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Evaluation of the Effects of Nigerian Portland-Limestone Cement Grades on the Strength of Concrete

The influence of Nigerian Portland-Limestone cement grades on the strength of concrete was investigated in this study. Three cement grades of 32.5R, 42.5R and 42.5N were adopted. A constant mix design ratio of 1:2:4 with a varying water-cement ratio of 0.4, 0.5, and 0.6 was used. All of the constituents of concrete were calculated using the mass of a concrete cube specimen of 150mm x 150mm x 150mm. A total of 135 cube specimens were cast and cured for 3, 7, 14, 21 and 28 days accordingly in order to determine the compressive strength of the concrete. The results obtained show that concrete cube specimens produced with Portland-Limestone cement grade 42.5N had the optimum compressive strength on the 28th day of curing in each water-cement ratio. However, the optimum compressive strength on the 7th day of curing in each water-cement ratio was obtained in the concrete cube specimens produced with Portland-Limestone cement grade 42.5R. The results also show that concrete produced from cement grade 32.5 will generally produce more workable but weaker concrete than concrete produced from cement grade 42.5, irrespective of the water-cement ratio. Finally, it was concluded that the compressive strength of concrete is inversely proportional to all the water-cement ratios used in this study, irrespective of the grade of cement.