Masonry Special Inspections - Low Mortar Breaks

[cpdonahue]

I have a small project masonry project for which 1 set of 3 mortar cubes were made and tested for compressive strength. Low 28-day strengths were 600 psi for Type S. There is only 1 set due to size of project and contractor not calling for testing. Can the prism method by done (ASTM C 1314) by cutting out some prisms (non-grouted masonry) from the existing walls and testing for Prism Test?

Are there other options to verify in-place mortar strength? I know generally speaking, mortar cubes are to act more as an indicator of the trend of the strengths, and not actual in-place strength.

 

[JedClampett]

I'm not sure that strength testing is even required by code. First I would do some sleuthing about the mortar mix. Did they use bagged mortar mix? Was it mixed correctly? Or was it batched? Were the proportions correct? It sounds like you got a bad batch and no amount of testing is going to prove its adequacy.

 

[masonrygeek]

I wouldn't worry about one low mortar test result since mortar testing is fraught with all sorts of issues and as you say, doesn't really provide a good indicator of wall strength. Take a look at NCMA TEK 18-01 (

https://ncma.org/resource/evaluating-the-compressive-strength-of-concrete-masonry-2015-ibc/).

It provides some methods of doing prism tests even for in-situ masonry. There are other NDE methods such as impulse-echo, but that may be too sophisticated for this project.