An Experimental Investigation on Partial Replacement of Cement by Metakaolin and Coarse Aggregate by Iron Slag on M25 Grade Concrete

Abstract

This study investigates the properties of M25 grade concrete, Cement as a partial replacement by Metakaolin and coarse aggregate by iron slag. Metakaolin is a dehydroxylated form of the Kaolin clay mineral. Various concrete mixtures were prepared by replacing cement with Metakaolin at varying percentages like 5%,6%,7% and 8% while maintaining the water-cement ratio. With optimum percentage of Metakaolin, various concrete mixes were prepared by replacing coarse aggregate by iron slag at percentages 10%, 20%, 30% ,40% and 50%. The experimental program included tests for compressive strength and flexural strength at different curing ages 7, 28, 56 and 90 days.

Introduction

The text presents an experimental study on improving the mechanical performance and sustainability of concrete by partially replacing cement with metakaolin and coarse aggregate with iron slag. Since conventional cement production releases large amounts of CO?, the use of alternative and industrial by-product materials such as metakaolin and iron slag helps reduce environmental impact while enhancing concrete properties.

The literature review highlights previous studies showing that waste materials like rice husk ash, steel/iron slag, metakaolin, silica fume, and glass powder can significantly improve compressive, tensile, and flexural strength of concrete when used at optimal replacement levels, while also promoting eco-friendly construction practices.

In the experimental investigation, M25 grade concrete was prepared using Ordinary Portland Cement (43 grade). Cement was replaced with metakaolin at levels of 0%, 5%, 6%, 7%, and 8% to determine the optimum percentage. Based on compressive strength results, 6% metakaolin was found to be optimal. Using this optimum metakaolin content, iron slag was then used as a replacement for coarse aggregate at 10%, 20%, 30%, 40%, and 50% to identify the best proportion.

Test results showed that concrete with 6% metakaolin exhibited significantly higher compressive strength than conventional concrete at all curing ages, reaching up to 52.5 MPa at 90 days. When combined with iron slag, the mix containing 6% metakaolin and 40% iron slag achieved the highest compressive and flexural strength. The improvements are attributed to the pozzolanic action of metakaolin, which enhances the concrete microstructure, and the dense packing and interlocking effect of iron slag.

Overall, the study concludes that replacing cement with 6% metakaolin and coarse aggregate with about 40% iron slag produces stronger, more durable, and environmentally sustainable concrete, making it a viable alternative to conventional concrete materials.

Conclusion

1) The compressive strength of concrete with 6% Metakaolin in cement increases the strength up to 53% when compare to normal concrete at 28 days. 2) The compressive strength of concrete with 6% Metakaolin and 40% iron slag increases the strength up to 47% when compare to normal concrete at 28 days. 3) The flexural strength of concrete contains 6% Metakaolin increases the strength up to 12% will compare to normal concrete. 4) The flexural strength of concrete contains 6% Metakaolin and 40% iron slag increases the strength up to 4% when compare to normal concrete.

References

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Copyright

Copyright © 2025 D. Hema Sai Reddy, T. Thandava Krishna, Dr. B. Madhusudana Reddy. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.