Concrete Shrinkage – Shrinkage of Concrete

Concrete shrinks during setting and drying due to hydration of cement and produces shrinkage cracks. The drying shrinkage increases with an increase in cement content or an increase in water content. Shrinkage is greater with richer mixes (more of cement) and also with aluminious cements. Other things being equal, shrinkage of concrete is almost directly proportional to the amount of-:water in the mix. The type of aggregate used does not generally affect the shrinkage seriously though it has an indirect effect due to the difference of water/cement ratio depending on the type of the aggregate ; with large size of aggregate shrinkage is low. Where shrinkage may give rise to high tensile stresses such as in road slabs, lean dry mixes are desirable. Rich mixtures are uneconomical and are used only for impermeable constructions to ensure water-tightness.