Page 28 - PH_Masonry_Final_Ver 1_July 2020

Gap-grading

This is a kind of grading which lacks one or more intermediate size. Gap-graded aggregates can
make good concrete when the required workability is relatively low. When they are used in high
workability mixes, segregation may become a problem.

Uniform Grading

For the uniform grading, only a few sizes dominate the bulk material. With this grading, the aggre-
gates are not effectively packed, and the resulting concrete will be more porous, unless a lot of

paste is employed.

Open Graded

The open graded contains too much small particles.

Impurities in aggregates and its effects on Concrete:

Impure Substances Effects on Concrete
Affects setting and hardening time and may
1) Organic impurities
cause deterioration

2) Materials finer than number Affects bonding and increases water require-
200 sieve ment

3) Coal, lignite, or other light- Affect durability and may cause stains and pop
weight materials outs

4) Soft particles Affects durability

Affects workability and durability and may cause
5) Friable particles
pop outs

Participant Handbook : Masonry 28