sand - mortar vs. grout 1

[boffintech]

The # 2 sand for fine grout in table 1 ASTM 404 appears to be identical to the sand in ASTM C144 for mortar.

Am I correct in interpreting the following:

1) if the engineer has specified #2 sand as aggregate for fine grout then the same sand can used to make mortar and grout on a job.

2) if the engineer has specified # 1 sand as aggregate for fine grout than the mason will need two separate sands: # 1 for grout and # 2 for mortar.

 

[concretemasonry]

You are right, but one sand may be used for both.

In reality, the gradations are not "cast in stone". If you look, you should find a common note that permits variations from the standards if it can be shown the materials can be shown to have had a good history of performance.

There are a few reasons for the permitted variations:

1. Particle shape has a large effect on the workability of mortar. Workability is the most important property of mortar and in most cases much more important than the strength (see ASTM C470 Appendix). Even for engineered masonry requiring prism tests, the mortar has little effect of the prism test results(f'm). - If CMUs, the units strengths are really the governing factor.

2. The amount of aggregate permitted in a mix has large variations in the amount of aggregate, especially with a proportion specification (2 1/4 to 3 times the volume of the cemtiteous materials).

3. In both, mortar and grout strength is not really the critical item. For mortar, it is workability. For grout, it is the ability to fill all voids. In many applications, high strength grout (greater than the f'm of the hollow masonry prism) is not recommended.

You can find this note is quite a few of the specifications because of similar situations.

If one material is requested it is up to the engineer if the submitted materials have a "good track record".

 

[boffintech]

When you say that 1 (one) sand may be used for both (mixing both mortar and grout), you mean that # 2 sand meeting the requirements of ASTM C404 can be used for both, correct?

# 1 sand meeting the requirements of ASTM C404 can not be used for mixing mortar, correct?

I guess what I'm asking is can a sand simitaneously be #1 and # 2?

 

[concretemasonry]

It is obvious that one material can meet both the specifications since there is a such a wild range of premissible amounts passing the various seive sizes and C144 permits variations in section 4.4 based on performance.

The C144 specification is required for mortar. The same material meets the requirements for #2 sand for C404. The sand #1 is just a way of permitting a wider range (coarser)sand to be used since the gradation for grout is not critical.

If a specifier wants to make things complicated, be can specify two different specifications (one for grout and one for mortar) That seems to be a complicated way of specify ing the gradation for a material that has very wide permissable ranges.

To be blunt, the specifier better have a good reason (unusual application or material availability for pre-proportioned materials) for specifying only sand #1 for the grout, since tight sand gradations are really not critical for grout and one specification should work everywhere. - I suppose it may be a boiler plate spec that has not been enforced or noticed for many years and no one ever asked the question.

If I was specifying a gradation for grout, I would just specify C404 with no detail for the sand type. I would specify C144 for the mortar. If the grout was site mixed, I probably would get the same sand either way, which is not a problem. If pre-proportioned (Spec Mix)mortar and grout, I would get what the local industry has found to work best. If the grout was plant mixed, I would probably get concrete sand in the grout, which would also work.