Using ASTM C94 Ready Mix Concrete instead of ASTM C476 Grout for Masonry

[Philip.screw]

I'm reviewing a masonry grout mix submittal, and noticed the submittal called the CMU fill out as ASTM C94 ready-mixed concrete. Our specs explicitly state ready-mixed grout shall be ASTM C476 grout for masonry.

I want to reject the submittal because it clearly does not meet the ASTM we provide in the specs but was wondering if ASTM C94 is an acceptable substitute for ASTM C476. Recently my boss has started to review our specs as they are pretty old and wants to know if there are new standards / acceptable substitutes that should be added / updated. My understanding is grout and concrete are similar materials, however, is there enough differences between the two that do not make them acceptable substitutes?

 

[Gr8blu]

See following links. As an example: one of your concerns might be allowable slump, depending on the application.

Grout for Concrete Masonry

INTRODUCTION Masonry grout is a cementitious mixture used to fill cores or cavities in masonry construction. While usually added for...

www.masonryandhardscapes.org

https://www.concreteconstruction.net/how-to/concrete-production-precast/understanding-astm-c-94_o

https://www.atlantictesting.com/wp-content/uploads/2021/09/Quality-Bulletin-Review-of-Technical-Changes-to-ASTM-C94.pdf

 

[waross]

Anecdote:
The difference between grout and portland cement.
A ceramic tile floor was laid on a fresh concrete floor.
Rather than grout, portland cement was used to adhere the ceramic tiles and also used as grout between the tiles.
The edges of the tile floor were restrained by concrete walls.
As the concrete floor cured, it shrank slightly.
The portland cement grout between the tiles did not compact as proper grout would have.
As the floor concrete cured and shrank, the compressive pressure edgewise on the tiles increased.
A few months after installation there was a loud noise one night.
In a line across the room, two rows of tiles had popped up to remove the force.
Beware the difference in characteristics between concrete and grout.

 

[dik]

In a line across the room, two rows of tiles had popped up to remove the force.

Neat anecdote...

 

[dik]

Ask them to provide what was spec'd... 50 years back there was no distinction. For concrete filled masonry walls, we used normal PCC, but with 3/8" aggregate and 8" slump. Worked well and as the water was 'sucked' out of the mix by the CMU, you could see the line of the grout fill on the wall. It left a damp line.