Comparative Assessment of Effects of Types of Coarse Aggregate on Strength of Different Grades of Concrete in Imo State, Nigeria

Abstract

Production characteristics and compositions of constituent ingredients of concrete influence to a large extent the quality of concrete works in general. The levels of implication of these factors on performance of concrete are therefore appraised for improved production of concrete work in the study area. Experimental research method was adopted to obtain data on the compressive strength of concrete produced at some construction sites in the study area. A preliminary survey conducted confirmed that 1:2:4 and 1:3:6 mix ratios are commonly used as their mix designs. Forty eight concrete cubes of 150mm x 150mm x 150mm were used to collect sample at the selected sites for the laboratory tests. Product moment correlation coefficient was used to determine the strength of relationship for changes in the increasing strength of concrete with increase in curing ages between concrete produced with sedimentary and granite aggregates. On the other hand, differences in proportion of variation on strength of 1:2:4 and 1:3:6 concrete mix ratios between concrete produced with the various types of aggregates at 7-day and 28-day curing ages respectively were analyzed using Z–test statistics.  Findings reveal that it is only concrete produced with granite material aggregate at the 28-day curing age reached the minimum stipulated standard strength values of 21N/mm2 and 18N/mm2 for 1:2:4 and 1:3:6 concrete mix ratios respectively. The correlation coefficient (r) of 0.999 and 0.993 for 1:2:4 and 1:3:6 concrete mix ratios respectively were calculated to confirm very strong association in changes in strength as the curing age increases between concrete produced with the two different aggregates. The difference in proportion of the variations in the two different mix ratios between the two different aggregates at the curing ages however are not significant in the study. Thus, the study concludes that mix ratio and curing age which remain positively strong on their effects on quality of concrete are as well significant as aggregate type in the overall performance of concrete. Granite material aggregate therefore was recommended to be used for concrete production of higher quality; and as well be always cured till the 28th day of production for desired strength of the concrete.