Masonry grout - lack of consolidation - repair

[ATSE]

The structure in question is a new reinforced masonry equipment building, 20ft x 40ft, single tall story, with (2) 12ft tall x 12ft wide roll-up doors side by side, near complete. Steel roof and equipment already installed. High seismic area, with out-of-plane demand governing the design.

The contractor did not use lintel blocks, which actually worked out better for post-inspection, since the lack of consolidation is clearly revealed.

See the attached photo, looking up at the lintel.

Instead of 9" slump grout with 3/8" gravel and w/c = 0.67, it appears more like 1" aggregate concrete with 2" slump. The exposed bars show no real bond.

My concern is the lack of integrity for the entire structure, especially at the side with two large openings, which is more like a portal frame.

Any suggestions on evaluation / non-destructive testing / repair? I will be having a conversation with the owner soon, telling him that the structure is not acceptable as constructed, and advising to withhold payment in order to pay for future retrofit work. I'm sure he's going to ask, "Well, what do we do now?"

Complete demo is not an option. Reinforcing on the interior with flat steel plate and thru bolts is one option. Crack injection like Sikadur 52 in every cell may be possible, but seems unconventional and a ridiculous amount of work.

 

[Ron]

DO NOT LET THE CONTRACTOR GET AWAY WITH THIS!!! The next job he will try even more. Kick his a$$ on this an get it replaced. He has violated many conditions that I will assume the design covered. If you let him get away with this, you will assume the liability for his screw-ups...not good.

 

[haynewp]

Besides the lack of consolidation there can be problems with low slump concrete bonding to cmu units. I don't know how to justify what strength can be developed for the rest of the building walls also.

FRP or steel plating can account for tension on the internal face, and take in-plane shear, but I think you have to discount the rebar acting in tension for the walls bending outward. I don't see how the Sikadur can replace the consistent bond that was intended between the grout and the units.

I would consider building a new internal wall adjacent to the existing out of reinf. concrete with the existing wall prepared to bond to the new concrete, but the concrete would be adding more seismic mass. If it was 8" block, 6" RC walls might can be made to work and design them as taking the entire load.

 

[concretemasonry]

The grout obviously does meet the specification., which if the contractors responsibility and he just tried to get a way with using a convenient concrete that was available. Because of this all strengths of any of the structural elements must be assumed to be inadequate. Excess or stronger grout is not a solution since the purpose of the grout is to bond the steel to the masonry elements. Therefore, the shear and flexural strengths and stiffnesses are not adequate.

If you allow a fix, you will be responsible for any results in failures of and other elements that accumulate different loads.

Hopefully a detailed examination will revels where there are accumulated conservative assumptions. there are always excess capacities that can accumulate enough of a "cushion". Don't fall for a strength test of the improper grout since even 10,000 psi grout will not be enough even if the construction was not right and the site inspections was inadequate.

Dick



Engineer and international traveler interested in construction techniques, problems and proper design.

 

[ATSE]

Thanks for the replies.
If you were hired to evaluate and repair (and tear down was not an option), what would your plan of action be?

 

[SteelPE]

I have never really faced such an instance. I would probably just walk away from the project. Engineering a fix is going to be difficult and time consuming. You will probably will not be compensated for your efforts either.

That being said. When face with rehab projects of URM, I usually propose three repair methods.

1)Installing new reinforcing to meet both horizontal and vertical steel requirements (horizontal reinforcing can be helped by adding an additional bond beam at the top of the masonry).
2)Adding a new wall inside of the existing to take the code required loads (I usually propose a metal stud wall).
3)Demolition of the problem areas.

When all is said and done, we usually end up with method 3.

I imagine installing new steel lintels would be required in this instance.

 

[ron9876]

At a minimum I would require that all grouted cells be sounded full height with a hammer to see if they all have grout full height.

What do the results of the grout tests show? Was the material actually grout?

If it appears that the grouted cells have grout full height then I would require that the face shell be removed to allow visual inspection. If there is a problem with the grout placement then adding new reinforced grouted cells would likely be the best solution.

 

[cvg]

first of all, tear down is always an option. who says it isn't? And it might be a good tactic to hammer the contractor with the tear down option to get him to agree to an expensive retrofit. but you are going to need a lot more than just a few photos to convince the folks holding the purse strings. the forensic investigation might be quite expensive to prove anything. partial or total tear down might be faster and more economical.

http://www.eng-tips.com/viewthread.cfm?qid=286468

 

[haynewp]

An internal framework of HSS tubes face bolted to the CMU at determined grout filled locations may be another option. The tube work may be placed at a vertical and horizontal spacing where minimum cmu strength can be assumed. Bracing can be provided within the tube work, but you will still have seismic criteria to meet for the system.

The whole thing is a poor situation. I know you want to avoid destructive testing but some sort of testing that can show a grout placement consistency you feel comfortable with accepting (with some level of adequacy) through the rest of the building walls may be warranted before a solution is decided on.