Civil Engineering - Concrete Technology - Discussion

The aggregate with rounded shape has the minimum percentage of voids ranging from 32 to 33%. It gives the minimum ratio of surface area to given volume and hence requires minimum water for lubrication. It gives good workability for the given amount of water and hence needs less cement for a given water cement ratio. The only disadvantages are that the interlocking between its particles is less and hence the development of bond is poor. This is why rounded aggregate is not suitable for high strength concrete and for pavements subjected to tension.

Workability decreases if the concrete aggregate contain above options bcoz, surface area is high.

Rounded and semi-rounded aggregates increases workability because for a given volume it has less surface and less void, so excess paste is available to give better lubricating effect and rounded aggregates has less friction resistance.

Important nature of workable concrete is its lubricating nature.

Surface area as decreases strength decreases but work ability increases. So round gives more work ability but less strength and flaky elongated material gives less work ability and more strength.

Rounded shape particles are the most suitable for the high work-ability, but Triangular shape of aggregate is best for high strength b/c of good bonding between cement paste and aggregates.

The more the surface are the more cement paste required for enveloping them. So as flaky, elongated particles have more surface area less cement available, less cohesion, more segregation.

Rounded shape particles are the most suitable for the high work-ability, but angular shape of aggregate is best for high strength b/c of good bonding between cement paste and aggregates.

This type of particle lead to reduce work ability because there is formation of voids between them therefore there will not have grip between the concrete constituents.

I think elongated aggregate are more than useful for construction. Because is more than strength and work ability and structure life is many more years.

Rounded shape of the agrt are not suitable for any kind of concrete structure. Because there will not have grip between the concrete constituents.

According to SSC JE CE 2019,

Rounded aggregate : High workability and low strength.

Angular aggregate: Low workability and high strength.