Improvement of durability and drying shrinkage of sodium carbonate activated slag through the incorporation of calcium hydroxide and sodium hydroxide

Abstract

This study investigates the drying shrinkage, permeability, chloride migration and pore size distribution of sodium carbonate (NC) activated slag. To this end, the effectiveness of two different modifiers, e.g. calcium hydroxide (CH), sodium hydroxide (NH), on shrinkage and permeability of NC-activated slag were investigated. Within this context, NH was replaced with NC at 20% and 40%, while CH was replaced with slag at 3% by weight. The results showed that drying shrinkage can be mitigated with NH and CH substitution, while attaining comparable performance with the ordinary Portland cement (OPC). Moreover, chloride penetration and sorptivity was reduced with the aid of the modifiers, CH-modified mixes presented better performance than OPC-based mixes. The pore structure was refined through CH-substitution. Formation of a high amount of calcite and lower unhydrated slag particle area fraction, which was confirmed with the SEM analysis, proved the lower permeability of CH-modified mixes. (C) 2020 Elsevier Ltd. All rights reserved.