Reducing Sulfate Attack on Existing Concrete Foundations

[TDAA]

I am looking at several homes with sulfate attack on the grade beams, near the ground surface.

Background:
1. The homes are about 3 years old.
2. Water Soluble Sulfates range form 1.2 to 2.7%.
3. We specified Type V cement for the mix, although not sure what the structural specified or contractor used (looking into that).
4. The client says the grade beams were water proofed.
5. Drainage is away from the houses.
6. There are perimeter drains at the base of the grade beams leading to an underdrain. Inspected at construction.
7. There are drains on the interior of the crawlspace that lead to sumps (cycle frequently). These were added after the fact (about a year ago) due to seepage.
8. The is an 8”void below the grade beams. Inspected at construction.
9. Water seeps from a slope behind the houses (houses near toe of the slope) that leave white crystal deposits when they dry.


We are currently looking at intercepting the water on the slope, and are looking into placing a deeper drain behind the homes to cut off the water seeping to the crawlspaces.

What other methods (if any) can/should we be looking at to reduce the deteriorating of the concrete? The builder has applied a paint-type sealer to the concrete at the ground surface; however, that is doing nothing for the situation. Obviously the builder does not want to spend much, if possible, but wants to be sure the homes will last.

 

[mcutchi]

what you are doing is excellent, i.e. direct the problem away from the concrete. At a recent refinery project, we used an epoxy paint to "surface improve" the concrete (after smoothing out the surface) - this stuff is wonderful at isolating the concrete from the sulphate attack. Surface preparation is everything.

Paint-type sealers do decrease surface porosity, but are not hard-wearing enough for anything other than mild exposures.

Also, make sure problem is sulphates - Type V is bad against chlorides, even at low concentrations.

 

[unclesyd]

Here is company that makes several products for improving the corrosion resistance of concrete.
We use several of these products in our industrial waste treatment facility.

http://www.sauereisen.com/c_prod/c_resist.asp

 

[LCruiser]

The surface problem is secondary, and cosmetic. You need to ensure water stays away, completely, from the concrete. Drain the water away outside and below the footing. Check not only what the supplier says they supplied, but if things get ugly find out how much Type V the supplier purchased during the period in question. Sounds like they might not have followed your recommendation...