Debate: is 50 psi the magic number for air entrained slabs or does it depend?

I hit a slab last month where 50 psi air content gave me no freeze-thaw issues but the surface finish was rough. My old boss swears by 50 psi on everything, but I'm starting to think it's a range thing. What's your go-to number and why?

3 comments

3 Comments

xenaf5124d ago

You got me thinking about a job I did near Buffalo last winter. We ran air content at 55 psi on a warehouse floor and that surface was like sandpaper, no freeze damage though. My old foreman swore by 45 psi and said the extra air just messes with the finish, and I think he was right for some mixes. It really depends on the aggregate and how tight the mix is, not just a one size fits all number. I feel your pain on that rough finish, it's frustrating when the numbers look right but the slab doesn't cooperate.

blair_webb24d ago

Yeah no kidding, had a buddy who swore by spit and a prayer instead of a gauge.

faith_king24d ago

Right? That rough finish is the worst. It's like you hit your numbers but the slab looks like a gravel road. Totally feel you on that. I think that 50 psi is more of a starting point than a rule. The mix design and the weather the day you pour change everything. My old boss was the same way, swore by 50 no matter what, but he'd get away with it cause his aggregates were always super consistent. Not everyone has that luxury.