EFFECT OF SIMULTANEOUS ADDITION OF GYPSUM AND CALCIUM NITRITE ON HYDRATION REACTION OF LOW-BASICITY SLAG

Abstract

This study investigated the effect of the simultaneous addition of gypsum （CS） and calcium nitrite （CN） on hydration reaction and strength development of low-basicity （about 1.6） CaO-MgO-Al₂O₃-SiO₂ glass and blast furnace slag. When CN and CS were added to the low-basicity slag, the solubility of Al from the slag increased by CN addition and the amount of Ettringite （Et） increased significantly by the reaction between CS and dissolved Al. As a result, the heat liberation of hydration and the combined water of the low-basicity slag with CN and CS increased to those of the high basicity slag with CS. However, as the excess formation of Et reduces the long-term strength, the amount of gypsum should be minimized when CN is added to slag.