Evolution of early hydration in mortar by using waste dolomite powder as a micro-aggregate

Abstract

The evolution of early hydration in cement – based material is always one of important issues for investigating their engineering application. This study investigated the early hydration reaction of mortars containing different waste dolomite powder (WDP) contents. Compared to the reference sample (WDP0), the hydration process, hydration products, pore structure and mechanical properties of samples prepared by WDP were studied at the early stage. For the hydration process, the 1H low – field nuclear magnetic resonance (NMR) and chemical shrinkage testing results indicated that the process of early hydration of cement could be significantly accelerated by incorporating WDP. Meanwhile, the quantities of hydration products (Portlandite and calcite) in samples with WDP have a significant variation by X-ray diffraction results and thermogravimetric analysis. In addition, the WDP40 has denser pore structure and higher mechanical properties than WDP0. After curing 3 d, the pore volume of WDP40 has a reduction of 17.84 %, the flexural and compressive strength of WDP40 were increased by 6.6 % and 18.06 %, respectively. Based on the mechanism analysis, the filling effect and nucleation effect of WDP in mortars contributed to the improvement of early cement hydration. This study is meaningful to evaluate the impact of WDP on the evolution of early cement hydration, which is expected to offer a reliable reference for the application of inert materials in cement – based materials.