Current Concepts in Engineering Research and Technology Vol. 3

Concrete production relies heavily on cement, which is costly and contributes to environmental pollution through carbon emissions during manufacture. The growing demand for sustainable construction materials has encouraged the use of alternative cementitious materials. This study investigated the feasibility of using Crumb Tire Ash (CTA) as a partial cement replacement in concrete and evaluated its effects on workability, compressive strength and split tensile strength. Discarded waste tyres were collected from local vulcanisers and recycling centres. CTA was produced by burning and milling waste tyre rubber into fine ash. Laboratory tests, including specific gravity, sieve analysis, slump flow, V-funnel and L-box tests, were conducted to assess the physical and rheological properties of the concrete. Cement was replaced with CTA at 0%, 5%, 10% and 15%, and specimens were cured for 7, 21 and 28 days. The results showed that CTA-modified concrete satisfied fresh concrete requirements; however, increasing CTA content reduced filling and passing ability. The density of the concrete increased with curing age and replacement level but remained within the normal-weight range. The highest average compressive strength at 28 days was obtained at 10% CTA replacement (21.57 N/mm²), compared with 21.18 N/mm² for the control. At 28 days, the 10% CTA mix also recorded the highest split tensile strength (23.57 N/mm²). The findings indicate that 10% CTA is the optimum replacement level within the investigated range, while higher replacement levels adversely affect workability and strength.