Rant: My foreman swears by a 3 inch slump for driveways, but the old guy at the supply yard told me that's way too wet.

We were pouring a driveway in Boise last Thursday and the truck driver said he'd seen crews use a 5 inch slump for the same mix. My foreman says a wetter mix finishes faster and smoother, but the yard guy argued it leads to more cracking and lower strength. I'm stuck in the middle on this one. What slump do you all aim for on a standard residential driveway pour?

3 comments

3 Comments

kim_martin22d ago

Man, being stuck in the middle of the foreman and the yard guy is the worst spot! I've totally been there, trying to smile and nod while two guys with way more experience argue over the chute. For a driveway, I'm usually aiming for a 4 inch slump. It's a good middle ground that's workable but not so wet it bleeds all over. That 5 inch slump the driver mentioned sounds like soup to me, way too easy to mess up the finish.

foster.mary17d agoTop Commenter

But how do you even measure slump on site without the cone, just eyeball it?

maxburns22d ago

Yeah, that 4 inch middle ground is the sweet spot for a reason. It gives you enough time to work it without watching all the cream rise to the top. A 3 inch slump can fight you on a hot day, and a 5 inch is basically admitting you forgot to order a vibrator. The old guy at the yard is right about the cracks, a soupy mix shrinks way more as it dries.