An experimental investigation on the effect of water/cement ratio on the compressive strength of ready mixed concrete designed by chemical admixture and different cements

In this study, an experimental investigation was conducted to investigate effect of water/cement ratio on the compressive strength of ready mixed concrete designed by using a chemical admixture and 3 different cements. For each cement type, 5 mixtures were designed with different water/cement (w/c) ratios varying from 0.3 to 0.7 without using admixture and 3 mixtures were designed with different w/c ratios varying from 0.5 to 0.3 by adding admixture. Compressive strength tests were carried out on the 50 mm cubic specimens at the ages of 7 and 28 days. Tests results revealed that when w/c ratio decreased from 0.7 to 0.5, compressive strength increased about 168.2%, 181.9% and 148.0% for each cement type. Compressive strength reduced with decrease in w/c between 0.5 and 0.3. It was attributed to the influence of insufficient mixing and placing of concrete due to lower workability. Superplasticizer was used to improve workability without changing the w/c ratio and significant increases in compressive strength values were observed for w/c of 0.3 about 228.2%, 272.5% and 144.8%. Results showed that cement type has an important role on the compressive strength irrespective of w/c ratio. Compressive strength values of the samples having w/c ratio of 0.5 at the age of 28 days were found to be 26.2, 44.4 and 48.7 MPa for CEMIV, CEMII and CEMI respectively.