Properties of concrete in plastic & hardened state
A freshly mixed concrete should contain the characteristics given below :-
- Fine workability
- Free from segregation
Workability is described as the easiness for mixing, transporting and positioning concrete in a consistent condition.
Segregation stands for the detachment of course materials from other mass. With the rise in the water quantity in the mix, the bigger sized aggregates are detached and lead to segregation. So, there should be no segregation in concrete.
- Free from bleeding
Bleeding is described as detachment of water or water/sand/cement from freshly mixed concrete. It occurs if there is surplus water in concrete.
Properties of concrete in hardened state
A hardened concrete should contain the following properties :-
- Sufficient strength
- Low shrinkage
- Least thermal expansion
Strength means the defiance of a hardened concrete to crack under various loadings and is commissioned several ways i.e. tensile strength, flexural strength etc. A standard quality concrete in hardened state should contain the optimal crushing strength.
It belongs to the time period up to which the concrete in hardened state resists the impact of weather efficiently. The water cement ratio mainly influences this property. A standard quality concrete in hardened state should be long lasting.
It is described as the characteristic to withstand the entrance of water. This characteristic is obtained with excess quantity of cement in concrete mix. A concrete should be impermeable in harden state.
Since hardened concrete is fragile material, it is necessary that it should contain sufficient elasticity.
There should be minimum shrinkage in hardened concrete. This characteristic is maintained with water cement ratio. Shrinkage is reduced when the water cement ratio is less.
A hardened concrete should contain minimum coefficient of expansion.