Performance Evaluation and Microstructural Analysis of Concrete Containing Metakaolin and Neem Seed Ash.

Abstract

This experimental research assessed the performance of concrete containing Metakaolin (Mk) and Neem Seed Ash (NSA). Portland Limestone Cement was partially replaced by metakaolin and neem seed ash at different proportions in concrete. The performance of the admixtures in concrete mixtures was assessed in terms of mixture workability (Slump test) and strength (compressive and tensile strength) properties. The result of the slump test for the Mk/NSA concrete showed that they were workable. The result was 42 mm for control, Mk 2.5%, NSA 2.5% was 44 mm, Mk 5%, NSA 5% was 48 mm, 7.5% Mk, 7.5% NSA was 51 mm, and 10% Mk, 10% NSA was 55 mm. The higher the replacement of cement with Mk/NSA, the higher the slump value. The consistency of cement was 29% and increased with increasing NSA and Mk content. At replacement of cement by Mk/NSA at 5, 10, 15 and 20%, the consistency values were 31, 33, 35 and 38%. Optimization of compressive and tensile strength of the admixed concrete by Response Surface Methodology was done using Box-Behnken Design (BBD). The optimal result obtained was 5% Mk and 5% NSA at 80 days of curing gave maximum compressive strength of 34.2 N/mm² and tensile strength of 3.5N/mm². BBD was used for analysis of variance and for developing model equations for compressive and tensile strength.  Microstructural analysis of the admixed concrete showed a denser and reduced pore structure compared to the control sample. It was concluded that Mk and NSA are useful materials in production of viable and cost-effective concrete. Further research should be carried out to evaluate the effects of NSA in ternary mixture with other waste agricultural or industrial materials in concrete production.