Vol. 2 No. 01-29 (2025): THE IMPACT OF WATER-CEMENT RATIO ON CONCRETE PROPERTIES MADE WITH HAND CRUSHED AND MACHINE CRUSHED AGGREGATES

This study seeks to provide insight into how varying water cement ratios (0.40, 0.45 and 0.50) influence the properties of fresh and hardened concrete made with aggregates prepared using two different preparation methods (manual and mechanical) both experimentally and statistically. Concrete properties evaluated included workability, density, compressive and flexural strengths at 7, 14, 21 and 28 days of curing. Results revealed that varying the water-cement ratio impacted both fresh and hardened concrete properties while concrete having low water cement ratio performed better for both aggregates. Although handcrushed aggregates had slightly higher percentage gains in compressive strength over time, the machine-crushed aggregates started at a much higher strength. The flexural strength increased over time, with machinecrushed aggregates exhibiting a faster rate of gain while early-age differences were minimal, the disparity became more pronounced at 21 and 28 days. For all w/c ratios, machine-crushed aggregates consistently demonstrated lower water absorption compared to those with handcrushed aggregates at later ages. ANOVA and the independent samples t-Tests were employed to statistically verify these effects. A significant impact of water cement ratio and curing age was observed on the compressive strength, flexural strength and density while water absorption was significantly less impacted. The independent samples tTest showed a significant difference between the mean values for compressive strength, flexural strength and density (p < 0.001), with machine-crushed concrete consistently outperforming hand-crushed concrete. Water absorption, however, showed no statistically significant difference (p = 0.689), suggesting that both aggregate types absorb water at comparable rates