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Curing Concrete.

7K views 16 replies 12 participants last post by  PrimeMover 
#1 ·
I finally got my garage floor poured yesterday. It is 6" thick except around the edges where it goes to 10". Strength is 25MPA.

How long until I can park on it. Everyone I talk to has a different answer ( from today to not for 28 days )

What is a safe amount of time?

Thanks
 
#4 ·
A week would be plenty. The 28 day number comes from the fact that concrete reaches its maximum strengh in that time. It is the spec for critical structures like bridges, & buildings. For a parking slab, especially one that is 6" thick - normal is 4", adequate strength is reached in a couple of days.
 
#8 ·
1 week and wash it off everyday or twice a day if the sun hits it. Keeping it moist lets the concrete cure better. Make sure you have control joints sawed into the concrete also. It will crack so you want control joints so the cracks will follow them instead of going all over the place. How many times have you been out walking around on it trying it on for size?

Kevin
 
#9 ·
My Dad was a cement finisher for 46 years. He always said the perfect cure for concrete is 99 years under water. I think that's overkill. On a six inch slab with wire mesh, I'd keep it wet for a week before I drove onto it. If you can scuff it with your shoe, it's still green - be carful for a few days, it'll cure.

PrimeMover
 
#10 · (Edited)
[email]willys36@aol.com[/email] said:
A week would be plenty. The 28 day number comes from the fact that concrete reaches its maximum strengh in that time. It is the spec for critical structures like bridges, & buildings. For a parking slab, especially one that is 6" thick - normal is 4", adequate strength is reached in a couple of days.
Thanks. Is a normal slab only 4" thick? They must be concrete crazy around here. My bud's neighbour built a garage, dug 6' for the footers and foundation and has a 12" slab.

Kevin45 said:
How many times have you been out walking around on it trying it on for size?

Kevin
I have been out there at least a dozen times today watering and planning where everything will go. I was not allowed to plan for a lift or a pit. Stupid city regs. I have it full all ready ( in my mind at least ) . I wish I could have built it larger.

On the plus side the wife and I are buying an acreage so I will get to do this again. I am planning a 40 by 60 auto shop and a 20 by 30 wood shop.

I was also planning to build a smaller auto shop so I did not have to heat so much in the winter. I spent $300+ per month last winter just keeping the house warm.

PrimeMover said:
My Dad was a cement finisher for 46 years. He always said the perfect cure for concrete is 99 years under water. I think that's overkill. On a six inch slab with wire mesh, I'd keep it wet for a week before I drove onto it. If you can scuff it with your shoe, it's still green - be carful for a few days, it'll cure.

PrimeMover
If it would have kept raining it may have all been underwater.

I did not use mesh opting instead for 10MM rebar at 18 inch intervals. I assume it should be strong enough for the cars I own.
 
#13 ·
Senor...After it is poured and set up you can't keep it too wet. As Primemovers dad stated the perfect cure would be 99 years underwater. The slower it cures the tougher the concrete is. You ever see them pour a sea wall? Put the forms in the water, back the truck or barge up to the forms and pour away. Concrete sea walls last for years and years without deterioration. The best thing you could do is dampen it down and cover it with plastic for awhile, but for the most part just wash it off once or twice a day will do the job. The biggest thing with concrete is make sure you get the expansion joints sawed in to control cracking. Now a SAFETY LESSON...ALWAYS wash off concrete if it gets splashed on you. I was pouring footers for my first garage by myself and the guy running the concrete truck told me to be sure to keep it washed off or I could get concrete poisoning. Never heard of it. I worked around concrete with my dad for years and never had a problem. On concrete guy in town was known as the barefoot concreter. He never heard of it. Well...I got it. When I was pouring the footers, I was down in the concrete. It came up over the top of my boots a couple of times but I didn't think it was anything to be concerned about. I finished up pulled my boots off and my ankles were a little red. Just about like a mild sunburn. I took a shower, washed them off, and they looked a little redder. They were starting to hurt a little so I layed down on the couch. This was on a Sat. By Sun. they were really painful but I figured it would go away with a little ointment on them and some Tylenol. By Monday I couldn't get my shoes on, feet swollen up about 4 times their normal size, couldn't walk at all, and severe pain. Made it to the doctor. He stated do not go back home, go straight to the hospital. I was on antibiotic IV's for 5 days straight, physical therapy for 2 weeks after that to keep the circulation moving, and off work for 2 months. Huge scars on my ankles from the chemical burns and discoloration of the skin. It is something I never ever would want to go thru again. So if ever messing with concrete, use safety precautions and make sure you keep it washed off.

Kevin
 
#16 ·
Prime mover's dad is right. Concrete for testing is poured into round containers. set into water kept at about 42o, 1 week testing as x number of crushing lbs, 28 days for maximun allowed for the test. Mist the concrete, never allow it to "rain" down on the slab. Most jobs I've seen call for cuts every ten ft. or 100 sq. feet. depending on your compaction though, concrete will crack where it dam well wants to..Dan
 
#17 ·
Thanks Dinger. Dear ol' Dad used to lay awake at night worrying about cracks in his concrete. He spent the last 15 years of his career working for a landscape architect doing exposed aggregate patios, pool decks and trick winding step jobs. Most of them either had redwood or brick strips. He was a real genius at his craft, even at 75 years old he could teach the average young buck a thing or two with a trowel and edger.

I built my little shop back in 79. I helped him set up the slab but the Old Man poured it and finished it under a vis-queen tent in the rain by himself, while I was at work. It was a Birthday present. Dad's 87 now, and the garage floor will undoubtedly out last him. If it's any consolation prize, there ain't crack one in it yet. When I finally retire, it'll be easy to let this house go in favor of more space. It'll be hard to part with this little 20-24 garage.
 
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