Early-age hydration characteristics and kinetics model of blended cement containing waste clay brick and slag

Low-carbon blended cement was prepared by mixing Portland cement, clay brick powder (CBP) and slag. The early-age hydration mechanism was studied by analyzing the hydration characteristics and kinetics parameters of blended cement with different admixture replacement rate, CBP to slag ratio and temperature. The results indicate that increasing admixture replacement rate accelerates cement hydration and leads to the displacement of exothermic peaks. However, the reduced C3S content in blended cement reduces the peak intensity and reaction rates of NG-ID (nucleation and crystal growth -phase boundary reaction -diffusion) processes. Slag promotes the nucleation and growth of C-S-H gel slightly more than CBP before the third exothermic peak. Then, the slag reaction in the deceleration period consumes a lot of sulfate ions, resulting in the high third exothermic peak. High temperature provides nucleation driving force to accelerate the cement dissolution and ions migration, thus, the reaction rates of NG-I-D processes are increased as the temperature rises.