Mechanical Properties of Palm Oil Waste Blended Cement-Based Concrete Containing Spent Garnet as Partial Fine Aggregate Replacement

The growing emphasis on sustainability in construction has sparked increased interest in sustainable materials, particularly the development of green concrete to address environmental concerns. Sand, a crucial component in various construction materials and industries, faces rising demand driven by population growth and improved living standards; however, its extraction can significantly disrupt river ecosystems. In Malaysia, spent garnet from ship sandblasting has emerged as a promising additive to enhance concrete performance, with research indicating its positive effects on compressive strength. This study investigates the effect of incorporating spent garnet as a partial replacement for fine aggregates on the mechanical properties of concrete. It aims to determine the optimum percentage of spent garnet that can effectively replace fine aggregates while achieving a concrete strength of 30 MPa within 28 days. The research utilizes water-cement ratios of 0.45, 0.50, and 0.55 in the mix design, alongside a conventional cement-sand ratio. Spent garnet is incorporated at varying percentages from 0% to 40%, with 10% palm oil fuel ash (POFA) substituting for cement. A total of 135 cubes and cylinders were prepared, and a slump test was conducted in accordance with ASTM C1437 standards. The specimens were cured in a tank for 7, 14, and 28 days before undergoing compressive strength and splitting tensile tests, following ASTM C109 specifications. The sieve analysis indicated that sand performs better than spent garnet, particularly at finer sieve sizes, where spent garnet underperforms. In terms of concrete workability, higher water-to-cement (w/c) ratios improved workability with increased spent garnet content, while lower ratios reduced it. The optimal compressive and splitting tensile strength was achieved with 30% spent garnet (SG) across all w/c ratios, although higher SG levels resulted in diminished strength. It is recommended that future research explore the long-term durability of concrete incorporating spent garnet and evaluate its environmental impacts more comprehensively. Additionally, further studies could investigate alternative sustainable additives and their combined effects on concrete performance to enhance sustainability in construction practices.