Effect of nano-CaCO₃ on hydration of cement containing supplementary cementitious materials

The efficacy of the addition of nano-CaCO₃ in accelerating the hydration of ordinary Portland cement (OPC) delayed by the presence of high volumes of supplementary cementitious materials including fly ash and slag was investigated. The conduction calorimetry indicated that the early hydration of OPC was significantly accelerated by the addition of the nano-CaCO₃ and the higher the amount of CaCO₃ addition, the greater was the accelerating effect. The thermogravimetric analysis results showed that the amounts of added CaCO₃ became slightly lower as the hydration took place; however, any new reaction products were not detected by the X-ray diffractometry analysis. The engineering properties, including microhardness and modulus of elasticity, in the early stage of the hydration were remarkably improved by the addition of nano-CaCO₃. It was suggested that the seeding effect of the nano-CaCO₃ particles and the nucleation of C–S–H caused the enhanced strength development.