Effect of Coarse Aggregate Sizes on the Compressive Strength of Concrete using Response Surface Methodology

Abstract

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.