EVALUATING THE COMPRESSIVE STRENGTH OF CONCRETE MADE WITH DIFFERENT GRADES OF CEMENT AND MIX PROPORTIONS

ABSTRACT The compressive strength of concrete is a very important factor in design of concrete structures. Various grades of cement are available in the Nigerian market. In this study, the influence of Portland-Limestone cement grades and mix proportions on the compressive strength of concrete was investigated. Two cement grades of 32.5R and 42.5R were adopted. Mix design ratios of 1:2:4 and 1:1.41:2.28 with a varying water-cement ratio of 0.33 and 0.5 were used with addition of superplasticizers. 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 36 cube specimens were cast and cured for 7 and 28 days accordingly in order to determine the compressive strength of the concrete. The results obtained showed that concrete cube specimens produced with Portland Limestone cement grade 42.5R had the optimum compressive strength on the 7th and 28th day of curing in each mix proportions. The results also showed that concrete produced from cement grade 32.5R in each mix proportion generally produced more workable but weaker concrete than concrete produced from cement grade 42.5, irrespective of the water-cement ratio and superplasticizers added. It was also observed that it was possible to produce concrete with compressive strength in excess of 40MPa, using a 1:2:4 mix proportion and 0.33 water/cement ratio. Finally, it was concluded that the compressive strength of concrete is directly proportional to the grade of cement and mix proportions.