Crazing refers to random, intersecting cracks that extend below the surface of hardened concrete caused by shrinking of the drying surface. This happens because the surface is restrained by the concrete below it that isn’t experiencing shrinkage. Craze cracks can be fine and barely visible to open and well defined. They do not affect the structural integrity of the concrete. Also these cracks rarely affect the durability or wear resistance of the concrete.  Some causes for crazing might be: concrete not properly cured and protected, concrete exposed to fast or prolonged surface drying due to low humidity, high temp; direct sunlight; and drying winds, excess floating which can depress the coarse aggregate resulting in too much paste at the surface, hand trowel finished surface which doesn’t contain a surface hardener, broadcasting cement on the surface to attempt to dry bleed water, using calcium chloride in hot dry weather. Below are some ways to reduce the likelihood of such problems:

-Start curing as soon as possible. Wet curing keeping surface continuously saturated are most effective

-Do not cure concrete intermittingly

-Don’t broadcast cement to the surface to try to eliminate bleeding. Always order specified slump and use admixtures like water reducers to help eliminate bleeding

-Utilize evaporation retardant or fog spraying prior to curing to retain surface moisture