Determination of Optimal Mix Design for Self-Compacting Concrete Using Metakaolin from Kogi State

This study determines an optimal mix design for self-compacting concrete (SCC) incorporating metakaolin (MK) produced by calcination of kaolin sourced from Kogi State, North Central Nigeria. Self-compacting concrete offers significant advantages in terms of construction productivity and finish quality in reinforced structures, and the use of locally produced metakaolin as a supplementary cementitious material aligns with efforts to reduce OPC consumption in Nigerian construction. Kaolin is calcined at 800 degrees Celsius for 2 hours to produce reactive metakaolin, which is characterised by XRF, XRD, and BET surface area analysis. Metakaolin is substituted for OPC at 5, 10, 15, and 20 percent replacement levels. SCC mixes are designed following EFNARC guidelines, with fresh state properties evaluated by slump flow, V-funnel, and L-box tests. Hardened properties including compressive strength, flexural strength, and sorptivity are measured at 7, 28, and 56 days. Findings indicate that MK replacement at 10 to 15 percent satisfies EFNARC viscosity and flowability criteria while achieving 28-day compressive strength above 35 MPa, meeting structural concrete requirements. Sorptivity decreases with increasing MK content up to 15 percent, reflecting pore refinement by the pozzolanic reaction. Replacement above 15 percent reduces flowability below acceptable limits. Keywords: self-compacting concrete, metakaolin, supplementary cementitious material, mix design, Kogi State.