DIY watertight concrete slab

[tomfe]

Is there a concrete additive for slabs which does away with a dpm?

I know if I get ready mix I can get structural waterproof concrete but all the liquid stuff I've got says not suitable for structural concrete.

 

[ree]

Your post is confusing: there are masses of so called "water proofing" additives for mixing into a pour. Just google them.
There is no substitute for pouring on to a membrane (a DPM) if thats what you mean by "waterproofing"?

 

[tomfe]

There are a number of water proofing additives but none that I have found available to me are suitable for a direct replacement of a dpm.
For example:
http://www.bostik.co.uk/diy/product/none/Integral-Waterproofer/207

There are commercial products which are available in bulk e.g.
http://www.sikawaterproofing.co.uk/products-systems/sika-watertight-concrete/
The way the site is I would prefer to waterproof the raft.

 

[theprinceofdarkness]

SBR it says it is good for 30m if you are building a dam. You can paint it on as a tanking paint. Its nicer to use then the bitumen based products. It makes the cement go off like tough leather, i.e. its a bit flexible.
Frank