The characteristic compressive strength of concrete is determined by performing cube tests and they are performed utilising concrete specimens of a cubical mould of size 15 cm x 15 cm x 15 cm and the cylindrical form of dimension 15 cm in diameter x 30 cm in height.
The compressive strength test of the concrete cylindrical specimen is 0.8 times the strength of cube.
Concrete compression test of specimens is done after 28 days of curing.
With the increase in age, the strength of concrete will increase.
concrete compressive strength at any age = Strength at 28 days x age factor.
Age factors at different age of concrete
concrete Compressive strength of M 25 grade of concrete at 28 days in 25 N/mm2.
So concrete compressive strength of M 25 grade concrete at 7 days = 0.7 x 25= 17.5 N/mm2.
Note: By using High Alumina cement concrete, the strength of concrete will not increase with time.
Properties of Reinforcement Cement Concrete
Apart from the concrete compressive strength, given below other properties of reinforcement concrete which are related to the compressive strength of concrete.
Tensile strength of concrete
Creep of concrete
Durability of concrete
1. Tensile strength of concrete
Tensile strength of concrete is determined by using the characteristic compressive strength of concrete.
ft = 0.7 x square root of fck.
2. Elastic Deformation
The modulus of elasticity is principally controlled by the elastic properties of the aggregate and to a more secondary by mix proportions, the conditions of curing, the type of cement, age of the concrete.