Got a weird finish on a garage slab in Phoenix using a new magnesium float

We were closing up a 30x40 garage floor and I grabbed a brand new magnesium float instead of my usual aluminum one. The mix was a bit wetter than I like, maybe a 5 inch slump. The magnesium just seemed to drag and pull at the surface, leaving these faint, almost wavy lines instead of a tight finish. I had to go over it twice with a steel trowel to fix it. Has anyone else had this happen with a new magnesium float on a wetter pour?

3 comments

3 Comments

bettykim22d ago

Wait, a FIVE inch slump in Phoenix? Bro, that mix must've been soup. No wonder it dragged.

grantl9411h ago

You know what nobody's asking, what was the actual air temp that day? A five inch slump in Phoenix could be anything from a manageable morning pour to pure soup if it hit 110 by noon. That extra heat changes how fast you lose that bleed water, maybe making the magnesium drag feel worse than it should. Timing everything around the sun might be the real problem here, not just the tools.

jakep2423d ago

Man, I gotta disagree on this one. A new magnesium float on a wet slab is a classic move, not a problem. That drag you felt is normal, it's just the tool biting in. Those wavy lines? That's you closing the surface up. Going over it twice with a steel right after might have actually sealed in too much water. On a 5-inch slump, I'd let that magnesium work sit for a good while longer, let the bleed water come up and vanish, then hit it with the steel. You might have been fighting the finish instead of working with it.