curing concrete / car lift

[Pcoghlan]

So, I laid a six inch concrete slab four weeks ago and 90% of it has dried to the point it is now an off-white. There are still some small patches of dark grey etc which I suspect to be places where it is still moist or uncured?

Anyway, I picked up my Atlas OH9000 last week and have it sitting on car dollies, awaiting installation.

The thing is this, whilst I laid the bulk of the slab at six inches, I dug deeper for 10-12 inch footers for the two lift columns. As such I am considering whether I should leave it another month before installing.

Anyone been here and if so did you get any recommendations as to the delay before installation when having deeper than usual footers?

The photos here despite the fairly awful focus do give you an idea as to what I mean...

Paul

 

[47p2]

I left mine 6 months to cure before installing my lift

 

[bop_pa]

My understanding is it takes concrete 28 days to cure. After pouring it is a good idea to keep it hydrated and the water will help the chemical reaction and produce a higher strength end product. It only takes a little misting to work.

 

[Beytill]

Concrete is at its full tensile strength at 28 days.

 

[White04mach]

What kinda of Model A you have there....30-31 I see....

 

[Pinhook]

4 weeks?

Put that lift up.

 

[stingry]

So, I laid a six inch concrete slab four weeks ago and 90% of it has dried to the point it is now an off-white. There are still some small patches of dark grey etc which I suspect to be places where it is still moist or uncured?

Paul

What you see is pretty much what you get! The cement is cured by now and for some reason there is that difference in coloration, Mine looks the same way!

Cheers
Steve

 

[ConCretin]

Concrete typically reaches 70% strength in 7 days in test cylinders - slightly longer in place.

 

[rsanter]

concrete actually will continue to cure for many many years to come
if I recall you get something like 95% to 98% of final strenth in one month
the remainder you get slowly over the next 10-20 years

bob

 

[Bob C]

concrete actually will continue to cure for many many years to come
if I recall you get something like 95% to 98% of final strenth in one month
the remainder you get slowly over the next 10-20 years

bob

This is correct. Hoover Dam will take 600 years to cure 100%.

 

[6768rogues]

The design strength is typically reached in 28 days. It will continue to get stronger for a long period of time, but the design has been reached at 28 days (theoretically, that is. The only way to know for sure is to have it tested).

 

[tcianci]

The answers above are kinda right. The concrete will reach its rated COMPRESSIVE strength in about 28 days. In your case go ahead and put up your lift.

 

[Pcoghlan]

Thanks a million everyone. To the person that asked, the Model A is a '30.

I thought maybe deeper concrete would take longer but sounds like I will be busy this coming weekend!

 

[superdutymike27]

concrete actually will continue to cure for many many years to come
if I recall you get something like 95% to 98% of final strenth in one month
the remainder you get slowly over the next 10-20 years

bob

What Bob said.

Concrete is alway's curing. Typically you take 3 cylinder tests and break them at 7, 14 or 21 day's and 28. Most engineer's will allow structural items to commence when concrete reaches 75%. This will depend on what the mix is designed for. If you are concerned, call a structural engineer to advise you on what you next step would be.

If it was me, I would wait another 8 weeks before the install. Remember, it's you, loved one or a friend getting underneath whatever you are lifting.

Just my 2 cents.

Good luck.

 

[Pcoghlan]

Safety being what it is, I think I will let this sit another month or two. I am in no rush. Might focus on building a work bench and trying to shortlist means of insulation for the walls. Maybe get the lift assembled and ready for installation in time for Christmas.

Again, thanks everyone.

 

[BWS]

Engineering and testing tell us 28 days(which is part of the "27 rule" in concrete world)......

I'll tell you the concrete is still "plastic",WRT point loading long after that.IOWs,yes 28 days if the load goin on top of it is spread out.Try putting a huge azz load on it....say a 12" steel column,throw a few too many tons of weight on it and come back in 6 months.

Concrete is like rubber,its very plastic.You've waited prolly long enough to install your lift.......but I'd still "break it in" gently.

 

[78Bird]

Install it, but maybe give it another couple weeks before USING it.

 

[dennis111]

Install it, but maybe give it another couple weeks before USING it.

This +1

 

[Pcoghlan]

Don't know of how much use this is but an update in the event it is indeed useful in the future. I left the slab 30 days before installing the lift AND another 15-20 before actually using it. The lift has performed flawlessly, happy camper.

Paul