Optimizing the Lightweight Steel Fibre Reinforced Bacterial Concrete With Nano-Silica and Coconut Shell Aggregates Using Taguchi Method

Concrete is essential for construction due to its high strength and durability. It supports most modern infrastructure globally. Cement production is a major source of CO₂ emissions, posing serious environmental concerns. Additionally, the rising demand for concrete is straining the limited supply of essential raw materials, such as aggregates. Researchers are examining alternative materials to improve Sustainability while maintaining structural strength to address these issues. This research aims to improve concrete performance by enhancing cement durability with nano-silica. Coconut shell, an agricultural by-product, functions as an eco-friendly alternative to conventional coarse aggregates, alleviating their scarcity. Microbiologically induced calcium carbonate precipitation (MICP) was employed to develop a lightweight steel fibre-reinforced bacterial concrete. The mix incorporated Bacillus subtilis at varying concentrations (10⁶, 10⁷, and 10⁸ CFU/ml), nano-silica at 1%, 2%, and 3% by weight of cement, and water/cement ratios of 0.40, 0.42, and 0.44. Coconut shells were used entirely in place of coarse aggregates, and steel fibres were added at 1%, 2%, and 3% by weight of cement to improve strength. The Taguchi method and an L9 orthogonal array were used to identify optimal conditions for enhancing compressive strength and durability. A scanning electron microscope (SEM) was used to analyse the control and optimised mixes. The results showed that using 2% nano-silica, 100% coconut shell aggregate, Bacillus subtilis at 10⁷ CFU/ml, and a 0.42 water/cement ratio significantly improved strength and durability. SEM analysis revealed calcium carbonate (CaCO₃) precipitation in the optimised mixture, confirming the treatment’s effectiveness.