Concrete Waterproof additive

[GSUK]

Hi,

I need to lay foundations for a shed. Problem is the garden is only 1ft above the natural water line so as I dig the trench its half filling with water.

Is there some kind of additive I can add to the concrete mix to ensure it sets in such wet conditions? Also, any advice on best mix of aggregate/sand/cement would be appreciated

Thanks,
Glenn

 

[PrenticeBoyofDerry]

Concrete can cure underwater, but I'd wait for a dry day as additional water that you have no control over, will compromise your mix.

 

[garyo]

How quickly would the trench refill if you were to pump it dry just before pouring the concrete?

 

[GSUK]

I would need several weeks of dry weather for the river down the road to drop before I'd see my garden dry up.

I reckon the trench would fill up again within 10-20 minutes easily.

Is there not an additive you can add to the mix that helps concrete cure in very wet conditions?

 

[PrenticeBoyofDerry]

Is there not an additive you can add to the mix that helps concrete cure in very wet conditions?

The structures that are built in water, like bridges, oil rigs, wind turbines etc..
Use a method called caission, don't think it will help you though!

The problems is that your concrete will be saturated by the excessive water, which will be an unknown quantity, so you could never get your mix design right, unless you can divert the water flow to another area, then do the pour, your stuck.

 

[Static]

Dewatering is best way as others have said.. digging a larger deeper hole near the one you wish to pour in and it should lower the local water..

 

[ajrobb]

digging a larger deeper hole near the one you wish to pour in

Would he need a sump pump with that?

 

[Static]

digging a larger deeper hole near the one you wish to pour in

Would he need a sump pump with that?

Only if it doesnt drain his smaller dig sufficiently.. holes are cheaper than hiring a pump for a few days

 

[Adrian80]

Dig the hole for the foundation, line it with dpm. dig a run out channel to another hole for the excess water, mix a bit of accelerator in to, stand near the other hole with a bucket ready to bucket out the water when your run off hole gets a bit full.

 

[GSUK]

Sounds like you've done this before Adrian

Thanks for all the tips guys. I'll probably dig all the trenches this weekend in prep for the pour over the following long weekend. I'll let you know how I get on.

Cheers

 

[noseall]

Reminds me of a time when we were filling large holes (2m x 2m x 2m) with concrete that were 1/2 full with water.

We managed to pump them all out just before the concrete pump reached each one.

Except the last hole.

I said just fill it and let that bit of excess water flow out.

And did It flow out!

All 90 gallons or so of cement coloured water all over a posh manor house parking area. It took hours to clean it up.