MgSO₄ RESISTANCE OF BLAST FURNACE SLAG CEMENT WITH ANHYDRITE AND LIME STONE POWDER, AND MATERIAL DESIGN FOR SULFATE ATTACK

Abstract

This study was conducted to investigate the mechanism of sulfate attack with MgSO₄ solution of cementitious materials containing Ordinary Portland Cement（OPC）with Blast Furnace Slag（BFS）, anhydrite（AH：CaSO₄）and lime stone powder（LSP：mostly CaCO₃）, and to design a cementitious material with improved sulfate resistance. This study also focused on the influence of adding BFS, AH and LSP on MgSO₄ resistance of OPC paste specimens. The sulfate resistance was improved by adding BFS, AH and LSP；the best MgSO₄ resistance was found for BFS/OPC ratio＝70：30 with AH 5-10％-LSP 5-20％. It was concluded that（a）the amounts of CH, responsible for both expansion and shrinkage, could be decreased with increasing the BFS replacement ratio（especially by adding 70％ BFS）（b）a large amount of ettringite instead of monosulfate was produced before immersion in sulfate solution when AH was added and（c）adding LSP resulted in production of monocarbonate, which was stable in sulfate solution, instead of unstable monosulfate.