Multi-scale Modeling And Application Of Concrete Considering The Cement Hydration Process

The mechanical properties of dam concrete cast in real environments are affected by factors such as wind speed,relative humidity,and temperature.Therefore,obtaining the true performance of concrete is of great significance for ensuring the safety of dams.Microscopic composition,structure,and mechanical properties are key factors affecting the macroscopic mechanical properties of concrete,while the microscopic structure and mechanical properties are controlled by the cement hydration process.Existing research has not fully considered the impact of the cement hydration process on the mechanical properties of cement paste at the microscale and the true ma croscopic performance of concrete in real environments.In this study,we conducted research on multiscale modeling of concrete considering the cement hydration process and its applications through theoretical research,numerical simulations,and experimental testing.The main research contents of this paper are as follows:(1)In view of the large differences in simulation results of the mechanical properties of cement paste at the microscale and the lack of consideration of the influence of cement hydration process,this study first proposed the “centripetal displacement method” for high proportion particle placement and the “extreme contact positioning method” for particle contact judgment,establishing an efficient and accurate cement hydration model.Th en,using the cohesion force model,the mechanical properties of cement paste at the microscale were simulated and verified.Finally,combining the hydration model with the cohesion force model,a simulation method for the mechanical properties of cement p aste at the microscale considering hydration was proposed,obtaining the mechanical properties of cement paste during different hydration processes and revealing the influence mechanism of hydration process on the microstructure and mechanical properties of cement paste.(2)In view of the limitations of traditional multiscale models only considering spatial multiscale,based on the mechanical properties of cement paste at the microscale,and combining the cement hydration model with multiscale features of concrete,this study established a multiscale model of cement paste-mortar-concrete full-age mechanical properties considering cement hydration.Multiscale simulations of the full-age mechanical properties of mortar and concrete were carried out,establishing the relationship between the mechanical properties of cement paste,mortar,and concrete,and achieving accurate prediction of the full-age mechanical properties of cement-based materials.(3)In view of the difficulties in obtaining the true performan ce of dam concrete under real environments,this study first conducted macro and micro experimental tests under different environmental conditions and optimized the cement hydration model based on the test results.Then,using the optimized space-time multiscale model of concrete,a simulation framework for the true performance of dam concrete considering the real environment’s impact on cement hydration was constructed.The true performance of dam concrete under real environments was simulated,revealing t he evolution mechanism of the true performance of dam concrete,which is of great significance for controlling the quality of dam concrete under real environments.