INVESTIGATION OF RUBBER TIRE WASTE AND PALM KERNEL SHELL AS A PARTIAL REPLACEMENT FOR COARSE AGGREGATE IN CONCRETE PRODUCTION.

ABSTRACT The increasing demand for sustainable construction materials has intensified research into the utilization of agricultural and industrial waste products in concrete production. This study investigated the effects of partial replacement of conventional concrete constituents with Rubber Tyre (RT) and Palm Kernel Shell (PKS) on the workability, density, and compressive strength of concrete. Concrete specimens were produced using varying replacement levels of RT and PKS, both individually and in combined proportions, while a control mix with 0% replacement was used for comparison. Standard laboratory tests were conducted in accordance with relevant codes. The slump test was carried out to evaluate workability, while density and compressive strength tests were performed on concrete cubes cured for 7, 14, 21, and 28 days. The results revealed that workability decreased progressively with increasing replacement levels of RT and PKS, as indicated by reduced slump values. This reduction was more pronounced at higher replacement levels due to the irregular shape and surface characteristics of the replacement materials. Concrete density also decreased with increasing RT and PKS content, reflecting the lightweight nature of the materials. However, mixes containing 10% PKS and 5% RT + 5% PKS maintained densities comparable to the control mix. Compressive strength increased with curing age for all mixes. The control mixes consistently recorded the highest strength values, while concrete containing 10% PKS replacement exhibited compressive strength values closest to the control, particularly at 28 days. Higher combined replacement levels resulted in a significant reduction in strength, limiting their suitability for structural applications. The study concludes that partial replacement of conventional materials with RT and PKS is technically feasible at low replacement levels, with 10% PKS identified as the optimum replacement level for balancing mechanical performance, workability, and sustainability. The findings demonstrate the potential of RT and PKS as alternative materials for producing lightweight and environmentally sustainable concrete suitable for non-load-bearing and low-stress structural applications.