Speaker
Description
3D concrete printing (3DCP) aims to revolutionize construction by increasing automation, reducing material usage, and enabling customized designs. Despite its potential, the lack of regulations and reliance on trial-and-error methods result in significant waste and inefficiencies. Reliable models are needed to predict and control the complex printing process with its various influencing factors from material, process, and environment.
This study aims to develop a structural model to predict print stability and prevent buckling and material failure in extrusion-based 3D concrete printing (3DCP), with a focus on environmental influences, particularly temperature. The structural build-up of the material is crucial for stability but is influenced by material ingredients, water-binder ratio, and ambient conditions, which vary in real-world projects. It describes the process of cementitious material gaining strength and stability during its early ages due to thixotropy and early hydration. Modeling that, a time- and temperature-dependent model for the evolution of early-age material parameters, such as stiffness, is derived. The model employs the maturity method, using an equivalent time to capture the temperature influence. It is verified using experimental data on stiffness evolution from squeeze flow tests and yield stress evolution measured from rotational rheometer tests. The model parameters are estimated using Bayesian inference, and validation shows good agreement with experimental data for both parameters at the material level. Subsequently, the derived time- and temperature-dependent stiffness model is adapted into a structural simulation using an elastoplastic material law with nonlinear hardening to study the temperature effect on the stability of 3DCP. Layers are activated sequentially based on a pseudo-density approach. The method is illustrated with an example of a printed wall with a width of one layer under varying ambient temperatures. The temperature impact on buckling and material failure during printing is demonstrated and numerically investigated through a sensitivity study.
