Richie I. Umasabor & Effort O. Osayogie
This paper examined the effect of coarse aggregate sizes on the compressive strength of concrete using response surface methodology. It has become imperative to carry out this study to ascertain which aggregate size, will produce the optimum compressive strength, which may guide engineers when using it in the construction industry. Regression equations relating the compressive strength of concrete using various aggregate sizes with both the curing duration, fine aggregate, cement and water/cement ratios were developed. The adequacy of the model was checked using the coefficient of determination (R2 ). The results showed that the 9.5 mm aggregate sized concrete had 35 N/mm2 as compressive strength for 28 days curing duration, while the 12.5 mm aggregate sized concrete had 24 N/mm2 as compressive strength for 28 days curing duration and the 19 mm aggregate sized concrete’s compressive strength was 23 N/mm2 when cured for 28 days. The compressive strength of 9.5 mm aggregate sized concrete had an increase of 1.46% and 1.52% over the 12.5 mm and 19 mm aggregate sized concrete’s compressive strength. The low coefficient of determination (R2 ) of 0.1270 for 9.5 mm aggregate sized concrete, R2 of 0.1322 for 12.5 mm aggregate sized concrete and R2 of 0.1243 for 19 mm aggregate sized concrete shows that the linear model could not predict the compressive strengths of the different aggregate sized concrete efficiently. Read full PDF
Keywords: compressive strength, aggregate sizes, regression, coefficient of determination
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