Masonry Cement vs. Mortar Cement

[Philip.screw]

A discussion came up about whether we should be prohibiting masonry cement in our specs. Specifically, we prohibit masonry cement (ASTM C-91/91M) but allow using mortar cement (ASTM C-1329/1329M). Are the differences between the two significant enough to prohibit masonry cement? Is there a case where masonry cement can be used interchangeably?

jike has a great thread discussing this here https://www.eng-tips.com/threads/masonry-cement.235479/

This post is close to 15 years old, and some of our engineers want to know if prohibiting masonry cement is still valid / common.

 

[bIockhead]

I don't think this is really a "thing" anymore, where you should be most worried about verifying that whatever ends up being submitted for approval actually meets the standard and is being used in an application that makes sense for that particular product.

Not really addressing your question, but in the range of masonry problems I've seen with mortar, there are SO many things that deserve any attention before this. I'm relatively young and as I understand it, this was a contentious issue back "in the day" that has largely gone away, hopefully for good reason. Put me on team "who cares" until someone convinces me otherwise

Apologies for the lack of helpfulness in my reply here!

 

[Celt83]

My understanding these days is the decision to not permit masonry cement is linked to how you designed the element.

Refer to TMS 402-16 Table 8.2.4.2, the allowable flexural tension of Masonry Cement mortar is significantly lower than Portland Cement/Mortar Cement. If you didn't consider the lower allowable stress in design then it should be prohibited from use.

Similarly Table 9.1.9.2 shows a significantly lower modulus of rupture when using Masonry Cement.