My foreman in Phoenix said to never use a magnesium float on a slab that's already starting to set up hard, but I tried it on a 90-degree day and it actually saved the finish.

He always said it would tear the surface, but when the concrete on a driveway pour last month started going off way faster than expected, I grabbed my mag float out of desperation and it gave me just enough time to close up the last few trowel marks before it locked up completely, so has anyone else found a time when the 'never do this' rule was wrong?

3 comments

3 Comments

carter.julia1mo ago

Forget the rules and watch the concrete. I've seen guys save a pour by breaking the book because they were reading the slab, not the manual. Sometimes the material tells you what it needs.

derekp701mo ago

Used to be a real stickler for the specs on every job. Then I watched an old timer ignore the plan and add more water on a hot day, just going by how the mix looked in the truck. That pour set up perfect. You're right, @carter.julia, the book doesn't always know best. Got to pay attention to what's right in front of you.

rosejackson1mo ago

That Phoenix foreman gave you a golden rule for a reason. I saw a crew in Tucson try that exact move on a hot deck and it left a ragged surface you could feel with your feet. The old specs exist because a thousand guys before us already made those mistakes. Watching the concrete is good, but ignoring basic trade knowledge is how you get a call-back for a bad finish.