Question about the right time to start floating a slab

I've been seeing a lot of guys on my crew start to float way too early lately. They see the bleed water disappear and go for it, but that's a big mistake. I learned this the hard way on a big garage pour in Spokane last fall. We started floating as soon as the surface looked ready, but it was still too wet underneath. The result was a ton of hairline cracks that showed up after a month. My old foreman told me the real test is to step on it lightly; if you leave more than a quarter-inch deep print, it's not ready. Waiting those extra 20 minutes makes all the difference for a strong, crack-free finish. Has anyone else found a good trick to know exactly when the slab is ready for the bull float?

2 comments

2 Comments

emerycarr3d ago

Your old foreman had it right with the boot test. I also check by dragging the edge of my trowel lightly across the surface. If it leaves a clean, sharp line without tearing or pulling up paste, that's my green light. Rushing it just pulls the fines up and weakens the top layer. What mix are you usually working with?

wesley_thompson3d ago

Nah, that trowel test wastes good working time.