Simulation of the microstructure formation in hardening self-compacting cement paste containing limestone powder as filler via computer-based model

Abstract

With the development of concrete technology, fillers are widely used in high performance concrete to improve its properties. Among them, limestone powder is popularly added in self-compacting concrete to gain good flowability. However, by lack of experimental data, several materials properties after the addition of limestone powder are still not sure, which actually yield some uncertainty for the further use of limestone powder in cement-based materials. In this study, by employing computer-based model, the microstructure of self-compacting cement paste containing limestone as filler is simulated and further used to investigate the role of limestone in hardening materials. To gain this goal, thermometric isothermal conduction calorimetry, thermal analysis and backscattered electron image acquisition were applied to understand the hydration kinetics with the addition of limestone filler. After that, a computational materials model based on HYMOSTRUC was developed to simulate the formation of microstructure in materials containing limestone powder. The predictive ability of the model was validated with the experimental test results. Then the developed model was employed to investigate the influence of several variables, such as water to cement ratio, limestone filler content and fineness, on the microstructure formation in hardening materials. The numerical experiments show that the addition of limestone filler could result in a denser microstructure at the initial hydration stage. With the proceeding of hydration, the limestone powder has a decreasing influence on the microstructure, and could obstruct somewhat the formation of a denser microstructure at later hydration stage. And it is found that computer-based modelling is an effective method to provide insights into the material behaviour, by relieving researchers from numerous repeated experiments.