Pozzolanic reaction of lightweight fine aggregate and its influence on the hydration of cement

Although lightweight fine aggregate (LWFA) has been used as an internal curing material in concrete for several decades, its chemical activity is not well estimated. In this research, LWFA is incorporated into cement paste to investigate the pozzolanic reaction and its influence on the hydration of cement. The results show that LWFA is more chemically active under heat-cured conditions and continuously releases Al and Si, which increases the Al/Ca and Si/Ca ratios of hydration products. Moreover, LWFA provides large surface for nucleation and the growth of hydration products and promotes the formation of C-A-S-H. The microstructural characterization demonstrates that the reaction products of LWFA are very similar to those of metakaolinite by-products and kaolinite-based clay waste.