Effect of Citric Acid on the Time-Dependent Rheological Properties of Magnesium Oxychloride Cement

Abstract

This study was intended to evaluate how citric acid influences the time-dependent rheological properties of magnesium oxychloride cement (MOC). For this purpose, rheological parameters, setting time, electrodeless resistivity, crystal phases, morphology, hydration product, and compressive strength were investigated. The results show that the addition of citric acid can improve the time-dependent rheological properties of MOC pastes due to the retarding effect of the citric acid. The citric acid dosages of .15, .25, and .35% can stabilize the rheological properties of MOC paste in 1, 2, and 3 h, respectively. The addition of citric acid prolonged the setting stage by introducing free H+ that weakened the flocculated structure of MOC paste and delayed the formation of 5MgO·MgCl2·8H2O. The early compressive strength was significantly decreased with increasing dosages of citric acid; however, the citric acid had less of a negative effect on the late compressive strength.