Concrete time to cure?

Mike,

I think you should ask the person pouring the pad what you need to do to protect your warranty.

If it were mine I would cover it with plastic and wait at least a week before I added any weight to it. I am pretty sure it takes 30 days or so for concrete to reach it's maximum strength.

Colbyt

Right on.

Design strength is 28 days but it still gets harder over time. You might be able to cheat on the week a little but you are only cheating yourself.

Wow. A week at least, huh? If the SPA does not sit 100% on the concrete; ie. it has some way to let the concrete "breathe", would it reduce the time for set-up?

I guess I just don't understand the process in which concrete hardens. I thought it a chemical process and it cured at the same speed throughout the thickness of the pad. To make matters a bit more complex, the contractor wants to make the back end about 2 foot thick to compensate for grade/elevation.

Thanks!

M. Osborne wrote:

Nope. Concrete cures in a chemical reaction which requires water. It doesn't dry like Elmer's glue...

You need to wait at least a week (ask your contractor), and should also ask your contractor about keeping the pad damp while it cures.

KB

Mike,

As a rule of thumb, concrete will gain half of its final strength in the first three days after it's placed and about 2/3 of final strength in 7 days. I might hold off another day in placing the spa on the new concrete.

Best wishes,

David Alexander

No. it is a chemical reaction and air is not a factor. You want to keep it wet for a couple of days also for best strength

Right, but air and breathing do not help.

That won't hinder the curing time. Check out some information on building Hoover Dam. One huge pour of concrete. Ed

This is Turtle.

i have concrete pads poured for hvac package units that weigh about 3,000 pounds on a 8 foot X 8 foot pad. The fellows that pour the pads and cure them tell me don't mess with it for any time less than a week or you can stress it and it will crack later. Usely it is 2 to 4 weeks before i set the units in place and I have never had one crack yet on 20 years. Now I do use now a days Fibre Glass filled concrete with no rebar in it.

TURTLE

Mike:

In all the discussions with my spa guy, the best way is to set the spa on pea gravel. I have mine on 8x8x16 outer frame with a 28x frame on that, then the fill inside of pea gravel. A solid base allows no room for settling or cradling any uneven surface on the bottom of the spa. It just assumes that the bottom of the spa is perfectly flat and that it is perfectly lined up with the outside base.

This will lead to cracking.

Steve

which still hasnt stopped cooling

randy

Er, no. not even close.

You're paying for this, don't rush it.

I just got a new driveway. We covered it with plastic and, when the sun was beating on it, we hosed it down. After 48 hours, no problem driving a (350lb) motorcycle ACROSS it, but we didn't park the car on it for 2 weeks.

The longer you wait, the longer it will last.

According to the Learning Chalnnel, it's not the Hoover Dam. And the concrete is still curing to this day.

When I was a kid, it was the Hoover Dam. They went and changed it to Boulder Dam. I've been to it and took various tours a few times, but I still never remember if it was Hoover now Boulder or Boulder now Hoover. Either way, it is quite a piece of work. Ed

I'm not an expert in concrete, but I have a comment from personal observation. When concrete is curing, it contracts a very small amount. Grooves are cut in the concrete to accomodate this and the concrete will crack in the grooves instead of the finished surface. Maybe a 10x10 slab wouldn't need one, I don't know. Since this slab is only 5-7 inches thick going to 2 feet in the rear, I would expect some serious cracking to take place later on unless proper precautions are taken. The front where it is

My next door neighbor Paul graded his own driveway and did a lousy job of it. It is 4" thick along the edges, but down the middle it was about 12" thick (a little more in a couple of places). 10 years later there are cracks down the middle so bad that it almost looks like someone tried to take it out at one time. It looks terrible. The contractor he used is the same one that did my driveway, and he told paul that this was no good and almost refused to finish the job. But Paul was fully warned and wanted him to go ahead and do it. My driveway (which adjoins his) is beautiful (if huge slabs of concrete can be beautiful).

But since your slab will all be covered maybe this isn't an issue for you.

By the way, There was a program on Hoover/Boulder dam on the telly a while back. One of the usless pieces of information that I remember from that program is that the concrete will not be fully cured until the year 2060, nearly 130 years after the first concrete was poured on June 6, 1933.

Hi, Concrete lasts forever to cure. It' always curing mode. If I were you, I'd wait a week to 10 days(prefered) before I put a load on it. Tony