Correlating strength development with hydration characteristics for multi-blend fly ash concrete

Compressive behaviour is a quintessential property of concrete, governed by material fracture resistance and related to binder type, mixture, and age. Though experimental and data-driven methods have been widely exploited for strength analysis, the limitation is in scientifically correlating mechanical property to cement chemistry. In this study, taking multi-blend fly ash concrete as precursor, a multiphysics coupling method is developed to address the identified gap. The proposed method features a kinetics-thermodynamics model for hydration analysis and multiscale homogenisation for elasticity assessment. A unified phase field solution to combined brittle to quasi-brittle fracture is also derived for stress-strain relation analyses. Through systematic model examinations, a model defining the critical fracture energy as a time-dependent function of evolving mortar elasticity and C-S-H content is proposed. With rigorous verifications, the proposed method is demonstrated to be applicable to both binary and ternary concretes with up to 80% cement replacement using a combination of fly ash and hydrated lime. Furthermore, it is capable of dissecting the influences of binder mix and progressive hydration on concrete strength developments to 90 days of age with a cubic strength up to around 100 MPa. • Concrete strength development is linked to hydration through multiphysics coupling • Unified phase field solution to brittle and quasi-brittle fracture is derived • Strength analysis by fracture modelling at mesoscale concrete level is performed • Correlation between fracture toughness and hydration characteristics is quantified • Robust strength predictions for binary and ternary fly ash concretes are achieved