COMPRESSIVE STRENGTH

This research investigated the utilization of polypropylene (PP) waste as an additive in the production of sandcrete blocks, aimed at promoting sustainable waste management and reducing the environmental impact of plastic pollution. The study sought to determine the influence of varying polypropylene waste contents on the physical and mechanical properties of sandcrete blocks, thereby evaluating its suitability as a construction material modifier. The experimental work involved producing paving stone specimens with 0%, 1%, 2%, 3% and 4% polypropylene waste by weight of sand. Aggregates were first characterized through specific gravity and sieve analysis to ensure conformity with standard specifications. Sandcrete blocks were then cast, cured in water, and tested for water absorption and compressive strength at 3 and 7 days of curing, following procedures outlined in relevant British Standards. This methodology ensured uniformity in mixing, curing and testing, allowing a clear assessment of polypropylene’s effect on the samples’ performance. The results showed the polypropylene addition influenced both durability and strength properties. Water absorption ranged between 0.64% and 2.88% with the lowest value recorded at 4% PP content, suggesting improved impermeability at higher plastic dosages. Compressive strength ranged from 11.41Mpa and 16.07Mpa, with optimum strength achieved at 1% PP addition, after which a gradual reduction is observed. It was concluded that the inclusion of polypropylene waste up to 1% can enhance strength and durability without compromising structural performance. The study recommends using low dosages of polypropylene waste in sandcrete blocks production and encourages further research into improving interfacial bonding through surface modification and longer curing periods to
maximize the material’s potential for sustainable construction.

This study evaluated the compressive strength of coconut shell concrete for concrete construction by partially replacing coarse aggregate with crushed coconut shells at varying levels (0%, 5%, 10%, and 15%). The primary aim was to determine the optimum replacement percentage that delivers satisfactory mechanical performance including compressive strength, split tensile strength, and flexural strength while promoting sustainability and reducing concrete weight. This investigation is driven by the need to recycle agricultural waste and improve the environmental footprint of conventional concrete in harsh service conditions. A series of experiments were conducted on concrete mixes with replacement levels of 0%, 5%, 10%, and 15% by weight, prepared with a constant water-to-cement ratio of 0.48. Fresh concrete workability was assessed using slump tests, which indicated a reduction in
slump as the percentage of coconut shell replacement increased. Hardened concrete specimens were cast in cube form and cured for 7, 14, and 28 days. Compressive strength tests were then carried out using a universal compression testing machine with a 2000 kN capacity. The failure load of each cube was recorded, and compressive strength was calculated using the formula: Strength = (Maximum Load)/(Cross-sectional Area). The results show that the control mix (0% replacement) achieved average compressive strengths of 21.09 N/mm² at 7 days, 23.90 N/mm² at 14 days, and 30.51 N/mm² at 28 days. Although increasing coconut shell content resulted in higher water absorption and a slight reduction in workability, the mix with 5% replacement maintained compressive strength values closest to the control, while meeting the target design characteristic strength (approximately 20 N/mm²). These findings indicate that a 5% replacement level provides the optimal balance between sustainability and mechanical performance, making coconut shell concrete a viable alternative for concrete applications.