EFFECT OF CaO·2Al₂O₃ ON IMMOBILIZATION OF CHLORIDE ION IN PASTE WITH EARLY STRENGTH PORTLAND CEMENT AND GROUND GRANULATED BLAST-FURNACE SLAG

Abstract

 In paste with high early-strength Portland cement and ground granulated blast-furnace slag, CaO·2Al₂O₃ admixed in the paste reacts with calcium hydroxide, which is the cement hydrate, to produce hydrates such as hydrocalumite group. In this research, it is clear that the hydrocalumite group has the chemical effect to immobilizing chloride ions and the physical effect to reducing porosity of the paste to prevent penetration of chloride ions from the outside. These two effects can greatly reduced the apparent diffusion coefficient of chloride ions in the paste. The effects tends to be lower when the curing temperature in early age was 60°C, but there is little change when the paste was carbonated.