Abstract:
Concrete is one of the commonly used construction materials throughout the world. Concrete
is essentially a mix of coarse aggregate, fine aggregate and cementing materials. ACI method
of concrete mix design is one of the widely used methods for proportioning quantity of coarse
aggregate, fine aggregate and cementing materials in concrete. According to ACI method of
mix design, the volume of coarse aggregate requires to proportion per unit volume of concrete
depends on the size of the coarse aggregate and the fine aggregate gradation, expressed in terms
of fineness modulus. But the strength and durability of concrete depends on aggregate size
distribution (gradation) rather than maximum size of aggregate. In this thesis effects of coarse
aggregate size on compressive strength of concrete are examined. The maximum sizes of coarse
aggregate are chosen as 3/4 and 3/8 inch for mix design. The design strength of concrete is
assumed 3000 psi and water cement ratio of 0.68 on the basis of design strength. The concrete
is also assumed non-air-entrained type. The workability of concrete expressed as slump istaken
1-2 inch. The fine aggregate used in this experiment has fineness modulus of 2.5. Ordinary
Portland cement is used as cementing material. Two sets of concrete cylinder are prepared with
ACI mix design ratios and tested at 28 days. The average compressive strength of 3/4 inch and
3/8 inch aggregates are found 2471 psi and 2518 psi respectively. Experimental results have
revealed that, maximum sizes of coarse aggregate have very little effects on compressive
strength of concrete.
