Effect of coral powder and ground-granulated blast‑furnace slag on the hydration behavior of cement paste

Coral wastes are produced during the construction of island. The use of coral wastes in concrete is beneficial to economy and environment. Coral waste as aggregate in concrete has been studied well. Now, coral powder (CP) as mineral admixture to replace cement partially in concrete is a different approach to reuse coral waste. However, the use of more CP in concrete will definitely affect the property of cement-based material. In order to improve the mechanical property and use more CP in construction, ground-granulated blast-furnace slag (GGBFS), a kind of latent hydraulic material, is considered in this study. Furthermore, the synergetic effect of CP and GGBFS on the hydration of Portland cement (PC) is seldom researched systematically. In this study, CP and GGBFS are mixed into cement in five proportions to research the hydration process of cement paste comprehensively by isothermal calorimetry test, X-ray diffraction, and thermogravimetric analysis. The properties of the GGBFS-CP-PC ternary system, such as the chemical shrinkage and compressive strength, are also determined. The results show that the existence of GGBFS will influence the secondary hydration of C₃A when the mass ratio of GGBFS to cement is above 0.25 in binder. The reaction of CP is accelerated by the active alumina phase in GGBFS. The presence of GGBFS can promote the formation of carboaluminate. During the infrastructure construction in island, it is reasonable to use CP in concrete, and the use of CP together with GGBFS can ensure the mechanical properties of concrete structures.