In order to determine the effects of coarse aggregate
size on the flexural strength of concrete, concrete beams were produced in
accordance with BS 1881-108 (1983) and American Society for Testing of
Materials (ASTM C293) with varying aggregate sizes 9.0mm, 14mm, 18mm, and 24mm,
using a standard mould of internal dimension of 150 x 150 x 750mm for the
reinforced concrete beam. The water cement ratio was kept at 0.65 with a mix
proportion of 1:2:4. The specimen produced were all subjected to curing in
water for 28days and were all tested to determine the flexural strength using
Universal Testing Machine. The slump tests (Workability) of the concrete
mixtures prepared with each of the aggregate sizes were also conducted. The
results showed that, aggregate sizes of 9.0, 14.0, 18.0 and 24.0mm have slump values
of 101, 120, 158 and 160mm and flexural strengths of 4.91, 4.81, 4.13 and
4.03N/mm². It was concluded that, concrete to be used mostly to resist flexural
stresses should be made of finer coarse aggregates.
