Response Surface Methodology: The Improvement of Tropical Residual Soil Mechanical Properties Utilizing Calcined Seashell Powder and Treated Coir Fibre

Calcined seashell (CSS) powder and treated coir fibre (CF) are well-established additives for reinforcing poor soils. However, the absence of specific mix designs to optimize makes it difficult predict their combined effect on improving mechanical behaviour This research explores use response surface methods find optimal proportions CSS CF enhancing properties a tropical residual soil. study uses combination Analysis Variance (ANOVA) regression models examine how independent variables content, curing duration influence responses Unconfined Compressive Strength (UCS), Flexural (FS), Indirect Tensile (ITS). The findings show that 9.06% CSS, 0.30% CF, 12 days significantly improved UCS, FS, ITS by roughly six, four, three times, respectively. Microstructural analysis revealed formation calcium-aluminate-hydrate calcium-silicate-hydrate primary components responsible enhanced