What describes the occurrence of fine hair cracks in a newly hardened slab?

Crazing is a term used to describe the formation of fine hair cracks on the surface of a newly hardened concrete slab. These cracks are typically very small and shallow, often appearing in a network or pattern, which can be distinct and visible. Crazing usually occurs due to the rapid evaporation of moisture from the surface of the concrete, particularly in hot and windy conditions, or due to restraining stresses within the slab as it cures.

The presence of fine hair cracks from crazing does not lead to structural damage but indicates that the surface may be weakened or that the curing process was not properly managed. Proper curing methods, including using curing compounds or maintaining moist conditions, can help to minimize the occurrence of crazing.

The other options represent different phenomena associated with concrete. Scaling refers to the flaking or peeling of the concrete surface, often due to freeze-thaw cycles or de-icing chemicals. Dusting involves the formation of fine powdery material on the surface of the concrete, usually caused by inadequate hardening and the presence of unbonded cement particles. Jointing is a method used to control cracking by creating intentional separations in the concrete. Each of these terms describes distinct issues that are separate from the fine hair cracks associated with craz