ESTIMATING THE OPIMUM WATER-CEMENT RATIO OF DIFFERENT CONCRETE GRADES

The characteristics of both fresh and hardened concrete are significantly affected by the watercement ratio. In this particular study, water-cement ratios of 0.3, 0.4, 0.5, and 0.6 were utilized. Concrete grades 15, 20, and 25 were employed, accompanied by a coarse aggregate size of 12.7mm. For each water-cement ratio, nine cubes were cast, and subsequently, three cubes were crushed for curing periods of 7 days, 21 days, and 28 days. The study focused on analyzing both compressive strength and workability. The compressive strength results at 7 days for concrete grade 15, 20 and 25 spanning water-cement ratios from 0.3, 0.4, 0.5 and 0.6 are 10.74 N/mm2, 10.37N/mm2, 9.74 N/mm2, 9.43 N/mm2 13.03 N/mm2, 12.43 N/mm2, 11.88 N/mm2, 11.47 N/mm2 16.15 N/mm2, 15.41 N/mm2, 14.77 N/mm2 and 14.61 N/mm2 respectively, for 21 days; 13.8 N/mm2, 13.41 N/mm2, 12.64 N/mm2, 12.29 N/mm2, 18.3 N/mm2, 17.3 N/mm2, 16.87 N/mm2, 16.32 N/mm2, 19.73 N/mm2, 19.13 N/mm2, 18.52 N/mm2 and 17.91 N/mm2 respectively and at 28 days; 18.22 N/mm2, 17.48 N/mm2, 16.55 N/mm2, 16.16 N/mm2, 23.1 N/mm2, 22.60 N/mm2, 22.15 N/mm2, 21.8 N/mm2, 27.71 N/mm2, 27.08 N/mm2, 26.34 N/mm2 and 25.78 N/mm2 respectively. These results indicate a decrease in compressive strength with an increase in water-cement ratio for the different concrete grades. Regarding fresh concrete, the slump results for 0.3, 0.4, 0.5 and 0.6 water-cement ratios for grade 15, 20 and 25 concrete respectively were: 37mm, 43mm, 50mm, 51mm, 39mm, 47mm, 53mm, 58mm, 44mm, 51mm, 57mm and 60mm respectively. It's observed that an increase in water-cement ratio directly corresponds to an increase in workability of the concrete