# Rebar Positioners vs Tiewire



## heavyc (Jul 2, 2013)

Never have figured out why vertically reinforced cells with rebar would require rebar positioners instead of tieing a physical connection with tie wire.
All the positioners do in my opinion is choke the cell down. 12" block not so bad, but most of our load bearing work is 8". Once we install horizontal bars then positioners with vertical bars there's not much room for successful grout placement. Fine grout different animal all together that flows nicely. The job we are on has a grout mix site specific, QC designed along with engineers approval for pea gravel mix grout. PITA
Fine grout/ tie the bars call it done and done well. Just wondering what all the excpert/ skeptics view are?
Yes we've put in RFI'S and submital requests for fine grout. Turned down and specifically directed to use the mentioned grout. :blink:


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## griz (Nov 26, 2009)

In your RFI did you state the problem of the spec'd grout not being able to flow properly?

In issues like this I always liked to state what specific problem the spec may generate and if installed per spec. may result in a design failure which would be the engineers/Architects problem.

That way my concerns were out on front street for all to see.

Many times the spec was changed.


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## Tscarborough (Feb 25, 2006)

See if they will allow a self consolidating mix with the specified aggregate. It is good for situations like this.


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## heavyc (Jul 2, 2013)

During preparatory the guide lines clearly stated. Written and verbally that no changes as far as vendor/ materials submitted and approved shall be changed, unless said vendor/ material was no longer produced or through an act of God could not be obtained. That's the long and short of the situation. We are pushing the envelope on slump to 11 ++ to achieve a better fill. We also switched out our pump with our Grout Hog and things are looking much better.


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## Fouthgeneration (Jan 7, 2014)

Are you using Concrete sand (ASTM144) instead of masonry sand?
can you add some fly ash and or air entrainment?

I personally believe that slightly off center rebars are less of an issue than voids created by locators and mortar droppings, and the fact that "rubbing bars" actually need a longer lap than bars with a little grout between them.:whistling

Your pea rock may be just bias toward the large end(mostly 1/4"+) for use as a tile filter material, adding aggregate sized between the sand max and the Pea rock minimums might improve pumpability.

Are you using mixed block that consist of both stretchers and corner block? Or is the half bond getting a little strange between CJs?

You could buy CMUs without the center web "handle", which would ease the flow issues at the cost of some production.

Edit: First page of Google search, Too much P leads to aggregate separation....

When filling a "tower" silo the first time the mix separates enough to go out of "spec" Have the operator fill the grout mix tower as often as possible to decrease the free fall of the mix. If you are even using a silo...


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## heavyc (Jul 2, 2013)

We are thinking the super "P" over kill in the mix design is our culprit. I'm thinking if I heard the QC correctly say that they were adding 30oz. WTH? Generally the amount when required is 1oz. per yard.
Our PM has a strong background in concrete and the alarm bells went off along with many many emails. Since this discovery the mix has been flowing well. 
Our fins are less than 1/2" as reported by the special inspector in his report. Bar placement stated above average. 
Seems like everything is coming together nicely now. We are thinking about pumping again.
Not a concrete/ grout mix specialist. Just placed large amounts over the years. Don't hold me to the ratios as I'm hearing parts and pieces of information. The issues are between our PM and the GC's QC and the batch plant. Greatfuly so.


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## concretemasonry (Dec 1, 2006)

For concrete masonry construction, there are many different units that can be used. One of the most common is a unit that has 2 webs at 8" on center and open ends. The cells align perfectly. That sounds like either a very tall wall or poor job of design/engineering.

I was on a few projects(5) of 5 to 10 buildings in Brazil that were built under the ACI 530 requirements. They used truck delivered grout (8-10" slump) using the appropriate ASTM specifications for aggregate in the grout. The mortar was the same for all floors because the mortar does not control the strength of the 2 block high prism (the block do). The apartment buildings in the 5 projects were 7 to 20 stories tall that used partially 6" reinforced and grouted masonry construction. The amount vertical steel decreased as you go up in the drawings that broke the building in section of 3 floors to make the costs lower. The block were not required to have clean-outs and representative grout cells were inspected with a TV camera. If they failed, clean-outs had to be cut in the wall before it was grouted and later walls in that building had to have clean-outs. The block were inspected at the plant well before delivery and color coated by a paint spray in one of every 4 block, so there was not the typical testing and sampling problems. They used 3 or 4 different strengths of block for each building depending on the number of floors. They also made special corner units since many buildings had 45 degree or 30 degree wall intersections. One thing the producer did was to turn all block over from the typical manufacturing process, so there was a wider face shell and webs on the top of the delivery pallet to make handling on site easier and minimize the waste and slop that can fall down into the grout cavity.

They did a floor per week for walls and floors. Since they were apartment buildings with interior bearing wall also, the reinforcement was not that heavy.

It is amazing what can be done if the GC is also the owner and the did his own masonry construction, and the registered engineers were smart and followed the U.S. standards outlined in ACI 530, which is the "bible" for block and brick masonry engineering and construction in the U.S. and in most of the Americas (south and north).

The engineers did look at some of units made in California to get ideas to keep the cost down.

Many block producers can make specialty units if they see there is potential volumes. When I was with a block manufacturer, we made a special 6" block that was an odd length since the walls had 45 degree corners that had to be laid in running bond that were exposed in a college building.


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