The effect of dunite powder and silica fume on the viscosity, physico-mechanical properties and sulphate resistance of self-compacting mortars

Abstract

Recently, the use of waste and novel natural resources in the concrete industry has drawn the attention of researchers from all around the world. Self-compacting mortars (SCMs) can be created using dunite powder (DP) as natural cementitious material and silica fume (SF), and provide the distinctive fresh properties required for SCMs. This study analyzes the viscosity, mechanical characteristics, and sulphate resistance of SCMs containing SF and DP. Twelve different combinations, containing reference, binary, and ternary mixtures, were created by partially substituting Portland cement (PC) with DP and SF. Binary mixes were produced by substituting cement with DP at weight replacement rates of 5, 10, 15, 20, 25, and 30%. Ternary mixes were generated at rates of 5, 10, 15, 20, and 25% DP and 25, 20, 15, 10, and 5% SF, respectively. The compressive and flexural strength of water-cured SCM samples were measured at 3, 28, and 180 days of age. Mechanical performance of 28-day water-cured SCMs specimens was also evaluated after 180 days of exposure to MgSO4 solution. The transport features and sorptivity of water-cured SCMs samples for 28 days were also assessed. Microstructural characteristics using SEM were analyzed. The results demonstrate that all SCM mixtures containing DP and DP + SF have viscosity values higher than the reference mixture. The experimental results exhibited that very good compressive strength performance was gained for the binary SCMs up to 30% DP content at a late age of 180 days. At a long curing age of 180 days, using DP instead of cement up to 30% only slightly decreased the compressive strength by 15%. According to the findings, the specimens that had cement substituted with a 20% DP and 10% SF mixture had superior mechanical properties than the other ternary and most of binary SCMs specimens. The mixture DP20SF10 had the best compressive strength performance. All binary and ternary SCMs exhibited good sulfate resistance.