THE
TWO MOST IMPORTANT FACTS
ABOUT A REGULAR 8" x 16" CMU WALL
1.
The most expensive cost is the LABOR, not the materials
2. The weakest part
of the wall is the mortar joint
VOBB significantly reduces the cost of labor and "eliminates" the mortar
joint
1. The cost to dry-stack
an 18" VOBB block is less than 30 cents (note: this is the estimated "cost"
for a simple job - The sales price depends on if there is a contractor, his/her
insurance, scaffolds, electrical cut-outs, plumbing, etc.)
2. VOBB blocks
are dry-stacked and concrete slurry "grout" (with pea gravel) is pumped/poured
into the cavities
3. VOBB can be used for residential, commercial, agricultural,
retaining walls, hunting camps, at the beach, etc.
WHAT CAN HAPPEN TO REGULAR 8" x 8" x 16" CMU WITH ONLY A WEAK MORTAR JOINT
Whoops. I am sure glad that I did not spend my money on this!!!
Now the owner will have to both clean up the mess and to replace
the wall. Ouch!
One more example of a weak mortar joint with expensive labor
Here are some pictures of regular 8" * 16" CMU used to build an approximate three-foot high retaining wall. Due to having insufficient rebar and grout, these regular 8" * 16" failed. The wall was lacking in lateral strength, even though 8" wide CMU were used.
Weak mortar joint in a brick wall.
| Written in
October, 1974 (over thirty years ago) by Carl Haynes, Jr., P.E.
and J. W. Simons, P.E.
"Normally, concrete blocks are laid in mortar. Contrary to popular belief, the mortar does not act as a "glue" to hold the blocks together. It serves mainly as a bed to aid in leveling the blocks. Mortar joints have little, if any, strength in tension and relatively poor adhesion. For structural purposes other than direct compression, the strength of a mortar joint is negligible. Futhermore, mortar joints do not completely tighten the wall against the penetration of rain. The mortar joints actually serve as a capillary wicks and draw moisture through the cracks between the mortar and the blocks. Being extremely porous, the blocks themselves also soak up water. Accordingly, a concrete block wall laid in mortar must be waterproofed by the application of a sealing compound." http://mha-net.org/msb/docs/surfbond.PDF |
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