Old timer told me to wet the forms before pouring and I brushed him off

Guy named Jerry on a job in Phoenix last summer kept saying spray the forms down, I thought it was a waste of time. Well, next day we had a 40 foot stretch of sidewalk that cracked like a dry lake bed because the wood sucked all the moisture out. Has anyone else had a simple tip like that turn out to be the difference between a good pour and a redo?

2 comments

2 Comments

leor373d ago

Oh man, I gotta push back on that a little. Wetting the forms is important, but if your whole sidewalk cracked overnight, you probably had bigger issues than dry wood. Like, was the mix right? Did you cure it at all? I've seen guys soak the crap out of plywood and still get cracks because they poured in direct sun with no fogging or wet burlap. That old timer gave you good advice, but don't blame the form moisture for a 40 foot crack. That sounds like a water/cement ratio problem or bad finishing timing to me.

baker.phoenix2d ago

Are you sure that cracking had nothing to do with the forms sucking the water out? Wood is like a sponge especially in Phoenix where it's bone dry. If those forms pulled enough moisture from the bottom and edges of the slab, that concrete would set up uneven and weak right there. I've seen it happen where the middle of a pour looks fine but the edges near dry plywood turn into a mess of hairline cracks overnight. That's not a mix issue, that's the wood robbing the concrete of the water it needed to hydrate properly. Curing matters but if the damage is done in the first few hours, no amount of wet burlap is going to fix it. The old timer knew what he was talking about and Jerry learned it the hard way.