VOBB vs. regular 8" x 8" x 16" CMU
(regular CMU with no rebar)
This report by independent engineers show the dramatic quality difference in strength of using the VOBB method vs. using regular 8" x 8" x 16" with a comparatively weak mortar joint.
After reviewing the report results, the question has to be asked and answered "Why would anyone not build using VOBB considering the value/strength of the finished building/project?"
The following engineering tests have been performed by an international independent testing company. This company is Stork Southwestern Laboratories in Houston, TX. Their phone number is 713-696-6226. Their web page address is: http://www.storksmt.com/ Stork SWL is fully accredited with a rating of A2LA, by the Texas Engineering Societies, in Louisiana, by the LPELSB, etc.
link to the engineer report:
http://www.vobb.com/engineer-vobb-vs-reg-cmu/stork-vobb-vs-reg-cmu.pdf
"Results: As expected, the (regular 8" x 8" x 16" regular CMU) three tier stacks with only a mortar seal around the block perimeter exhibited the poorest bonding strength. The load values, based on a square inch area of surface for those VOBB stacks having two or three cavities filed were very similar in strength, meaning a third cavity does not offer a significant rise on lateral strength as opposed to a two cavity filled system.
It is also of note that the industry standard of a 60 psf force equals a lateral wind load of 150 MPH. The mortar filled blocks tested produced shear loads averaging 11,000 - 20,000 lbs, which will far exceed the 150 MPH industry rating."
Note various curing times:
3/8" rebar with grout in VOBB cured approximately two months
1/2" rebar with grout in VOBB cured approximately three weeks
5/8" rebar with grout in VOBB cured approximately two months
regular 8" x 8" x 16" CMU with no rebar approximately two weeks
Pictures showing the detailed testing process using 3/8", 1/2" and 5/8" rebar. There were three samples of each type of different test to get an average. There was one set with two cavities filled and one set for each size of rebar with all three cavities filled with grout. The test of all VOBB samples consisted of the following:
One 18" VOBB on the top
One 12" VOBB and one 6" VOBB in the middle
One 18" VOBB on the bottom
The regular 8" x 8" x 16" CMU were off the shelf block bought at a local retailer. The mortar joints were made by Sean Riggs of Stork so that a professional job would be completed. Likewise, it was chosen to use this method so that there would be no lack of independence from the VOBB or conflict of interest in the test results.
| Test # 1: 3/8" rebar in VOBB with two cavities filled |
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| Test # 2: 3/8" rebar in VOBB with three cavities filled |
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| Test # 3: 1/2" rebar in VOBB with two cavities filled |
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| Test # 4: 1/2" rebar in VOBB with three cavities filled |
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| Test # 5: 5/8" rebar in VOBB with two cavities filled |
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| Test # 6: 5/8" rebar in VOBB with three cavities filled |
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| Test # 7: regular 8" x 8" x 16" CMU with no rebar |
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