Masonry Subject to High Sulfates

[Deker]

Does TMS 402/602 (or any other masonry standard) offer any guidance for specifying material properties to protect foundation walls exposed to soil with high sulfate content?

 

[BAretired]

For concrete, there is a sulfate resisting cement. It used to be called Type 5, but I believe that changed to Type 50.

For brick, I don't know if there are any measures to be taken, other than using sulfate resisting cement in the mortar.

 

[Deker]

Thanks, BA. Since the masonry standards are silent on the issue, I called a major local block supplier to get their input. The rep I spoke to said that there are some local cities that require blocks be produced with Type V cement for municipal projects, but outside of that he has never seen or heard of any special requirements. Swapping out the cement requires a special order with a minimum 15,000 block quantity, and the plant has to be willing to shut down to clean out all the standard Type 1L cement to swap it out with Type V. Anecdotally, he also said that he has seen the entire first course of a freestanding site wall completely eaten through from soil sulfate, leaving the wall entirely supported by the vertical reinforcement.

 

[BAretired]

In that case, it may be best to substitute concrete walls with Type V cement for masonry walls in contact with sulfate contaminated soil.

 

[JLNJ]

You might be able to use 1L cement and have the plant add an additive to their mix. We have done this for permeability, but not for sulfate resistance. You might contact the people who make Xypex and other similar additives and ask them.

 

[Deker]

Thanks, JLNJ. I did briefly look into adding silica fume to increase sulfate resistance, but ultimately the contractor decided he would rather waterproof both sides of the wall and use standard block.

 

[masonrygeek]

Sulfate attack is rarely a problem with masonry, especially on the clay brick side. Most of the deterioration occurs in the mortar and if it does happen in the brick it takes decades for issues of salt crystallization to cause problems. Concrete masonry could be more susceptible, but I rarely see any problems with sulfate attack. If you want to use a masonry cement mortar instead of a portland cement lime mortar that would increase the sulfate resistance (

https://www.cemexusa.com/products-a...ations/type-n-s-m-masonry-cement-and-mortar).

Of course, I have to ask why you don't just use a waterproof coating on the below grade masonry to help protect it? The reason TMS 402 and some of the ASTM masonry standards don't address this is because it rarely is a problem.