Investigation of Effect on Strength Parameters of Concrete by Replacing Ingredients by Environment-friendly Materials

Abstract

This project looks at how we can make M20 grade concrete more environmentally friendly by changing some of its basic ingredients without losing strength. In place of using only ordinary cement and natural stone, part of the cement is replaced with fly ash and GGBS, and part of the coarse aggregate is replaced with coconut shells, which are usually treated as waste. The work includes testing all the materials, designing mixes as per IS 10262:2019, preparing both modified and conventional concretes, and then checking slump, density, and compressive, split tensile, and flexural strength at different ages. The results show that the modified concrete can still meet M20 strength requirements, has slightly lower weight, and benefits from the combined effect of the added materials, while a basic cost comparison indicates that higher replacement levels can also reduce overall concrete cost. Overall, the study suggests that using industrial by-products and agricultural waste in concrete is a practical way to support more sustainable and economical construction.

Introduction

Concrete is a widely used construction material valued for strength, durability, and versatility. However, cement production and raw material extraction contribute significantly to carbon emissions and environmental degradation. This study investigates eco-friendly, low-carbon alternatives by partially replacing cement with fly ash (FA) and ground granulated blast furnace slag (GGBS), and substituting part of coarse aggregates with coconut shells, aiming to balance strength, durability, sustainability, and cost.

Materials and Methods:

• Cement: OPC 53 Grade with partial replacement using FA and GGBS.

• Aggregates: River sand (fine aggregate), crushed stone (coarse aggregate), and coconut shells (partial coarse aggregate replacement).

• Water: Potable water (w/b ratio = 0.4).

• Admixture: Polycarboxylate-based superplasticizer (≤0.8%).

Tests conducted:

• Specific gravity, fineness, water absorption, impact value, setting times, and grading as per IS codes.

• Workability assessed using slump test.

• Mechanical properties tested: compressive strength, flexural strength, and split tensile strength using standard cube, cylinder, and prism molds.

Concrete Mixes:

Test Results:

1. Workability (Slump Test)

   • Conventional: 85 mm

   • Mix 1: 79.7 mm (slightly lower)

   • Mix 2: 85 mm

2. Compressive Strength (28 days)

   • Conventional: 22.9 MPa

   • Mix 1: 20.6 MPa

   • Mix 2: 21.9 MPa

3. Flexural Strength (28 days)

   • Conventional: 3.23 MPa

   • Mix 1: 3.0 MPa

   • Mix 2: 3.3 MPa

4. Split Tensile Strength (28 days)

   • Conventional: 2.17 MPa

   • Mix 1: 2.0 MPa

   • Mix 2: 2.2 MPa

Observations:

• All mixes achieved acceptable workability for M20 grade concrete.

• Partial replacement of cement with fly ash and GGBS slightly reduced strength but remained above the required threshold, showing that eco-friendly mixes can be both sustainable and structurally adequate.

• Mix 2 (10% FA + 10% GGBS) offered better balance between workability and strength compared to Mix 1.

• Use of coconut shell aggregates reduced density while maintaining mechanical performance.

Conclusion

This study examined the possibility of producing eco-friendly M20 grade concrete by partially replacing ordinary Portland cement with fly ash and GGBS, and coarse aggregate with coconut shell aggregate. Based on the experimental results, it was observed that the modified concrete was able to achieve the required strength for M20 grade at 28 days. Although the early-age strength was slightly lower compared to conventional concrete, the later-age strength improved due to the pozzolanic reaction of fly ash and GGBS. The use of coconut shell aggregate reduced the overall density of concrete, resulting in a lighter mix while still maintaining acceptable mechanical properties. Workability was slightly reduced but was successfully controlled using superplasticizer. Overall, the results indicate that industrial by-products and agricultural waste materials can be effectively used in concrete without significantly affecting strength performance. In addition to meeting structural requirements, the modified mix contributes to reduced environmental impact and potential cost savings. Therefore, the use of such eco-friendly materials can be considered a practical and sustainable alternative for future construction practices.

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Copyright

Copyright © 2026 Nilesh Vishwas Avhad, Pushpendra Kumar Kushwaha, Mithun Kumar Rana. 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.