The effects of surface parameters and curing conditions on the bond strength of alkali-activated repair mortar with optimal levels of ground granulated blast-furnace slag and micro-silica

The effects of surface parameters and curing conditions on the bond strength of alkali-activated repair mortar (AARM), optimised with ground granulated blast-furnace slag (GGBFS) and micro-silica (MS), were investigated. The research was divided into two main parts: (a) the optimisation of AARM using various levels of GGBFS and MS and (b) evaluation of factors influencing the adhesive strength of the optimised AARM. GGBFS was used as the base material in quantities of 400, 500 and 600 kg/m³, while MS was added at 5%, 10% and 15% by weight of the GGBFS. Sodium silicate and sodium hydroxide were used as alkaline activators. Surface preparation involved milling and brushing with a wire brush, followed by curing the samples under three different conditions: open air, immersion in water at 24°C and steam curing without direct contact with water at a temperature of 90°C. Adhesion resistance tests were then conducted. The results indicate that the incorporation of 5% MS in a slag-based mortar with a density of 600 kg/m³ led to initial and final setting times of 18 min and 31 min, and yielded optimal mechanical properties and durability. Additionally, surface preparation using milling (grooving) and cold water curing significantly enhanced the adhesion resistance.