Shape of Aggregate – Rounded, Angular, Flaky, Elongated

• Rounded – minimum voids, require minimum cement but poor interlocking and bonding.
• Angular – Higher voids, require more cement, but best interlocking and bonding.
• Flaky: Aggregates having its least dimension less than 0.6 times its mean dimension. It has poor bonding and has adverse effect on homogeneity of mix and its strength.
• Elongated: Aggregates having its larger dimension greater than 1.8 times its mean dimension. It has poor bonding and not considered suitable for medium to high strength concrete

Size of Aggregate – Fine, Medium and Coarse

• Fine
• Medium
• Coarse

The maximum size aggregate gives the lower surface area for the development of gel bonds which is responsible for the low strength concrete. Also, non-uniformity in concrete.

Large Aggregate – Lean Mix – High Strength

Smaller Aggregate – Rich Mix –High Strength