Partial Replacement of Plastic Waste and Coconut Fibre in Concrete

Abstract

The increasing demand for concrete in the construction industry, coupled with the overuse of natural resources and rising environmentalconcerns, has necessitated the development of sustainable alternatives. This research project focuses on the partial replacement of cement with coconut fiber powder and fine aggregate withHDPE plastic waste (10 mm flakes) in M25 grade concrete. The primary aim is to reduce the environmental burden associated with cement production and plastic pollution while maintaining the required mechanical properties of concrete. The experimental program involved preparing concrete mixes with varying proportions ofcoconutfiberpowder (0%,0.5%,0.8%,1.0%, and 1.5%) and HDPE plastic waste (0%, 5%, 10%, and 15%). A total of 36 cube specimens were cast and tested for compressive strength at 7, 14, and 28 days of curing. The optimal results were observed for the mix containing 1% coconut fiber and 10% plastic waste, which achieved a compressive strength of 26.8 N/mm² at 28 days—exceeding the minimum requirement for M25 concrete. Additionally, the use of a superplasticizer of Polycarboxylate ether further enhanced the strength to 28.5 N/mm². The findings confirm that coconut fiber and plastic waste can be effectively used as partial replacements for cement and sand without compromising the strength or performance of concrete. This study demonstrates the potential of converting agricultural and industrial waste into valuable resources for eco-friendly, cost-effective, and sustainable construction.

Introduction

Concrete is the most widely used construction material, but its production has significant environmental impacts due to heavy reliance on non-renewable resources (like limestone and river sand) and high CO? emissions. Simultaneously, improper disposal of plastic waste and agricultural by-products, such as coconut husk, poses serious pollution issues.

This study explores sustainable concrete by:

• Replacing cement partially with coconut fiber powder, and

• Replacing fine aggregate (sand) with shredded HDPE plastic waste (10 mm particles).

The objective is to evaluate the mechanical performance (mainly compressive strength) of M25 grade concrete with these replacements over 7, 14, and 28 days. A superplasticizer is also used to enhance workability and strength.

Key Objectives:

1. Assess the effects of coconut fiber powder as a cement substitute.

2. Evaluate HDPE plastic waste as a fine aggregate substitute.

3. Measure compressive strength over different curing periods.

4. Identify optimal replacement percentages for strength and workability.

5. Promote sustainable construction by reusing waste materials.

Literature Insights:

• Coconut shell and fiber improve strength, reduce cost, and enhance sustainability.

• Plastic waste (e.g., HDPE, PET, LDPE) as aggregate substitute yields lighter, thermally efficient, and low-absorption bricks.

• Optimal replacement (typically up to 20%) enhances strength, though excessive amounts may reduce it slightly.

Materials Used:

• Cement – Binding agent.

• River Sand – Fine aggregate.

• Gravel – Coarse aggregate.

• Water – Essential for hydration and strength.

• HDPE Plastic Waste – Replaces part of fine aggregate.

• Coconut Fiber Powder – Replaces part of cement; improves crack resistance and bonding.

Conclusion

This chapter summarises the key findings from the experimental investigation on the partial replacement of cement with coconut fiber powder andfineaggregatewithHDPEplasticwasteinM25 grade concrete. The study also evaluated the effect of adding a superplasticizer to the optimal mix. A. Conclusions Based on the results and analysis of compressive strength testing at 7, 14, and 28 days, the following conclusions can be drawn: 1) ?UseofCoconutFiberPowder: • Replacing cement with coconut fiberpowder up to 1.0% resulted in improved compressive strength across all curing periods. • At 1.0%, the compressive strength at 28 days reached 24.37 N/mm², higher than the control mix (22.6 N/mm²). • Beyond1.0%,strengthdecreased,likelydue to poor bonding and increased internal porosity caused by excess fiber. 2) UseofHDPEPlasticWastewithCoconut Fiber: • Replacing fine aggregate with HDPE plastic waste at 10% in combination with 1% coconut fiber achieved the best performance: 26.8 N/mm² at 28 days. • The mix exhibited good compaction, uniformity,andminimalvisiblesegregation. • Strengthdeclinedslightlyat15%plasticdue to possible interference with cement paste bonding. 3) Useof Superplasticizer: • Incorporating a superplasticizer (at 10% dosage) into the 1% coconut fiber + 10% HDPE mix further enhanced the concrete performance. • The compressive strength increased to 28.5 N/mm² at 28 days, and workability also improved notably. • Superplasticizershelped inreducinginternal voids and enhancing particle dispersion, especially beneficial in fiber and plastic- containing concrete. 4) OverallObservations: • The mix with 1% coconut Fiber powder and 10% plastic waste, with or without superplasticizer, meets the strength requirements for M25 concrete. • All modified mixes (except the one with 1.5% Fiberonly) surpassed the minimum 25 MPa requirement at 28 days. • WastematerialslikecoconutcoirandHDPE can be effectively utilized in structural concrete up to certain limits without compromising on strength. B. Recommendations Based on this study, the followingrecommendations are proposed: 1) OptimalMixProportion: • Use 1% coconut fibre powder as partial cement replacement. • Use 10% HDPE plastic flakes (10 mm) as partial fine aggregate replacement. • Addition of superplasticizer is advisabletoenhanceworkabilityand compressive strength. 2) Applications: • Suitable for non-load-bearing walls, partition blocks, low-rise buildings, and paver blocks. • Ideal for sustainable and low-cost construction in rural and semi-urban areas. 3) FurtherResearch: • Investigate long-term durability, shrinkage, and water absorption characteristics. • Explore the use of other admixtures or curing techniques to enhance performance. • Extend the study to include flexural and split tensile strength tests. 4) Environmental Benefit: • This approach provides an effective solution for managing agricultural and plastic waste. • Promotes eco-friendly construction and aligns with sustainable development goals (SDGs) and national missions like SwachhBharat Abhiyan.

References

[1] Santhoshkumar,D.,Rajesh,K.,&Yuvaraj,D. (2019). Experimental Study on Concrete Using Coconut Shell and Coir Fiber by Partial Replacement Method. IJARIIT.. [2] Sudha,T.etal.(2020).Studyonpaverblocks using coconut fibre. International Journal of Advance Research, Ideas and Innovations in Technology (IJARIIT). [3] Ravi Kiran, P., et al. (2021). Plastic Based Concrete Bricks. International Research Journal of Engineering and Technology (IRJET), Vol 8, Issue 1. [4] Rajarapu Bhushaiah, M., et al. (2019). Experimental Study on Manufacturing of Plastic Sand Bricks. International Research Journal of Engineering and Technology (IRJET), Vol 6, Issue 2. [5] G.Navya “Experimental Investigation on Properties of concrete paver block with inclusion of natural fiber” ISSN: 2248-9622, vol. 4, Issue 8, August 2014 [6] IS10262:2019.ConcreteMixProportioning–Guidelines.BureauofIndianStandards, New Delhi. [7] IS 383:2016. Specification for Coarse and Fine Aggregates from Natural Sources for Concrete. Bureau of Indian Standards, New Delhi. [8] IS516:1959.MethodsofTestsforStrengthof Concrete. Bureau of Indian Standards, New Delhi.

Copyright

Copyright © 2025 Depavath Jagan, Peddi Naveen Reddy, Barigela Rakesh, Erra Keerthana, Mangadudla Shirisha. 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.