Experimental Study on the Effect of Silica Fume on Strength and Durability of M40 Grade Ready Mix Concrete

Abstract

The present research investigates the influence of silica fume as a partial replacement of cement on the mechanical and durability properties of M40 grade Ready Mix Concrete (RMC). Five concrete mixes were designed with 0%, 5%, 10%, 15%, and 20% silica fume by weight of cement. The experimental program involved testing for compressive strength, split tensile strength, flexural strength, water absorption, acid resistance, and chloride permeability at various curing ages (7, 28, and 56 days). Results indicate that the mechanical strength and durability characteristics improved significantly up to a 10% replacement level, beyond which a decline was observed. The 10% silica fume mix exhibited the highest 28-day compressive strength of 50.9 MPa, about 11.6% higher than the control mix, along with reduced water absorption (2.35%) and chloride permeability (1850 Coulombs). The findings confirm that silica fume enhances the microstructure and durability of concrete and is suitable for high-performance and sustainable construction applications.

Introduction

Concrete is a widely used construction material, but its low tensile strength and high permeability limit its long-term performance. To improve sustainability and durability, this study examines the use of silica fume, a highly reactive ultrafine pozzolanic by-product, as a partial replacement for cement in M40 grade Ready Mix Concrete (RMC). Silica fume enhances strength and durability by forming additional C–S–H gel and refining the pore structure, reducing permeability, chloride ingress, and acid attack.

The study investigates silica fume replacement at 0%, 5%, 10%, 15%, and 20%, using materials compliant with Indian Standards (IS 10262:2019, IS 516:1959, IS 456:2000). Tests conducted include compressive, split tensile, and flexural strength, along with water absorption, acid resistance, and chloride permeability.

Results show that mechanical properties—compressive, tensile, and flexural strength—all increase with silica fume addition up to 10%, after which strength declines due to reduced workability and incomplete hydration. At 10% replacement, concrete achieves the highest 28-day compressive strength (50.9 MPa), split tensile strength (4.10 MPa), and flexural strength (6.35 MPa).

Durability characteristics also improve significantly at 10% silica fume, with the lowest water absorption (2.35%), minimal acid-induced weight loss (1.90%), and the lowest chloride permeability (1850 Coulombs). Beyond 10%, durability performance begins to drop.

Conclusion

1) The inclusion of silica fume reduced workability but enhanced strength and durability when combined with superplasticizers. 2) The 10% silica fume replacement achieved maximum compressive strength (50.9 MPa at 28 days), about 11.6% higher than the control mix. 3) Split tensile and flexural strengths also improved by approximately 9–10% at the same replacement level. 4) Durability characteristics such as water absorption, chloride permeability, and acid resistance improved significantly at 10% replacement. 5) The microstructural densification due to the pozzolanic and filler effects of silica fume contributed to improved impermeability and reduced porosity. 6) The 10% silica fume mix is recommended for high-performance and sustainable RMC applications.

References

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Copyright

Copyright © 2025 Mohd. Ammaruddin, Harshit Bhilawe, Abhay Sahare, Sanket Narnaware, Prof. Atul D Gautam. 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.