Concrete for grout

[SperlingPE]

Would you substitute concrete for grout?
The concrete would be a plant mixed f'c=3500 psi mix.
Largest aggregate size would be 1/2" diameter.
I think I need to check code requirements.

 

[jike]

The size of the largest aggregate would depend upon the space that it will go into. If this is being placed in masonry cores, check grout space requirements per ACI 350. 1/2" aggregate is probably too large. Make sure mix is flowable.

 

[SperlingPE]

This is going in cores for 8" cmu.
The contractor wants to use the footing concrete mix with extra water added at the site after pouring the footings.
I am going to deny the request.
1. the concrete mix has an air entraining admixture
2. no way to control the mix w/c ratio at the site.

 

[fepc]

If you have horizontal and vertical reinforcing in the walls you will have a good probability of getting voids if the grout has a coarse aggregate. I always use a fine grout in that situation. Also a super plasticizer will give the fluidity required, but it costs more money than water. It does give you higher strengths. If you are testing the grout use cubes as per ASTM C 1019 and not cylinders as you will not get an accurate reading of the strength. It will be low.

 

[PT999]

Can the small round cylinder molds be used instead of cubes
These are about 2 or 3" in diameter and about 4 inches long
(I don't know the size exactly)

If not, what are these intended for?

 

[SperlingPE]

Thanks for the info.
This was kind of a on the fly question.

 

[Ron]

Grout is just a form of concrete with smaller aggregate. Provided you can consolidate appropriately and the strength requirements are met, they are completely interchangeable. The aggregate size typically dictates what it is called. Grout is generally concrete with an maximum coarse aggregate size of 1/4" to 3/8" and a high slump.

Mortar, grout, and "concrete" are all concretes with different aggregate and slump ranges.

 

[SperlingPE]

I know that grout is a concrete product.
My decision to deny the request has to do with execution in the field. The contractor proposed to use leftover concrete in a truck for grout. The concrete was a 3000 psi mix with 1/2" aggregate and air entrainment admixture among other admixtures. The contractor proposed to add water to whatever unknown amount of concrete and then use as grout.

 

[fepc]

ASTM C 1019 requires the mold for the grout cubes to be made from the masonry units with which the grout will be in contact. These units will absorb some of the water in the grout which simulates the grout in the masonry wall. You will get higher strengths which are more accurate indications of the strength of the grout in the wall. Using cylinders will give you results which will be lower as the excess water will decrease the strength of the grout. Using the proper test may mean the difference between rejection and acceptance.