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Vent: Watching a crew try to finish a slab with the sun already baking it is just painful | Concrete Finishers - The Design Community Hub

the_thea•5mo ago

Vent: Watching a crew try to finish a slab with the sun already baking it is just painful

I saw a crew in Mesa last week start their finishing work at 10:30 AM on a 90-degree day. The concrete was already setting up way too fast, and they were fighting it the whole time. They kept adding water to the surface, which is a total rookie move that just weakens the top layer. I know the schedule is tight, but you have to pour early or wait for a cooler part of the day. Once that crust forms, you're just putting in bad work. I've had to fix too many spider-webbed slabs from this exact mistake. Has anyone else had to convince a foreman to shift a pour time to save the job?

3 comments

3 Comments

victor6365mo ago

Watching them hose it down is like seeing someone try to put out a fire with gasoline. Might look like it's working for two seconds, then you just get a bigger mess. That crew was basically signing the concrete's death certificate with a garden hose. Next week they'll be back out there staring at a map of cracks and blaming the mix.

wadepalmer4mo ago

Ever see what happens when they try to pour a slab on a hot asphalt parking lot? Saw a crew doing a patch job in a grocery store lot last summer. They had the concrete down, but the blacktop underneath was just cooking it. By the time they got around to even thinking about curing, the surface looked like a dried-up riverbed. Alligator cracks within a day. They ended up having to tear the whole section out.

mark_fisher485mo ago

That water on the surface trick is a sure sign of panic setting in. What a lot of crews forget is the heat coming up from the subgrade, not just the sun beating down. If the ground itself is hot from days of baking, it'll suck the life out of that concrete from below before you even start. Sometimes you see them check the air temp but totally ignore the slab temp, which is the real problem. A cheap infrared thermometer could save them a world of hurt, but good luck getting that through to someone who's already behind schedule.