XCT-informed coupled creep-damage FE model for time-dependent micromechanical behavior of hardened cement pastes

Abstract

This study presents an experimentally informed coupled creep–damage modelling framework for the time-dependent micromechanical behaviour of hardened cement paste. Using realistic microstructures, a viscoelastic formulation solved by an exponential algorithm, and a continuum damage model, the framework consistently captures microscale creep, creep recovery, and strain-rate-dependent response. The results show that microstructural discretization strongly affects predictions: coarse discretizations underestimate porosity and overestimate hydration, leading to overpredicted stiffness and strength. The model reproduces measured flexural strength, elastic modulus, and the observed brittle failure. Low-stress creep and recovery are predicted accurately, with high recovery ratios indicating predominantly linear creep. The calibrated HD-CSH/ LD-CSH creep modulus ratio is consistent with experimental insights, supporting that calcium hydroxide increases the creep modulus of CSH. Strain-rate effects are also captured: slower loading allows more creep and earlier damage in weaker phases, while faster loading drives damage into stronger phases, yielding higher apparent stiffness and strength with more pronounced damage patterns. Overall, the framework provides a physically consistent basis for studying microscale creep–damage interactions. Future work will incorporate temperature and moisture effects and extend the approach to multiscale simulations of long-term concrete behavior under realistic environments.