Abstract

The mechanical properties of M25 grade concrete, with partial replacement of cement by Silica fume andcoarseaggregate by over burnt bricks. Various concrete mixtures were prepared by replacing cement with Silica fume at varying percentages (0%, 8%, 9%, 10%, 11%, and 12%) and over burnt bricks replacement by coarse aggregate at varying percentage (0%, 15%, 20%, 25%, 30% and 35%) while maintaining the same water-cement ratio. The results shows that the inclusion of Silica fume improves the compressive strength and flexural strength due to the pozzolanic reaction and pore refinement, whereas the replacement of coarse aggregate with overburnt bricks reduces the density but maintains same strength.This study concludes that a combination of 10% Silica fume and 25% overburnt bricks aggregate provides an eco-friendly and cost-effective alternativefor sustainable concrete production without reducing the strength requirements of M25 grade concrete.

Introduction

Concrete is a widely used construction material, but the use of natural aggregates and Portland cement leads to environmental problems such as high CO? emissions. To reduce these impacts, waste materials like brick powder, ceramic waste, metakaolin, and especially silica fume are used as partial replacements for cement, while waste bricks (over-burnt bricks) are used as recycled aggregates.

Literature Review Summary

1. Rachit Vyas et al.

   • Cement was partially replaced with 5–20% brick powder and 10% silica fume.

   • Workability decreased as brick powder increased.

   • Optimum replacement: 5–10% brick powder, giving good compressive, split tensile, and flexural strength.

   • Eco-friendly solution reducing cement consumption and pollution.

2. Rochak Pandey & Preeti Singh

   • Cement replaced with ceramic waste powder (10–30%) and metakaolin (10–20%), with 25% brick dust in fine aggregate.

   • Best performance at 20% ceramic powder + 15% metakaolin.

   • Improved strength and durability with reduced chloride penetration and water absorption.

3. S. Kanchidurai et al.

   • Over-burnt brick bats (OBB) used as coarse aggregate replacement at 0–100%.

   • 25% OBB gave the highest compressive strength.

   • Higher replacements (50%+) reduced strength.

   • Suitable for non-structural and mass concrete, promoting sustainability.

Experimental Investigation Summary

The study used M25 grade concrete with:

• OPC 43 grade cement

• Fine aggregate (FM = 2.78)

• Coarse aggregate (20 mm)

• Water–cement ratio = 0.49

Phase 1: Silica Fume Replacement

Concrete was tested with 0%, 8%, 9%, 10%, 11%, 12% silica fume.

• 10% silica fume gave the best compressive strength at all curing ages (7, 28, 56, 90 days).

• At 90 days, compressive strength reached 50.9 N/mm², higher than control mix.

Phase 2: Over-Burnt Brick Replacement

Using 10% silica fume as optimum, OBB replaced coarse aggregate at 15–35%.

• 25% OBB gave the optimum compressive strength at 7 and 28 days.

• Higher replacements reduced strength.

Combined Effect

Concrete with 10% silica fume + 25% OBB:

• Showed better compressive and flexural strength than the control mix.

• Produced lightweight concrete due to OBB’s lower density.

• More sustainable because it uses industrial waste and reduces cement usage.

However, durability tests showed that:

• Exposure to 5% HCl and MgSO? reduced strength and density compared to normal curing.

Conclusion

1) This investigation shows that results, can be use Silica fume and over burnt bricks. 2) The compressive strength of concrete with 10% Silica fume in cement, increases the strength up to 35% when compared to normal concrete at 28 days. 3) The compressive strength of concrete with 10% Silica fume and 25% over burnt bricks increases the strength up to 46% when compared to normal concrete at 28 days. 4) The flexural strength of concrete contains 10% Silica fume increases the strength up to 8.6% when compared to normal concrete. 5) The flexural strength of concrete contains 10% Silica fume and 25% over burnt bricks increases the strength up to 8.6% when compared to normal concrete. 6) When the 10% Silica fume concrete is cured at 5% HCL and MgSO4solution, it reduces the density and compressive strength when compared to normal curing.

References

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Copyright

Copyright © 2025 B. Pranav Naik, 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.