Engineering attributes of coir fibre ash incorporated sustainable lime concrete

Lime is an important ingredient in lime concrete, with a carbon content of 0.76 kg CO₂/kg. As the global consumption of structural concrete increases, studies are being performed to substitute lime with byproducts such as coconut fibre ash. A collection of waste materials in the form of ash or powder has been recognised to have positive effects on the mechanical properties of concrete and its embodied carbon. However, engineering properties in lime concrete are found to be positively affected by many lime composite materials. While previous studies have made Coir Fibre Ash (CFA) well-known in cementitious material, its potential usage in lime concrete has not yet been explored from a modern applications standpoint. Instead of using the well-established empirical modelling testing approach, such as the further Response Surface Methodology (RSM), the key mechanical characteristics of lime concrete amended with CFA cannot be accurately modelled. This article employs an empirical approach to investigate the impacts of substituting lime with CFA across a range of percentages, including 3%, 6%, 9%, 12%, 15%, and 18% in lime concrete. Compressive strength (CS), flexural strength (FS), splitting tensile strength (STS), and modulus of elasticity (MOE) were investigated as potential outcomes of CFA incorporation into concrete. Embodied carbon was calculated, with RSM applied to refine the model to within a margin of error. Samples were collected at 7, 14, and 28 days. CFA was shown to have a beneficial effect on CS, FS, STS, and MOE up to 6%; however, due to the prevalence of silica dioxide in CFA and the high quantity of CaO in lime, no further improvement was seen beyond that point. Moreover, embodied carbon and eco-strength productivity indicated considerable improvement in modified lime concrete, confirming high sustainability. All the study's variables were determined to have statistically significant correlations. Concrete's CS, FS, STS, and MOE may be predicted with great accuracy using just the value of CFA as lime composites, thanks to the findings of a response surface methodology (RSM) followed by an optimization process.