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Rick, General Contractor
Category: Home Improvement
Satisfied Customers: 21386
Experience:  Licensed construction supervisor with 35+ yrs. experience.
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my contractor poured the slab andfoundation for our new home

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my contractor poured the slab andfoundation for our new home and then within 24 hours was using a forklift to stack cement blocks on it in preparation for the walls and framing. Was that enough time for the concrete to cure before placing that kind of weight on it?
I will do my best to help you with your issue

You are justified in your concern since it takes at least a week for any significant curing to take place. But if there is no damage to the slab showing then you sholu be ok. Unfortunately it may take a month (it takes 4 weeks for an ~80%+ cure) to tell. Your only recourse, it would seem, would be to hold back a significant chunk of money until you're sure there is no problem with the slab. There is a good chance you'll be ok and unless this contractor is a total newbie I expect he's probably done this before with no big problems.
Customer: replied 4 years ago.
Thanks for your reply. The builder is not a newbie. It's Adams homes in Florida.they are a good sized regional builder. This is in a development they are doing. There is no visible damage to the slab but what I'm afraid of maybe a deep crack that will come back to haunt us down the road with cracked stucco or doors and windows that don't close properly after a year or two. So, from your reply I take it that it's not a 100% chance that putting weight on it will damage it but it increases the chances. Also I'm assuming they should and will wait at least three days before actually beginning to put cement blck walls up and the roof trusses which will add considerable strain to the foundation and slab. They used fiber mesh concrete with a monolithic pour if that helps you refine your answer at all.

If the site was properly prepared and the pour was on undisturbed or properly compacted soil then chances you'll have a problem are small. Using fibers in the pour minimizes the chances of cracks forming. Given you have an experienced contractor I wouldn't be too concerned but I would pay close attention to what happens for the next several weeks. After that, if nothing shows, you should be fine. Preparing the site is much more important for preventing cracks than the time of the cure since this pour is entirely supported by the ground.

Customer: replied 4 years ago.

ok. what should I look for as signs of trouble? hairline cracks? cracks in certain locations? size of cracks?

Yes cracks of any kind. But only significant cracks are a cause for concern. Hair lines are more indicative of too rapid air curing than structural issues. The cracks would show where there is a load (weight) on the slab. But this would be more indicative of improper site prep than prematurely loading a not sufficiently cured slab.
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