Identify Bond Beams in Exisiting cmu walls 2

[jim57]

Looking at a house in which a new foundation was installed to raise the house out of the flood zone. Trying to determine if bond beams were installed. is there a difference that can be seen in a completed cmu wall. Also the wall is 35' long and 8'8" above grade. Shouldn't there be a pilaster to break up the unbraced length?
Thanks

 

[JAE]

If it is reinforced with vertical bars and grouted cells every 2 to 4 feet on center then pilasters wouldn't do much or be needed.

Typically we have a contractor drill small holes to determine the extent of grouting in the wall (then patch the holes).



Check out Eng-Tips Forum's Policies here:
faq731-376

 

[jim57]

Would the drilling work for the bond beam? That may be cumbersome.

 

[jike]

Sometimes you can wet the wall and the shadow of the grouted cells may be seen. Whether this actually works will depend upon the actual temperatures and humidity.

There is also an x-ray method where all the grouted cells will show up but I suspect this may be cost prohibitive for a residential project.

 

[TehMightyEngineer]

If you get a large thermal differential between the inside and outside faces of the wall it might show up on a thermal imaging camera, those are fairly cheap to rent.

Professional and Structural Engineer (ME, NH)
American Concrete Industries

http://www.americanconcrete.com

 

[Ingenuity]

GPR will non-destructively determine which cells are grouted and location of any rebar. Take less than probably 1 hour. Access to only one face is required.

 

[hawkaz]

Since this is in a flood zone- the wall may be solid grouted. If so, locating grout may not help you determine where reinforcing may be. I agree with using GPR

 

[emmgjld]

A simple Pachometer will do the job. Actually just performed that testing for a contractor last month, looking for bond beams and grouted columns.

 

[msquared48]

If a cell is grouted, lightly tapping the surface of the cell with a small hammer will give a lower pitch than one that is not grouted. I have used this technique many times. Sometimes, you can "read" the bond beams from the exterior too.

A rebar locator may help, but they have depth limitations too, some only 2" to 3" which may not be good enough for an 8" wide wall.

Mike McCann, PE, SE (WA)

 

[Ron]

GPR will do both bond beam and filled cells. Another way is to go into the attic and see how the trusses are anchored and you can likely see if a bond beam was placed using lintel block.

 

[concretemasonry]

Just looking at a "finished" wall will give little information since quality CMUs will have the same appearance irregardless if it is a bond beam or lintel unit. msq has right idea. A small hammer with a good tight fitting handle is very valuable (if you are not tone deaf like my wife). You can even determine whether a CMU is filled or hollow and even how may cores (2 or 3) it has. - Working as an engineer for a CMU producer, it became a very valuable tool on problematic projects. - You could even find voids in grouting of existing construction if the wrong units were used for the bonding specified.

Sometimes it makes you want to wear a cape and carry a large magnifying glass for additional credibility.

Dick

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

 

[darthsoilsguy2]

they sell/rent equipment to scan for ferrous metal and orientation, IR cameras for thermal differences through a material, GPR for density variations in a material, then slightly destructive measures. although there are some reasons to object to it... a nuke gauge on the wall in backscatter should also tell the difference between grouted/ungrouted cells.
i've messed around with all but an interesting option is non-industry specfic is that metal detectors also work. i have a vintage "treasure finder" that came from Radio Shack in the early 80's that runs on a 9V battery that is a good first pass and is worth buying just to pick up roofing nails around the yard. The detectors that surveyors and town plumbers use are significantly better at finding metal.

 

[jim57]

Thanks to all. Great information