Effect of using grounded coral sand on hydration and strength development of portland cement paste: Experimental and GEMS modelling investigation

Abstract

The use of coral sand is mainly focusing on how to use it as aggregate in marine areas, much fewer studies have been conducted to investigate its usage as SCM (supplementary cementitious material) after being grounded into powder. In this context, the influence of CSP(coral sand powder), used as SCM, on the hydration and strength development of Portland cement paste was investigated. In order to describe the hydration process, Experiments including Isothermal calorimetry, XRD and TG analysis were used, along with the GEMS modelling system. The effect of CSP content, curing temperature and w/c were investigated in this study. The result shows that coral powder plays a nucleus effect in the process of cement hydration, which promotes the early age hydration of cement. Low coral powder substitution rate of no more than 10% can enhance the strength development of CSP concrete. However, with the increase of age and replacement rate, the coral powder shows a dilution effect which would slower the exothermic rate of the cement system. As to the hydraulic products. The results shows that the form of aluminum-containing hydration products in the coral powder-cement-based system is closely related to the content of coral powder. Apart from these, the increase of the w/c ratio is conducive to increase the hydration rate and hydration product content of coral powder-Portland cement systems. And with the increase of hydration temperature, the hydration rate of the cement system and the generation rate of hydration products are accelerated, although the main type of hydration product is not changed.