Plastic Shrinkage Cracks

Evaporation of water from fresh concrete is due to the absorption by formwork and during the hydration process. The surface of concrete dries up when the loss of water from the surface of the concrete is faster than the migration of water from the interior to the surface. This creates a moisture gradient which results in surface cracking while the concrete is stiff in a plastic condition. The magnitude of the crack depends upon the rate of evaporation of water from the surface of the concrete.