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qoncept 04-29-2010 03:44 PM

Pouring concrete with standing water
 
We're getting ready to pour my concrete driveway this Saturday and the forecast is calling for thunderstorms through Friday night. We finished grading last night and brought the end of the driveway where it meets the street up, but before that it was already prone to collecting water and it's still the lowest point of the driveway. Depending on the storm, I'm guessing I could have as much as an inch or two of standing water when we come out Saturday morning.

What do I need to do? I drained most of the water from last weekend's storm out with an old sump pump, but it still left some sizeable puddles. It's of course more or less flat now but it's not going to have anywhere to drain to and the ground is saturated below the new fill. I read somewhere that a using a shop vac to pull some more out is a good idea, but to what extent to I need to dry it out?

Willie T 04-29-2010 04:11 PM

Quote:

Originally Posted by qoncept (Post 435426)
We're getting ready to pour my concrete driveway this Saturday and the forecast is calling for thunderstorms through Friday night. We finished grading last night and brought the end of the driveway where it meets the street up, but before that it was already prone to collecting water and it's still the lowest point of the driveway. Depending on the storm, I'm guessing I could have as much as an inch or two of standing water when we come out Saturday morning.

What do I need to do? I drained most of the water from last weekend's storm out with an old sump pump, but it still left some sizeable puddles. It's of course more or less flat now but it's not going to have anywhere to drain to and the ground is saturated below the new fill. I read somewhere that a using a shop vac to pull some more out is a good idea, but to what extent to I need to dry it out?

What does the bolded part mean? Your whole driveway should be 4" or more deep. And where it meets the road, it should be at least 7" deep, and reinforced with a piece of rebar running across the end. You didn't make this part shallow, did you?

For the most part, new concrete will force puddled, standing water up, over the forms, and out of your life if you provide a place for it to go. (dig some lower holes outside the forms.)

Daniel Holzman 04-29-2010 04:35 PM

If you want your concrete job to last, it is critical that the concrete be placed on freely draining material. Typically that means at least 6 inches of freely draining gravel or crushed stone, or at least coarse sand. If you have standing water, that means the subgrade is not draining properly, and you are placing concrete on poor subgrade. You should at least consider removing the poorly draining subgrade and replacing with free draining material to at least six inches depth.

Willie T 04-29-2010 04:41 PM

Quote:

Originally Posted by Daniel Holzman (Post 435453)
If you want your concrete job to last, it is critical that the concrete be placed on freely draining material. Typically that means at least 6 inches of freely draining gravel or crushed stone, or at least coarse sand. If you have standing water, that means the subgrade is not draining properly, and you are placing concrete on poor subgrade. You should at least consider removing the poorly draining subgrade and replacing with free draining material to at least six inches depth.

Sorry. I should have also covered that. My bad! Here in sunny Florida, 99.9% of our building is done on beautiful sand (great drainage and super compaction), so it kind of slipped my mind.

qoncept 04-30-2010 08:23 AM

Quote:

Originally Posted by Willie T (Post 435439)
What does the bolded part mean?

Guess that was a little ambiguous ... My neighbor dug out the old gravel with his skid loader last week and it was WAY low at that end of the driveway, so we moved some of the gravel back to fill it in. It's about 6" below the form. I'll pick up some rebar tonight on the way home for it. The rest all has wire.

The gravel driveway is 30 years old and as deep as we dug, I never found anything but hard packed gravel. It should drain reasonably well, there is standing water because we've had heavy storms a few days last week and the ground is pretty well saturated. It was all soaked up by the time I got home from work yesterday. About a foot below it's current grade is a gas line (I dug in the grass to the side of the driveway to see how deep it was).

tpolk 04-30-2010 09:59 AM

I would'nt be pouring on a wet subgrade. can you cover?

qoncept 04-30-2010 10:15 AM

Wow, duh.. I have a ton of plastic I can cover it with. Hopefully I can get home before the rain starts. Thanks for knocking some sense in to me. :)

Bondo 04-30-2010 05:59 PM

Quote:

Originally Posted by Daniel Holzman (Post 435453)
If you want your concrete job to last, it is critical that the concrete be placed on freely draining material. Typically that means at least 6 inches of freely draining gravel or crushed stone, or at least coarse sand. If you have standing water, that means the subgrade is not draining properly, and you are placing concrete on poor subgrade. You should at least consider removing the poorly draining subgrade and replacing with free draining material to at least six inches depth.

Ayuh,... I'm havin' a hard time gettin' my head around this,...:huh:

I build driveways, parking lots,+ roads for a living,... In Clay country...
I understand a good base of crushed stone,...
A Normal driveway gets 8" to 12" of crushed rock for support... More for nasty clay areas...
In those areas, We drop in marify paper to block the mud/ clay/ water, then a foot or more of crushed rock...
At this point, it's Boxed out,+ ready for concrete, or asphalt...
If it Rains,... The Box fills up...
It's the Finish Grade, not the sub-grade that does the draining...

Standing water in a boxed out concrete hole is Normal,...
Get out what you can get Out, then pour...
Any remaining water is displaced by the concrete,+ does No damage...
'ell,... We pour concrete Underwater regularly along the river...
Pump out what ya can from the steel piling,+ Pour....
Any excess runs out the lowest point of the forming....

I'd be more concerned about getting it finished,+ Covered, if you're expecting Rain on the day of the pour....
Rain will wash the finish off the top...
Which, I guess is Fine,.. if you're lookin' for the "Exposed Aggregate" look...

jomama45 04-30-2010 07:27 PM

I agree with you Bondo, happens to us all the time. All of the rain from the entire driveway, & inevitably each side of the lawn, runs to the end & stands until it can slowly run away.

In the past when knowing we had a big rain coming, we've feathered & compacted additional gravel at the very end so that the water will drain into the street. If you don't compact though, it will probably turn to mush (dependign on the type of gravel) and not allow you to pour the next day. Obviously, you need to dig the excess gravel out in the morning to pour. And if the driveway is fairly flat, w/o much pitch at the road end, it may take too much gravel where this isn't feasable.

If the gravel is completely saturated in the morning & is soft, there's no way I would recommend pouring. Weather is completely uncontrolable, & there is no reason to risk the lifespan of a 50+ year driveway over a 2-3 day delay.

One more thing: If the gravel is completly saturated, the concrete will have far more tendancy ot "bleed" out of the top, which can greatly effect it's resistance to future failure. Not worth doing always, sometimes you just need ot concede to Mother Nature.

tpolk 04-30-2010 07:33 PM

my thought on a wet sub grade is not how it effects the concrete but for sagging in soft spots

qoncept 05-03-2010 08:26 AM

Well, we ended up with just maybe an inch of rain Friday afternoon. It was finished before I got home (I couldn't get it covered during lunch) and it was a bit wet at the end. I sucked out with a shop vac enough to make it just have a small puddle here and there. It was dry all day on Saturday and the pour went well. I'm a happy camper. Thanks for the input, everyone.


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