From cement chemistry to pseudo-ductile mechanical behaviour of engineered cementitious composite: A multiphysical approach

Engineered cementitious composite made with incorporating polyvinyl alcohol fibre and fly ash has been demonstrated to strike a perfect balance among unique pseudo-ductile mechanical performance, sustainability, and cost. Nevertheless, the tensile strain-hardening behaviour of the composite is time- and case-dependent, where simply taking 28-day property as a baseline may overestimate its long-term capacity. Such an issue has yet been addressed due to lack of scientifically robust method to correlate mechanical characteristics with binder chemistry. In this regard, a physics-based approach, featuring multiphysics coupling, is developed to close the knowledge gap. Specifically, a novel phase field to ductile fracture model is adopted to numerically describe the multi-cracking enabled pseudo ductility of engineered cementitious composite. For the first time, key model parameters that govern the material mechanical behaviour are quantitatively correlated with fundamental binder chemistry, in addition to fibre characteristics, through hydration and multiscale homogenisation analyses. Following rigorous validations in two- and three-dimensional settings, the method is found applicable to composite mixes with a fly ash replacement rate of 50% – 80% (by mass) and a fibre content ranging 0.5% – 2% (by volume), capable of generating insights to support material design and structural analysis of sustainable engineered cementitious composites.