The compressive strength of concrete is one of the most important and useful properties of concrete. In most structural applications concrete is employed primarily to resist compressive stresses. In most structural applications concrete is employed primarily to resist compressive stresses. In those cases where strength in tension or in shear is of primary importance, the compressive strength is frequently used as a measure of these properties.

The compressive strength of concrete is generally determined by testing cubes or cylinders made in laboratory or field or cores drilled from hardened concrete at site.

Strength of concrete is its resistance to rupture; It may be measured in a number of ways, such as Strength in compression, in tension, in shear or in flexure. All these indicate strength with Reference to a particular method of testing. When concrete fails under a compressive load the failure is essentially a mixture of crushing and shear failure.

The strength that may be developed by workable , properly placed mixture of cement, aggregate and water is influenced by:

·         Ratio of cement to mixing water

·         Ratio of cement to aggregate

·         Grading, surface texture, shape, strength and stiffness of aggregate particles

·         Maximum size of aggregate