Investigation of the effect of recycled concrete additives on the properties of cement -based materials

In this paper, the aim is to explore the potential of recycled concrete powder (RCP) as an internal curing agent in reducing the shrinkage of cement -based material. Different amount of RCP was added into cement paste and the autogenous shrinkage of cement matrix was measured. Low -field nuclear magnetic resonance (NMR) was applied to monitor the water state during the hydration process. Scanning electronic microscope (SEM) was used to observe the micro -morphology of RCP added cement matrix. The results show that the autogenous shrinkage of samples with addition of RCP was remarkably reduced. This is because much water was captured by RCP and the water will be released to balance the capillary pressure of the cement matrix, thus leading to a smaller deformation. SEM images also showed that there were fewer microcracks after adding RCP. Although the shrinkage was inhibited by RCP to some extent, the compressive strength of samples with the addition of RCP decreased. Our work proves that RCP is an effective internal curing agent for cement-based material.