Must have been the humidity, but my slab went from broom finish to polished smooth in 20 minutes flat.

I'm out in Phoenix last August, finishing a driveway, and this dust storm rolls in out of nowhere. By the time it passed, the surface had this weird sheen like I'd troweled it twice. Has anyone else had weather totally change their finish mid-pour like that?

2 comments

2 Comments

nathan5451mo ago

Oh man, hold on a second! That dust storm probably didn't make it polished - it likely made it feel that way because of all the fine grit that got pressed into the surface. In Phoenix with that heat, concrete sets crazy fast, like 20-30 minutes sometimes. That sheen you saw was probably from the dust particles getting locked into the top layer, not from you overworking it. It sounds like the grit acted almost like a light sanding, giving it a smoother feel, but it also could've sealed in dirt that'll make it look dull and patchy once it's fully cured. I'd hit it with a light acid wash or a pressure washer on low to see if that "polished" look washes off, because if it's just embedded grit, you might lose that sheen and end up with a blotchy mess. Weather can totally mess with a slab, but that smooth look usually means something got trapped in there, not that you troweled it twice.

reese861mo ago

Gotta wonder if that grit is actually acting like a mini sealer though. Like, if the dust was packed in tight enough, it might have filled all the tiny pores in the concrete surface. That could actually make it harder for water or stains to get in later, which some people pay good money for. But then you're stuck with whatever color that dirt was, and that's a gamble. Probably still worth washing it off just to see what you're actually working with underneath.