masonry block fill: grout vs concrete 1

[boffintech]

The structure is masonry stem wall: footing with two courses of block placed so that top of course #2 is top of slab-on-grade and block is used as form for the SOG. Job specs call for these bottom two courses of block to be filled with "3000psi 3/8" pea gravel mix".

The contractor failed to request a masonry inspection until AFTER all the stem walls and SOG were placed. Upon arrival to the site the inspector found all the stem walls poured solid with concrete, apparently the same concrete that went in to the SOG. The contractor almost claimed that the pea gravel mix was used but realized they didn't have an approved mix ID or any delivery tickets for any pea gravel mix.

The inspector dutifully notified the EOR of this discrepancy and was told not to worry about it because those two courses of block were below grade but that the rest of the block had to have the correct pea gravel mix.

Clearly the SOG concrete mix will not meet the requirements of ASTM C476 and clearly NONE of that masonry work was inspected according to the schedule of special inspections either before or during construction.

Why is OK to use the SOG mix as block fill below grade and what happened to the requirements for inspection?

 

[hokie66]

The reason that the EOR had no problems with it is that there were only two courses. The pea gravel mix is to facilitate complete filling of block cavities, but almost any concrete can be used to fill two courses.

 

[concretemasonry]

The EOR exercised judgement by accepting the liability of the SOG mix in place.

He probably realized that he really did not need (or want) the 3000 psi, since 2000 psi may have been better and more acceptable (typical boilerplate error).

Since there probably was not a substantial amount of steel in the grouted portion of the 2 courses of the block wall, any requirement for a fine grout would be unnecessary and possibly detrimental. Stronger is not always better.

If you look closely at the ASTM aggregate gradation requirements for the grout aggregate, it contains a footnote (common to many aggregate specification like mortar and grout) stating that gradation "variations" can be permitted if satisfactory historical performance can be demonstrated. This is obviously a sort of loop-hole, but can be justified by particle shape in some cases.

If there was a sample of the SOG mix, this could be used to inform all parties that the SOG mix did not meet the requirements for coarse grout. This would also be an aid in getting closer attention to the materials required and need to schedule those materials and inspections in advance.

Often, unnecessary inspections and sampling for minor events tend to water down the importance of the areas that really require inspection. This is why good masonry designers try to avoid unnecessary reliance on hidden parts of a wall that require inspections and an unnecessary interuption in the natural flow of construction. - If the wall is adequate (right units, plumb and good mortar) without something hidden, why create situations that can create more problems. I have seen projects of 10 or more 15 to 20 story buildings of 6" loadbearing masonry built simultaneously without any inspection clean-outs for grout because of a good inspection program and advance planning. - No site prisms and only routine grout samples. All masonry units(4 different strengths) sampled prior to delivery and rigorous grout core inspections where grouting was necessary.

Since there was grout required, was there an approved grout mix? This type of situation can be avoided by proper submittals and agreement where variations from the prescribed process could be permitted in writing. Little glitches early can be used to smooth out the rest of the project and future projects.

 

[boffintech]

There was no approved 3/8" 3000 psi concrete mix. I think a few people back at various offices are kicking themselves for not picking that up.

Also, the SOG mix had a 5" slump. Those dry block probably sucked the mix dry. So lots of shrinkage, lots of way over sized aggregate. Plus I found numerous bed joints 2 to 2.5" thick, and discovered just by asking the mason that the cross webs were not mortared.

I say breakout the chipping hammers but I'm just the inspector.

 

[hokie66]

The EOR has ruled. Leave it alone.

 

[henri2]

boffintech,

It really comes down to the manner the building dept implements special inspection provisions of the building code. In some jurisdictions, the EOR will have the final say....while in others the BO's decision will be final.

 

[msucog]

i'd be less concerned about the actual block fill and more focused on the rebar (whether epoxied, in place, loosely set in to the cavity, etc). i've had situations where we simply went back and cored the foundation block fill to test the compressive strength since the dowels were checked during the footing construction--before someone "learns me up" on why that's not the same as grout, i'm already aware and agree, it's not the same. and yes, the grout spaces were not checked so the EOR is the one that has to make the call. the EOR has never been concerned (on my jobs) about the couple of block high in the foundation since they're fully grouted.
in the past year or so, i've tried to make myself more a presence on the project by spear heading such issues before the work starts. the architect, engineer, and/or owner should always invite the testing firm to the preconstruction meetings but it doesn't usually happen that way. a little effort on my part on the front end can typically remove additional headaches for everyone down the road. especially since i'm the one that has to say that we performed the special inspections.
i've got a question about special inspections elsewhere but i'll ask it on another thread.

 

[spats]

I think boffintech said it all in his follow up remarks. No reasonable engineer would accept 2 1/2" thick joints, and cross-webs not grouted at filled cells. C476 grout is specified to be 8"-10" slump for good reason. 3000 psi pea gravel concrete should never be specified for masonry grout.

 

[msucog]

spats, i have personally called the EOR while i'm standing there looking at a contractor placing concrete (after i recommended 4 times that he immediately stop the pour) that's 4 hours old and coming down the chute in clumps bigger than basketballs for footings in a sizable warehouse. they'd only added about 40 gallons of water and it was still that bad. on top of that, their vibrator stopped working 2 hours before that. the EOR let it go and the building is complete (probably being moved in to as i write this post).
i wish all engineers i run across were like those on this board. heck, i'll be happy to just see them make the contractor consolidate the grout by mechanical means or make the contractor tear out walls for 3 hour grout going in them.
in case any of you folks think today's construction quality is somewhat okay or maybe good...i completely disagree...it's horrible...don't be fooled. i wish there was a "contractor safety factor"...it'd be a big number...but that's just my opinion.
unfortunately, there almost needs to be a lot of stuff to start falling, killing folks, and lawsuits flying before things will change. if we see a sizable earthquake around the new madrid or charleston, i expect we will see some horrible things on tv...again, just my opinion from here in ga. i hope i'm wrong...