Effects of Water-Cement Ratio on Compressive Strength of Sprayed cured Concrete

Abstract

Different water cement ratios are usually adopted to produce concrete elements depending on the strength and workability intended to achieve. However, their strengths partly depend on the w/c ratio, degree of compaction, method and duration of curing. The structural or engineering performance of concrete depends largely on its strength, particularly compressive strength and therefore proper attention is needed in the process of hardening of concrete. Preliminary tests were carried out on aggregates and cement to established mix design (British method) and concrete cubes were cast at water-cement ratios ranging between 0.45 and 0.75 and to examine their effects on the compressive strength of concrete. A total of 175 cubes were cast with 25 each for various mix ratios. The cubes were cured using spray curing method in the laboratory at room temperature. The results indicate that the average compressive strength values for 28-day curing varies with water cement ratio. The compressive strength of specimen decreases with increase in water – cement ratio. The water- cement ratio of 0.45 produced the concrete with highest compressive strength of 36.46 N/mm2 at 28 days while 0.75 w/c ratio produced concrete with the least compressive strength of 13.30 N/mm2 at the same curing age. It was concluded that the use of water – cement ratio above 0.60 should be discouraged since it produces concrete with compressive strength below 21 N/mm2 which is the minimum required compressive strength value specified by the National Building Code.