Effect of Alkaline Solution and Curing Conditions on the Strength of Alkali – Activated Slag Mortar

The aim of this work was to study the compressive strength and microstructure of alkali - activated slag mortar (AAS mortar) under different curing methods. Granulated blast furnace slag (GBFS) was activated by the combination of sodium silicate liquid (Na₂ SiO₃) and sodium hydroxide (NaOH) with a silicate modulus (a SiO₂/Na₂O weight ratio) of 1 and different Na₂ O concentrations of 4, 6, 8 % by slag weight. AAS mortar specimens were cured in the ambient condition (20 ± 5 °C, 60 ± 5 % RH) (RH: Relative humidity), in a dry oven at 80 °C, and in the saturated limewater at 80 °C for 24 hours. After curing, the specimens were kept in the ambient condition until the time of testing. Scanning electron microscopy (SEM) was used to assess the mortar microstructure. The results revealed that the Na₂ O concentration of alkaline solution and curing method significantly affected the compressive strength of AAS mortar. Curing in the saturated limewater at the high temperature was found to be effective in promoting the mortar strength at later ages.