Metakaolin –A Partial Replacement of Cement in Concrete as Admixture
DOI:
https://doi.org/10.5281/zenodo.17848050Keywords:
Concrete, Flexural Strength, Metakaolin, Pozzolanic Reaction, WorkabilityAbstract
The use of supplementary cementitious materials has become an important approach for improving the performance and sustainability of concrete. Among these materials, metakaolin—produced by controlled calcination of kaolin clay—offers high pozzolanic reactivity and the potential to enhance strength and durability. This study evaluates the influence of metakaolin as a partial replacement for ordinary Portland cement in M25 concrete. Replacement levels of 5%, 10%, 15%, and 20% were tested to determine their effects on workability and mechanical properties. Concrete specimens were prepared and subjected to slump and compaction factor tests in the fresh state, followed by compressive, split tensile, and flexural strength tests at 3, 7, and 28 days. Workability was found to decrease slightly with increasing metakaolin content, though all mixes remained workable. The mechanical test results showed a clear improvement in strength for mixes containing metakaolin, with the 10% replacement level providing the highest enhancement across all strength parameters. This improvement is attributed to the pozzolanic reaction, which reduces calcium hydroxide and forms additional C–S–H gel, resulting in a denser and stronger microstructure. Based on the findings, metakaolin can be considered an effective mineral admixture for producing stronger and more durable concrete. The study identifies 10% replacement as the optimum level for achieving maximum performance benefits while maintaining acceptable workability.
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References
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