancing inter-pretability. The discussion interprets results, emphasizing the influence of geogrid type and GPR antenna position on detection accuracy. Fiberglass geogrid interference prompts considerations for dielectric properties, crucial for optimizing GPR configurations. Practical implications suggest ad-vantages in detecting specific geogrid types. In conclusion, this study con-tributes nuanced insights to geogrid detection methodologies, guiding ad-vancements in non-destructive testing for road pavements. The knowledge gained catalyzes innovation in geogrid applications and detection tech-niques, fostering improved infrastructure management practices.
Abstract. The work presents the setup of a full-scale trial site to summa-rize a case study realised within the University of Palermo. A full-scale area has been designed and constructed to test, on a large scale, a pave-ment structure equipped with sensors for continuous and in real-time monitoring and of various, crucial parameters, i.e., deformation, tempera-ture, and pressure, which are essential for road maintenance. This is par-ticularly important when non-conventional materials are used, such as recycled materials in the bituminous layers and no long-term data are available, with regards to their in-situ performance. The goal of this re-search is to act as a proof of concept for a future proof type of sensor-equipped infrastructure to monitor the performance of the pavement, for collecting data useful for pavement distress prediction.
Abstract. The International Civil Aviation Organization (ICAO) recently developed the ACR-PCR method for reporting the bearing capacity of airport pavements. From November 2024 all paved runways, taxiways, and aprons will have to be assed according to the new ACR-PCR method. The ACR-PCR will replace the ACN-PCN method, that has been worldwide used over the last four decades and is a critical information not only for Airport Operations but also for Airport Pavement Management Systems (APMS). Unlike the ACN-PCN, the ACR-PCR method takes into account mechanistic approaches, such as multi-layered linear elastic analysis (LEA) which provides a more accurate evaluation of the bearing capacity of airport pavements. The improvements achieved through the implementation of the ACR-PCR method will benefit APMS and support more sustainable management policies. This paper intends to present recent case studies for which ACR-PCR analysis has been performed, highlighting the challenges along the process. It also intends to address troubleshooting in the calculation process through FAARFIELD (the recommended calculation software developed by the Federal Aviation Administration), regarding the PCR calculation for existing, rather than new pavement infrastructure. In doing so, this paper contributes to the discussion on the relevance of providing common ground for worldwide airport management teams that will have soon to comply with the same procedures for evaluating pavement strength.
Abstract. In the present study, the effects of adding crumb rubber modifier from end of life tires on the mechanical, functional, acoustical and environmental properties of asphalt mixtures were investigated in situ. Four different dense mixtures, characterized by similar gradation curve and optimally designed in laboratory using the volumetric method, were laid on a real test field in Tuscany. In particular, a traditional hot mix asphalt mixture was chosen as a reference material to study the effect of the crumb rubber’s addition; and three experimental mixtures were produced. One hot mix asphalt with optimized texture and polymer modified binder; and two recycled tire rubber modified asphalt mixtures using the dry and wet process and the warm mix asphalt technology were investigated. The test sections were monitored to check the functional properties by using a laser profilometer to evaluate the macrotexture characteristics, and a Skiddometer to evaluate the friction. The Close Proximity method was used to evaluating the acoustic properties, and specific environmental and biological measurements were performed to evaluate the exposure levels of the workers. The results showed higher macrotexture and friction values for the mixture containing crumb rubber modifier compared to the reference mixtures. Regarding the acoustical measurements, the mixtures containing crumb rubber present better acoustical performances with 1dB(A) breakdown than the reference mixtures. For the environmental measurements, the crumb rubber mixtures present always greater values of PAHs but the overall exposure levels were similar to traditional asphalt mixtures.
The world today is experiencing a rapid emergence of intelligent vehicle technology, including active safety systems, higher degree of connectedness, and autonomous capabilities of vehicles. It is transforming the way vehicles drive and navigate the roads. There has not been any major initiative in the road and pavement engineering sector to match the fast-pace changes that have taken place. This presentation highlights the areas in the sector where changes are needed.
Over the last few decades, asphalt technology has undergone remarkable transformations. From environmentally friendly delivery methods to modifying binders and refining mix design approaches, the industry is evolving toward performance specifications. In this discussion, we explore emerging trends, emphasizing performance, sustainability, innovative additives, and portable non-destructive testing during construction and pavement laydown. These groundbreaking processes propel us toward safer, eco-friendly, and more durable road networks.
Abstract. To promote the circular economy and the sustainable pavement construction, the feasibility of using three industrial wastes for the manu-facture of warm mix asphalt (WMA) has been analyzed. The first WMA used 5% of industrial waste rich in lignin biopolymer from the wood hard-board as a bitumen partial substitute. In the second WMA, 50% of natural filler was replaced by waste biomass fly ashes from the paper industry. The third WMA substituted the 100% natural filler with waste ground granulat-ed blast furnace slag from the steel production. Additionally, a control WMA was studied. The peak load and the strain-at-failure have been ana-lyzed based on the results from indirect tensile strength (ITS) tests. The peak load was used as the main parameter to study the WMA’s brittleness. The WMA produced with 100% ground granulated blast furnace slag exhib-ited superior performance in terms of brittleness than the control mixture due to a higher breaking displacement, leading to a better cracking perfor-mance.
Abstract. Re-refined engine oil bottom (REOB) is a non-distillable residuum of waste engine oil that has been used as a softening agent for asphalt binders since the 1980s. While some researchers believe in the positive effect of REOB on pavement performance, many state agencies are concerned with the potential detrimental effect of REOB. Thus, a clear understanding of the effects of REOB on the rheological properties of asphalt binder is necessary. This study blended a REOB from a single source with an unmodified PG 64-22 binder at various REOB contents (0%, 3%, 6%, 9%, and 12%). An X-ray Fluorescence (XRF) test was used to measure the metallic component contents in the blended binders. The blended binders were also tested to evaluate the rheological properties using the dynamic shear rheometer (DSR) and bending beam rheometer (BBR). The results showed that adding REOB reduced the stiffness of the blended binders at both high and low temperatures, indicating that REOB can be used as a softener. Considering the small fraction of metallic wastes (i.e., 0.67%) detected by XRF in the REOB used in this study, the softening effect of the REOB on asphalt binder was solely due to the oil (99.33%) present in the REOB.
Abstract. The current study aims to evaluate the fatigue performance of bitumen modified with low-density polyethylene (LDPE) from various sources. To achieve this, viscosity-graded (VG 30) base bitumen was modified with 3% waste plastic by volume of bitumen. The experimental program included a linear amplitude sweep test (LAS) at 15℃. The modified bitumen exhibited higher stiffness and improved fatigue resistance. The fatigue performance of bitumen at intermediate temperatures was significantly affected by the variation of sources of plastics. Among the different sources of LDPE, bitumen modified with LDPE from source 4 exhibited the highest fatigue life. While previous studies have attributed the improvement in fatigue life to the higher degree of crystallinity of polymers, this study observed that the melt flow index (MFI) also plays a crucial role in addition to the degree of crystallinity. However, it remains unknown which parameter is more dominant. Furthermore, bitumen modified with plastics having a higher degree of crystallinity presented lesser ductile failure. Overall, the modified bitumen demonstrated better performance at intermediate service temperatures.
Abstract. A contribution for solving the depletion problem of natural resources and, simultaneously, the abundance of urban and industrial wastes, could be its application in pavement construction. For this purpose, a laboratory study is carried out in which Non-Selected Construction and Demolition Waste (NS CDW) and polypropylene (PP) plastic waste are incorporated in hot bituminous mixtures as potential replacements, respectively, for natural aggregates and bitumen. Four AC20 50/70 mixtures were put to test: a control mixture exclusively with natural aggregate; a mixture in which 10% of the mass of natural aggregate is replaced by NS CDW; a mixture in which 6% of the mass of bitumen is replaced by PP waste and a mixture in which are combined the replacement of 10% of the mass of natural aggregate by NS CDW and 6% of the mass of bitumen is replaced by PP waste. Results show that: i. a slight decrease in the Marshall stability and rise in the Optimal Bitumen Content in the mixture with 10% of NS CDW compared to the Control mixture; ii. adding PP to the mixture containing NS CDW retrieves the result for the optimum binder content obtained for the Control mixture. Both wastes diminish mixtures´ resistance to moisture.
Abstract. In recent years, the use of recycled plastics in road pavements has gained momentum as another possible solution to reduce global plastic waste as we move towards an increasingly circular economy. In Portugal, studies on the use of recycled plastics in asphalt mixtures have been underway since 2011, reinforced by the United Nations Sustainable Development Goals in 2015, the Chinese ban on the acceptance of plastic waste in 2017 and the European Commission's new Circular Economy Action Plan 2020, in which plastics are one of the most important sectors. Despite this research, only in 2023, recycled plastics were used in the national road network, for the first time.
In order to contribute to the further discussion on the use of recycled plastics in Portugal, this paper aims to provide a global overview of plastics as a raw material for use on asphalt mixtures, the research and road applications carried out to date on this topic in Portugal, as well as the main conclusions and future research opportunities. Recycled plastics offer many opportunities, but also many challenges that need to be addressed to ensure environmental sustainability and maximize their potential benefits for pavements construction and rehabilitation.
Abstract. In Singapore, about 1 million tonnes of plastic waste was generated in 2022. It was the largest amount of waste disposed in landfill with only 6% of the plastic waste was recycled. To increase the plastic recycling rate in Singapore, a study was carried out to investigate the use of recycled plastic waste in stone mastic asphalt (SMA) which is commonly used for heavy traffic applications. Previous studies have demonstrated that the recycled low density polyethylene (LDPE) plastic waste can enhance the performance of dense-graded asphalt mixture. This further study aims to evaluate the use of the recycled LDPE in SMA, and thereby expand the use of plastic wastes for road construction applications. Asphalt test samples containing various proportions of recycled LDPE plastic waste were prepared in the laboratory. The results were compared with control samples using conventional Pen 60/70 bitumen. The performance properties were evaluated with respect to different engineering properties including resilient modulus, indirect tensile strength, cracking resistance test and Hamburg wheel-tracking tests.
Abstract: The use of gecomposite incorporating multiaxial geogrid and non-woven fabric of high bitumen retention in asphalt overlays results in the increase of life of the designed pavement structure. Such an approach can offer an opportunity to increase the fatigue life (higher traffic capacity) without the need to increase asphalt overlay thickness or to reduce the thickness of asphalt overlay without reduction of pavement life eventually. This concept results in both economic and environmental benefits. This paper presents the laboratory testing results of the fatigue life of double-layered asphalt specimens with geocomposite used directly in the pavement structure fatigue life calculations. Fatigue testing was performed in the scheme of four-point bending tests (4PB) of large beams in the controlled strain mode - both for reinforced and control specimens. Based on the results obtained, one can conclude that the rated multiaxial geocomposite has a clear and positive effect on asphalt overlay performance and thus has an evident potential to extend the asphalt pavement fatigue life. This paper also presents a slightly modified concept of the Mechanistic-Empirical pavement design method based on fatigue improving factors derived from the laboratory test investigation, allowing reinforcement benefits to be implemented into the design process. Finally, an example of the calculation of reconstructed asphalt pavement with the enhancement of the asphalt overlay reinforced by geocomposite is also presented.
Abstract. Preserving the road surface and maintaining it at a proper functional level is essential to safe transportation. Several alternatives exist to serve this need and to deliver effective pavement surface preservation. Among these alternatives, high performance thin asphalt overlays have been utilized and promoted by several states in the United States. Under the research presented here, performance of thin asphalt overlays was evaluated through placement of three pilot projects. Advanced technologies such as thermal imaging and ground-penetrating radar were utilized to determine the uniformity of such mixes during placement in regard to temperature and density. Field evaluations, in general, indicated improved performance of these roads with respect to skid resistance and ride quality. Field measurements have indicated minimal rutting, fatigue cracking, and raveling at all three sites after years in service. Reflective cracking has been the dominant distress at all three projects. Overall, it can be assessed that both construction and performance of the three pilot projects has been successful.
Abstract. Geosynthetic materials have been utilized in various engineering applications. In pavement engineering, geosynthetics can serve as an interlayer system, providing reinforcement, filtration, and drainage, etc. Three field trial sections were constructed, including one section with conventional pavement structure, one section with fibreglass geogrid in the asphalt binder course, and one section with geogrid composite on top of the subgrade. Laboratory testing was conducted on sampled unbound materials to evaluate the subgrade condition for further evaluation of the impact of geosynthetics. Field testing was also conducted on each layer of pavement structure during construction. The section with geogrid in the asphalt layer has the highest stiffness tested on the asphalt binder course resulting from the geogrid-reinforcement. Long-term monitoring is needed to further evaluate the function of geogrid composite on the subgrade.
Abstract: At a time when the construction of new roads is increasingly taking a back seat to their preservation, the question of how to deal with maintenance measures, such as the reinforcement of pavements with asphalt reinforcements, is becoming more and more important. This applies in particular to the possible modelling of such asphalt reinforcements for dimensioning purposes. For the dimensioning of asphalt reinforcement grids, the estimation of their service life or the extension of the service life compared to a reference pavement without reinforcement is of particular importance. This paper shows how the service life of reinforced pavements can be estimated in the laboratory with the aid of accelerated traffic loading.
Abstract. Exploring the reflective crack resistance of geosynthetic-reinforced asphalt concrete (AC) is the core focus of this paper, addressing a vital aspect of pavement longevity under fatigue loading. Reflective cracking, primarily induced by traffic and thermal loads, is a predominant failure mechanism in pavements. The current study quantifies the crack resistance capacity of geosynthetic-reinforced AC using a modified four-point beam fatigue test, namely the Notched Beam Fatigue Test (NBFT). This method evaluates the endurance of reinforced AC to repeated load cycles before failure, providing a tangible measure of crack resistance. The failure criterion in laboratory asphalt fatigue testing is pivotal; the methodology focuses on simple measurements such as load and displacement, deliberately avoiding reliance on visual crack observation and advanced techniques like Digital Image Correlation (DIC). Nevertheless, correlating traditional failure criteria with DIC results is integral to the study, aiming to enhance the predictability of field performance and assist in paving design decisions. A comprehensive explanation of the reflective cracking mechanism, including the implications of different failure modes during testing, is provided. This research contributes to understanding geosynthetic-reinforced AC behavior under real-world loading conditions, offering valuable insights for pavement design and maintenance strategies.
Abstract. As part of ongoing research study two different methodologies of stiffness determination have been compared. Stiffness tests on a selection of Asphalt Concrete mixtures (AC) containing various contents of reclaimed asphalt have been performed using the indirect tensile test on cylindrical specimen with pulse load form (IT-CY) and 4-point bending test with prismatic specimens (4PB-PR). The determining aim presented by this paper was to compare interdependency of resulting stiffness values from both test methods. The above-mentioned test methodologies are commonly used for many years. A total of 56 mixtures was manufactured and tested. The evaluated samples covered asphalt mixtures containing varying content of reclaimed asphalt as are used in the Czech Republic in all pavement layers. The group was further divided according to used bituminous binder (non-modified vs. modified) and reclaimed asphalt content.
Abstract. This paper presents the properties of hot- and warm-mix asphalt concrete and possible use in pavements using a high rate of RAP (reclaimed asphalt pavement) and waste cooking oil (WCO). Laboratory experiments delivered results on the mixtures' essential volumetric and Marshall charac-teristics and their several mechanical performance parameters. These out-comes are used to deliver a mix-design procedure and propose critical rec-ommendations on using that type of asphalt concrete. The paper provides pavement structures for medium/low-traffic roads with hot- or warm-mix asphalt concrete layers with up to 80% of RAP and WCO as a rejuvenator. The paper also includes a direct cost analysis to show the savings achieva-ble with that technology. The results allow us to conclude that the hot- and warm-mix asphalt concrete materials developed in the project are suitable, durable after ageing and cost-effective for medium/low-traffic road pave-ments.
Abstract. Annually, approximately 120 million tons of asphalt pavement are milled, resulting in the generation of Reclaimed Asphalt Pavement (RAP). Despite its advantages, fully maximizing RAP usage poses challenges, particularly as RAP content exceeds 20%, leading to a reduction in pavement resistance to cracking. The aging of asphalt binder, which causes increased stiffness and susceptibility to cracking, is a primary contributing factor. Engineers addressing high RAP content must select a softer virgin binder or incorporate a recycling additive into mix designs. Bio-oil additives, derived from plant or animal sources, are known for their ability to modify asphalt binders, enhancing rheological characteristics, temperature susceptibility, and aging resistance. This study focuses on assessing the effectiveness of a bio-oil additive in producing asphalt mixtures with significant RAP proportions, with an emphasis on fracture behavior. Two reference mixtures were examined: one without RAP and one with 20% RAP without a recycling agent. Additionally, two mixtures with RAP contents of 40% and 70% were prepared and tested, incorporating a measured quantity of bio-oil additive to rejuvenate the RAP-aged asphalt binder. Superpave Indirect Tensile (IDT) testing procedures were employed to comprehensively investigate the influences of RAP and the bio-oil additive on fracture behavior. Rheological investigations, specifically Multiple Stress Creep Recovery (MSCR), ensured that the additive's presence did not compromise the blend's response to high temperatures. The results demonstrate the effectiveness of the bio-oil additive in reactivating aged bitumen in RAP, maintaining comparable fracture behavior to the reference mixture while preserving resistance to permanent deformations at elevated temperatures. Careful consideration of additive dosage is emphasized for optimal performance.
Abstract. Reclaimed asphalt pavement (RAP) materials constitute aged binders that warrant recycling to achieve the required rheological proper-ties. For this purpose, recycling agents are added to the RAP materials to ‘soften’ the aged binder and meet the target rheological response. The rheo-logical response of the recycled binders, particularly their sensitivity to temperature changes, predominantly contributes to pavement distress, such as permanent deformation and fatigue cracking. Therefore, it is necessary to quantify the variation in the rheological response of the recycled binders over a wide range of temperatures. Also, limited studies are available on the temperature sensitivity of recycled binders, especially concerning various ages of RAP binders. To address this, an unmodified binder was aged in a forced draft oven for 24 and 86 hours to simulate two extents of aging. Re-cycling agents were added to the aged binders, and the binders were subject-ed to time sweep tests at temperatures ranging from 10 to 70 °C. The Arrhe-nius plots of absolute shear viscosity and energy dissipation were used to calculate the activation energy, which is used as a measure of the tempera-ture sensitivity of the binders. Results indicate that temperature sensitivity is greatly influenced by aging and the addition of recycling agents. Among the recycled binders with identical high-temperature performance grades, the recycled binder containing 86 hours of oven aged binder exhibited low-er temperature sensitivity. Notably, these differences in rheological re-sponses between the recycled binders were most prominent at lower test temperatures of 10 to 30 °C.
Abstract. Polymer-modified bitumen performs better at different tempera-tures and loading conditions than pure bitumen. Therefore, using this type of bitumen in recycled asphalt mixtures containing reclaimed asphalt (RA) material can lead to a better performance than pure bitumen. However, the presence of a very hard and aged binder in the RA, especially for high RA incorporation ratios, may increase bitumen stiffness and negatively affect the performance of the polymer-modified bitumen. Therefore, it is essential to know the effect of recovered binders on the characteristics of polymer-modified bitumen. This study investigated the characteristics of an elasto-meric polymer-modified bitumen combined with 30% recovered bitumen and a rejuvenating agent using penetration grade, softening point, viscosity, and elastic recovery tests. By analysing the master curves obtained from dynamic shear rheometer (DSR) tests in a wide range of temperatures and loading frequencies, the rheological characteristics of the same bitumen were also evaluated and compared to commercial bitumen samples (i.e., polymer-modified bitumen and pure 70/100 pen grade bitumen). The con-ventional test results showed that the recovered bitumen from RA increases the stiffness of polymer-modified bitumen even with a rejuvenator. How-ever, the DSR test results showed that it is possible to maintain the rheo-logical characteristics of polymer-modified bitumen combined with 30% recovered binder and a rejuvenator.