Study of the effects of fine coral powder and salinity on the mechanical behaviour of coral sand-seawater cement mortar

Abstract

The coral sand and seawater are widely used as construction materials. The coral powder and salt contained in the coral sand-seawater cement mortar have a significant effect on the void distribution, cemented effect and mechanical behaviours. Thus, the mechanisms for the influences of coral powder content and salinity were investigated by a series of piezoelectric transducer (PZT) tests and uniaxial compressive strength tests. The cement mortar specimens with various coral powder contents and salinities were prepared and examined. The microstructure and pore characteristics of mortar under different conditions were analysed by scanning electron micrograph (SEM). The results show that the main ingredient in coral powder (i.e., CaCO3) would accelerates the cement hydration. The fine particles could fill the skeletal pores. Therefore, an appropriate content of coral powder can improve the strength and deformation properties of mortar. Salt had the dual effect of decreasing the stiffness of the cemented mortar specimen and intensifying the aggregation of coral powder particles. The aggregation of the coral powder particle in coarse skeleton is the key factor affecting the overall mechanical properties of the seawater-sea sand cement mortars. The coupling effects of coral powder and salt influence the microstructure and macroscopic mechanical properties of the mortar, and the effects of the two factors are mutually restricted. These research results provide a reference for guiding the optimisation of the mechanical properties of coral sand-seawater cement mortars and improving the safety and stability of structures engineered with these mortars.