Exponential Models of Concrete Block Produced with Coconut Shell and Coconut Shell-Ash for Strength Characterization and Structural Stability

Abstract:

This study presents a novel approach to optimizing concrete block production by utilizing coconut shells and coconut shell ash as sustainable alternatives to stone dust and cement. Using classical experimental-mathematical modeling and exponential regression analysis, the optimal material proportions and their influence on the mechanical strength of concrete blocks were determined. Chemical composition tests indicated that incinerating coconut shells enhanced key pozzolanic components—silicon oxide, iron oxide, sulfur oxide, and potassium oxide—significantly improving the ash's pozzolanic reactivity and the durability of the concrete mix. The results reveal a critical threshold for incorporating these materials: beyond certain proportions, compressive strength declines. Specifically, strength ranged from 16.14 to 26.77 N/mm² at 100% replacement and from 0.32 to 1.54 N/mm² at 75% replacement. A non-linear regression model based on 42 observation points was developed, with 39 used for model training. The model accurately predicts performance and indicates an ideal mix consisting of 82.58% stone dust, a water–cement ratio of 0.6039, 82.5% cement, 17.5% coconut shell ash, and 17.42% coconut shells. This mix achieved a compressive strength of 3.17 N/mm² after 14 days of curing, exceeding the required 2.9 N/mm². The practical implications of these findings suggest that this mixture is cost-effective, utilizing low-cost coconut shells instead of more expensive materials like cement and stone dust. This approach promotes the use of sustainable materials in concrete production, supports waste management and conservation efforts, and aligns with circular economy practices in construction. Furthermore, the developed non-linear regression model serves as a valuable tool for integrating agricultural byproducts into concrete block production, providing a reliable method for predicting concrete performance and enabling better material selection in future applications. Generally, this study offers recommendations for identifying the optimal concrete block mix, enhancing circular economy practices, and minimizing dependence on non-renewable resources

• Periodical: International Journal of Engineering Research in Africa (Volume 75)
• Pages: 53-78
• DOI: https://doi.org/10.4028/p-SH603z
• Online since: October 2025
• Authors: Thompson Edozie Okeke*, Fidelis Onyebuchi Okafor, Michael Ebie Onyia
• Keywords: Classical Experimental-Mathematical Modeling, Coconut Shell, Coconut Shell Ash, Compressive Strength, Concrete Blocks, Economical Agricultural Byproducts, Exponential Regression

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