Why does nobody talk about the slump test being useless on hot days

I read on a ACI forum that slump tests can be off by 2 inches when the concrete hits 90 degrees because the water evaporates before you even finish testing. My crew in Phoenix avoids it but my partner in Seattle swears by it every pour. Anyone else dump the slump test in summer or still use it?

2 comments

2 Comments

anderson.gavin25d ago

Honestly, the real issue isn't the concrete temperature but the humidity. Bone dry air in Phoenix sucks water out way faster than Seattle's damp air, so the slump drop is more about your local climate than the actual mix. Tbh, who cares about the slump if the load shows up stiff and you just add water on site anyway, that's where the real problems start.

zara44725d ago

Last summer in Texas we had a 103 degree day and I watched the slump drop from 4 inches to barely 1.5 before the truck even pulled away from the chute. We started doing a quick water check by just eyeballing the mix and pressing a handful together to feel the moisture instead of wasting time with the cone. Made a world of difference because we caught the problem before it hit the forms instead of fighting a slump test that lied to us.