# Concrete and its properties

Properties of concrete mainly depend on the blending ratio of cement, sand, aggregates and water. The proportions of these materials, manage the following different concrete properties:

? Grades (M20, M25, M30 etc.)

? Compressive strength

? Characteristic Strength

? Tensile strength

? Durability

? Creep

? Shrinkage

? Unit weight

? Modular Ratio

? Poisson?s ratio

**Grades of concrete**: Concrete is recognized with its grade that is specified as M15, M20 etc. Here M signifies concrete mix and number 15, 20 indicates the stated compressive strength (fck) of 150mm cube at 28 days, provided by N/mm2. So, concrete is recognized with its compressive strength. M20 and M25 are considered as the general grades of concrete. The higher grades of concrete are applied for severe, very severe and extreme environments.

**Compressive strength of concrete**: It has similarity with load. The strength of the concrete differ significantly for the similar concrete mix. So, a single representative value called characteristic strength is applied.

**Characteristic strength of concrete**: It is settled as the value of the strength below which not more then 5% of the test results are estimated to decrease (i.e. there is 95% possibility of obtaining this value only 5% of not obtaining the same)

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