Effect of properties of coarse aggregates on compressive strength of concrete.
i. Size of aggregate: If coarse aggregate particles are of large size (say 20 mm) in concrete mixture , then concrete becomes harsh and only strength may reduce due to honey combing. But if coarse aggregate are of smaller sizes only (say 10 mm). Then ultimate strength of concrete will be lesser. Therefore coarse aggregate with combination of both sizes (i.e. 10 and 20 mm) will give better workable concrete and more compressive strength.
ii. Shape of aggregate: If shape of concrete aggregate is angular then there is good interlocking of aggregate particles. Hence it gives more compressive strength. If shape of coarse aggregate is sub angular or sub rounded then compressive strength reduces due to less bonding between particles.
iii. Surface texture: If the texture of coarse aggregate is rough then aggregate gets interlocked strongly than smooth textured aggregates in presence of same cement slurry.
iv. Water absorption: If the % water absorption of coarse aggregate is more than prescribed limit, then concrete becomes harsh result in reduction of strength. But if water absorption is less concrete becomes as per proportion giving required strength.