A multiscale-multiphysical model framework for strength development analysis of LC3 concrete

Abstract The emerging limestone calcined clay cement (LC 3 ) has opened new sustainable pathways. The synergy among cement, limestone, and calcined kaolinitic clay during hydration causes pore size refinement, leading to desirable mechanical capacity despite reduced cement usage. Nevertheless, due to lack of systematic method and data, there is a knowledge gap in quantifying the correlation between strength growth at macroscale and evolving LC 3 binder chemistry, which would often require a multiscale-multiphysical approach. To address this, a numerical framework, integrating kinetic-thermodynamic hydration model with multiscale homogenisation and phase field to quasi-brittle fracture model for mechanical analysis, is developed. Surrogate relations to describe pore connectivity and critical fracture energy as functions of time-dependent hydration characteristics are also established. Through fracture modelling, the proposed method is carefully verified against the reported experiments for compressive strength predictions of LC 3 concretes (up to 65 MPa of 28-day strength) prepared with diverse cement replacement rates (10–50%) and calcined kaolinitic clays of wide-range metakaolin contents (18–95%). Further numerical explorations demonstrate that the notable effects of metakaolin content and limestone fineness on compressive strength developments can be quantified using the proposed method, providing a useful tool for strength-based analysis and design of LC 3 concrete.