Dry shrinkage or drying shrinkage occurs due to loss of moisture in the concrete. There are different types of water in a hydrated cement paste. Dry shrinkage occurs due to the loss of capillary water.
This water can be found in voids of sizes ranging from 5 nm to 50 nm in the hydrated cement paste. Due to the small size of the voids, the water is held inside by surface tension or capillary tension. Due to the bond created by the surface tension, evaporation, or any other form of removal of this water causes significant volume changes to the structure. This volume changes causes dry shrinkage to the structure.