Craze cracks only penetrate the top skin and outline small cells, usually less than 2 in across, most visible as a wetted surface dries. They come from rapid surface drying, finishing with bleed water present, dusting cement onto wet spots, overtroweling or late curing. Crazing is cosmetic and rarely spreads, but it tells the owner exactly how the slab was finished.
That's crazing, not structural, but it's what you get when they troweled the bleed water back in.
Also heard as
- craze cracks
- checking
- hairline cracking
Do not mix it up with
- ASR: ASR also leaves a map pattern, but its cracks are deeper, wider and often edged with gel or staining.
Related terms
Bleed water
Water that rises to the surface of fresh concrete as the heavier solids settle.
Plastic shrinkage cracking
Cracks that open in fresh concrete before it sets, when the surface dries faster than bleed water replaces it.
Curing
Keeping fresh concrete moist and warm enough, for long enough, that the cement keeps hydrating.
Laitance
The soft, chalky skin of fines that bleed water leaves on top of concrete, too weak to bond to.