Synergistic influence of metakaolin and slag cement on the properties of self-compacting fiber-reinforced concrete

Self-compacting concrete (SCC) is a category of cement-based materials that need a high amount of binder to achieve the required characteristics. Various fine materials can be used to replace Portland cement (PC) and reduce the carbon footprint associated with cement manufacturing. In this research, the synergistic effect of metakaolin (MK) and ground-granulated blast-furnace slag (GGBS) on the fresh and hardened properties of SCC were investigated. In addition, steel fibers have been incorporated to evaluate their influence on fresh and hardened concrete properties. Several mixtures have been prepared incorporating different dosages of GGBS and MK as replacing materials to PC. Fresh SCC properties have been studied, including filling ability, viscosity, and passing ability. In addition, the hardened characteristics include mechanical properties, variation in compressive strength after high-temperature exposure, water penetration depth, and microstructures were investigated. The experimental results revealed that binary and ternary mixtures can achieve the requirements of SCC but with increasing the superplasticizer dosages. In addition, the incorporation of steel fiber reduces the concrete workability but at the same time has positive influences on the mechanical properties of concrete. Synergistic effect of MK and GGBS improves durability and mechanical properties in both cases: normal conditions and after high-temperature exposure. A combination of 15% GGBS and 10% MK gives better result in fresh and hardened properties.