Effect of citrate retarders on the expansion property and hydration behavior of light-burned magnesia cement-based materials

Abstract

This paper investigated the effect of citric acid (CA), magnesium citrate (CM), and lithium citrate (CL) on the expansion property and hydration behavior of light-burned magnesia (LBM) cement-based materials. Setting time, linear expansion, hydration kinetics, thermogravimetric analysis, XRD and SEM were used to characterize the expansion and hydration performance of LBM cement-based materials. The results showed that the retarding effect of citrates retarders was closely related to the citric ion concentration with a minimal influence of cation on the setting time. The expansion of LBM cement-based materials was inhibited by CA, but promoted by CM and CL. Through linear and power function fitting, the method of coordinated regulation of setting time and expansion rate of LBM cement-based material was obtained. Both hydrogen ion and citric acid ion inhibited the hydration heat exothermic. Agglomeration, dissolution and precipitation of LBM crystal were observed in the ultra-early hydration process. In LBM cement-based materials, CA and CM inhibited the formation of Ca(OH)2, which was not influenced by CL.