Concrete is solid material but it is heterogeneous material and its microstructure varies with time and environmental factors. Properties of any material depend upon its internal microstructure and can be modify by changing its microstructure. Variation in the microstructure affects the mechanical properties of concrete. The most important and basic property of concrete that is kept in mind by concrete technologist and researchers is its compressive strength. There are many factors that affect the compressive strength e.g. temperature during casting, humidity, curing conditions, w/c ratio and admixtures etc.