Influence of modified quartz tailing on strength and autogenous shrinkage of cement pastes

The amount of quartz tailing applied in concrete construction is limited due to the low performances of cementitious materials containing quartz tailing. The aim of this study was to mitigate the autogenous shrinkage and improve the strength of blended cement containing quartz tailing by modifying the interface between the quartz tailing and the cement matrix. In this study, the quartz tailing was modified by calcining the material mixed with carbide slag at 1050°C. The compressive strength, autogenous shrinkage, microstructure and nanomechanical properties of the blended cement pastes containing modified quartz tailing were investigated. The results show that modified quartz tailing particles mainly consist of an inner core of quartz and a β-dicalcium silicate (C₂S) layer. Compared to unmodified quartz tailing, modified quartz tailing increases the compressive strength of the blended cement paste and at the same time decreases its autogenous shrinkage. In addition, the nanoindentation modulus and hardness of the interfacial zone between quartz tailing and cement matrix are improved, and the porosity of the blended cement paste is decreased. This can be attributed to the formation of calcium silicate hydrate gel owing to the hydration of the β-C₂S contained in the modified quartz tailing, and hence enhancement of the interface microstructure between the quartz tailing and cement matrix.