Slab started cracking 20 minutes after I finished the broom finish - here's what I think happened

Working a driveway in Phoenix last Tuesday. 95 degrees, low humidity. I poured, finished, and the surface was setting fine. Then I heard it. A hairline crack running right down the middle, about 8 feet long. I think I waited too long to cut control joints. Did my timing, since the mix was a 3/4 inch slump and I thought I had more working time. Ended up having to saw-cut a joint over the crack and hope it looks decent. Anyone else run into this in hot weather and have a trick for catching it before it starts?

2 comments

2 Comments

claireo673d ago

Saw this at my last job too, hot weather always makes concrete set faster than you'd expect. Kind of like how a hot pan cooks the outside of food before the inside is done, moisture leaves the surface way quicker than the core.

quinn_king162d ago

Came here to say the same thing... hot weather messes with concrete in weird ways. The surface dries out way too fast while the middle stays wet. Gotta spray it down or cover it up to keep it even.