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Block grout requirements.

4305 Views 7 Replies 4 Participants Last post by  JBM
Ok, materials are delayed so I have some time now.

I am not now or have I ever advocated type S over grout for ANY reason other than convenience. The ONLY bone I was picking was the comment that grout must be used...NOT MORTAR. While I absolutely agree that mortar in the form used to lay brick or block would not be acceptable, the exact same "souped up" type S is acceptable since it

a: completely fills the voids
b: has aggregate small enough not to impede the flow (3/8 or less)
c: ends up @ 2000psi (or darned near close, often over and if you're scared just add some more cement)

Those are the 3 specs that I have seen for grout. I know that grout doesn't need lime...that was never a reason that I gave. And YES mortar is much more expensive than grout, but if you already have too much block sand (I can get 10 yds of sand for the same price as 1 or 5 or 9 because of minimums) and if you are doing a job that will just take a few days and don't want to bring in and then take home a secondary mixer, type S mixed to a consistency of a thin milkshake will do what you need it to. Convenience

It probably won't surpass the specs by a mile but it should meet them. The grout is there for 2 add strength and to "join" the rebar and the block or to allow them to work together and give the wall some tensile strength. Mortar as grout does both of these satisfactorily.

JBM brought up a good point. Mortar when it gets beyond a certain thickness (2" is a common number thrown out)it gets weak and can break but since the cores of the block are holding the mortar/grout together this isn't really a concern. There isn't a load applied directly to the grout, the grout is transferring load

Should type S rather than grout be used in highrise or earthquake or tornado, unless it's been engineered that way which is unlikely, but in normal residential and light commercial situations (single story loadbearing, partitions, infill between steel posts, firewall etc...) it will perform adequately.

As an aside. concretemasonry brought up wet soil. I redid a wall of a basement. 8" block, 8' high ZERO steel anywhere and backfilled with heavy clay soil 7' high. Also the cottage was actually built in a filled in sluiceway from an old mill, so it was in a depression and also very close to the water. It took 40 years for that grossly underbuilt wall to fail. I'm pretty sure that a 12" block wall with the cores filled with 5/8 or 3/4 bar and grouted with type S every 4' would have given that wall another 40 years or more, well within the accptable lifespan of residential construction. In fact I haven't seen a block foundation built before 1980 that had any steel or was thicker than 10" block...most are 8" Most are in acceptable condition for their age

let the barrage begin
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Not much there about grout ingredients but at least this confirms last years argument that there is a 0.002 steel requirement and that joint reinforcement (I call it blok lok, you americans seem to call it durawall) can be used to make up the horizontal steel needed
The chart showing block size and fill heights is good to keep in mind.
I'm really just expounding on my argument in the foundation with frozen joints thread. I didn't want to clutter it up. The OP hasn't been back in some time

Also my code book is very different. for foundation walls, laterally supported a 12" block wall can only be 7' 3", 10"- 5'11, 8"-3' 11" and 6"- 2'-7", there is no differentiation between reinforced and nonreinforced, perhaps there is no zone 1 in Ont. I know we are in a zone 4 here, 0.002 steel requirement in all block walls.

they do differentiate non laterally supported walls and they are
6"- 2'
For your soupped up mortar to bleed enough water to ever test above 1500PSI I would think wouldn't happen consistantly, between the finer sand and the lime in the mix, the parts of core fill away from the block webs would set with excess water,= weak. lime makes the mortar mix less permeable and slower to release the excess water. Neat grouts are more "fool" proof....

On small jobs I'll use bagged concrete mix instead of core fill...sometimes I use 5000psi mix for antsy generals backfilling...(local bagged concrete < 1/2" 12mm aggerate)
3/4" "legal" on 8"CMUs and wider.

Maybe your Sand jobber could send out a pup trailer with the concrete sand & pearock behind the mason sand load?

I mix with mason sand & cement or PCL & mason sand to underbid the users of little and big bag mixes, Dried sand for most larger jobs is $illy.
ASTM graded concrete sand and pearock & portland + 1-2% hydrated 'S' lime for transportabililty.
I'd think on larger basements, the lower cost of grout would favor its use and widen your margins.

Type 'S' masonry cement without any lime? I'd check your MSDS sheets to confirm that, Limestone dust is common in type N as a plastisizer / partial replacement for hydrated "S"Lime.
Ok, first off my type S typically contains 0 lime...only plasticizer. They do act similarly though and a plasticizer will hold water. make a mix @ 2.75:1 and I am reasonably sure it comes up to strength. Remember 1800 PSI is an average for type S mixed @ 3:1. Average, there are many factors besides water that can contribute to low comp strength, including not enough water and excess heat. Also the grout bleeds lots of water, and within an hour often less the blocks are visibly wet wherever the grout has travelled, and usually within a couple hours is as stiff as block mud that is an hour old.

I wouldn't be able to get away with concrete. Too large an aggregate. As I said before, the specs I've seen have only been for max aggregate size
Im happy if your happy.
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