Effect of Coir Fibre Ash (CFA) on the strengths, modulus of elasticity and embodied carbon of concrete using response surface methodology (RSM) and optimization

With an embodied carbon content of 0.93 kg CO2/kg, cement is an essential component of concrete. As the global demand for concrete construction is rising, research is being conducted to replace cement with supplementary cementitious materials (SCMs). A variety of SCMs are identified as having positive impacts on the concrete's compressive strength and embodied carbon. Coir Fibre Ash (CFA) is well known in SCM from existing research, but its use in concrete has not been investigated from an embodied carbon perspective before. The paper adopts an experimental methodology involving CFA as SCM at 3%, 6%, 9%, 12%, 15%, and 18% of 576 kg cement for each m3 of concrete. CFA was therefore added. The study aimed to find out the impact of the addition of CFA in concrete on compressive strength (CS), flexural strength (FS), splitting tensile strength (STS), and modulus of elasticity (MOE). The determination of embodied carbon was made, and RSM was used to develop the model with maximum accuracy. Samples were prepared for 7, 14, and 28 days. CFA was found to be positively affecting CS, FS, STS, and MOE till 9%, after which, because of the dominance of silica dioxide in CFA, it did not show any improvement. Embodied carbon was found to be decreasing with the increasing addition of CFA. RSM results followed by optimization provided highly validated equations for predicting the CS, FS, STS, and MOE of con-crete by just using the value of CFA as SCM.

Automated summary

Research has shown that adding Coir Fibre Ash (CFA) as supplementary cementitious material can improve the compressive strength and reduce the embodied carbon of concrete. The optimal impact on concrete performance is achieved with a 9% addition of CFA, while excessive addition results in performance decline. A method to predict the performance of concrete, such as compressive strength, using CFA as a supplementary cementitious material has been proposed.