why do standard modular brick units have 3 holes in them?
why do standard modular brick units have 3 holes in them?
(OP)
I looked on the BIA website and didn't see anything...is it just to save weight?
thanks, just curious
thanks, just curious






RE: why do standard modular brick units have 3 holes in them?
Steve Wagner
RE: why do standard modular brick units have 3 holes in them?
Sorry, it probably has to do with the manufacture of these, it may be an extrusion process like for hollowcore slabs.
csd
RE: why do standard modular brick units have 3 holes in them?
seriously tho', i think to control shinkage sounds good; different question, how are they formed ? (dowels, cut out after the mound is filled ?)
RE: why do standard modular brick units have 3 holes in them?
Don Phillips
http://worthingtonengineering.com
RE: why do standard modular brick units have 3 holes in them?
RE: why do standard modular brick units have 3 holes in them?
Old clay bricks used shallow depressions top and bottom instead for both reasons. The shallow depressions were easy for manual casting. Modern bricks are extruded.
RE: why do standard modular brick units have 3 holes in them?
RE: why do standard modular brick units have 3 holes in them?
ASTM C 652 is the specification for hollow clay brick. A section in this standard deals with requiremens for hollow spaces (cores and cells).
In addition to lighteness and ease of handling, the use of hollow brick cuts down on costs associated with: manufacture (less energy, less material), transportation, construction etc...
As far as reinforcing goes, I am aware of single-wythe(leaf) reinforced clay masonry unit construction (using hollow clay blocks) but not reinforced single-wythe hollow clay brick construction. Has any research ever been done on the latter?
RE: why do standard modular brick units have 3 holes in them?
Even if you could get the bar through the holes the grout could not be relied on to provide adequate cover for durability. Or rather, the grout could be relied on to not provide adequate cover.
RE: why do standard modular brick units have 3 holes in them?
What I assumed were hollow clay block because of size, are actually classified as hollow clay brick.
So that means products like interstate brick's 8x8x16 Super Atlas have to comply with ASTM specification for hollow brick, C 652. Table 1 of this standard allows up to a maximum nominal width of 12 inches for Class H60V hollow brick.
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This means that some hollow clay brick are indeed manufactured for single wythe/leaf reinforced masonry constrution.
What I'd like to know is how horizontal reinforcement is placed when these large units are used? Is it restricted to joint reinforcing placed in bed joints...or can units be manufactured to look like concrete bond beam blocks...that allow horizontal bars to be placed on the cross webs?
RE: why do standard modular brick units have 3 holes in them?
Joint reinforcement is the most common type of reinforcement in the U.S. for clay brick/block. Depending on the size of the units, they can be sawed if some sort of bond beam is required. The most common manufacturing process for clay brick (extruding) does not easily permit shapes with recessed aeas. Concrete masonry is made using a different process (pressing), so units with recessed areas that may accept reinforcing steel are readily available.
In the U.S., much of the larger size clay brick/block has been replaced by 6x4x16 architectural concrete masonry units, but this is still a small portion of the brick market, which is mainly veneer.
In Europe, hollow clay block have commonly been used for many years. There, the size is much different, with 8", 10" or 12" thicknesses common and the units having many cores (4 to 12). These units are basic units used for bearing walls and floor systems and never for an architectural appearance.
There is really no such thing as a "standard" brick, considering the wide range of sizes made - there are only ASTM standards that are the minimums for physical properties and dimensional tolerence. - Almost any size or configuration can be specified.
With proper design, 6" concrete masonry walls are used be used for loadbearing masonry structures over of over 20 stories. All it takes is a good engineer, good specifications and good design codes like ACI 530. To bad all of these sophisticated buildings are common outside the U.S.
RE: why do standard modular brick units have 3 holes in them?
What if the clay raw material was blended to produce a low plasticity, dry pressed to produce shapes with recesses, dried (if necessary), and then fired etc? This may be uneconomical prudent for a manufacturer...but can a structurally sound clay bond beam unit be manufactured this way?
RE: why do standard modular brick units have 3 holes in them?
RE: why do standard modular brick units have 3 holes in them?
Like all ceramics, there is a lot of shrinkage and distortion during the firing (a toilet will shrink an inch or two). If you do not have symetry, you can easily get more distortion, splitting or cracking. I am not an expert on brick manufacturing, but have been involved in the masonry supply inducstry for many years.
P.S. - comparing unit hollow concrete block and brick strengths is like comparing apples and oranges. The orientation of the units and aspect ratios when tested are radically different.. Brick are tested flat (3 5/8" wide x 2 3/8" high) - something like a compression failure, while hollow block are tested with a width typically equal to the height (shear failure). The block minimum strength requirements are minimal (1900 psi on the net area), while I have made and tested hollow block at 8500 psi when I finally found a machine with enough capacity AND a thick enough platten that would not distort. Concrete cylinder testing equipment is not adequate.
RE: why do standard modular brick units have 3 holes in them?
RE: why do standard modular brick units have 3 holes in them?
The weight reduction savings on shipping would be negligible since brick are really not bought on price. Usually the key items are meeting specification or appearance.
Bending wall ties has nothing to do with with stability. The specifications control the properties of the mortar, but the masons will change it much quicker than any specification. If you are dealing with wall ties, you have a back-up wall that is already in place.
The configuration of brick is based on the historic performance of the materials and masons.
RE: why do standard modular brick units have 3 holes in them?
RE: why do standard modular brick units have 3 holes in them?
RE: why do standard modular brick units have 3 holes in them?
Bricklayers may complain because they have the right to. If solid or concrete brick are being used, the mortar must be mixed differently. ASTM has no real requirements for the amount of water in the mortar when the brick are laid. The key factor in mortar is not really strength, but workability, which relates to the product (material, shape and configuration) being used. ASTM recommends to use the weakest mortar possible to carry the load.
I know of a company that made concrete brick without either "frogs" or cores, so they were genuine "floaters" because of the shape and low initial rate of absorption of the concrete. The contractors complained until the price was reduced $0.005 per brick and then there were to complaints.
Masonry is very forgiving and is often based on habits - that is why it is the most common material for residential (one and multiple story buildings) wall construction in the developed world.
RE: why do standard modular brick units have 3 holes in them?
http://www.brickinfo.org/BIA/technotes/t41.htm
Bond beam units described by concretemasonry...where slots are cut at jobsite are shown in Fig 2. The slots can also be made at the plant..and is done after units have been fired.
RE: why do standard modular brick units have 3 holes in them?
The 2nd reason is it reduces the weight of the unit, taking less clay to make and saving costs (and less cost to ship).
The 3/4" dia. cored hole is too small for reinf, that's why there is "clay block" as I call it...or Hollow Clay Masonry. There are a few plants in North America that make these types of units...Interstate Brick (Utah), Mutual Materials (Washington state), Summit Brick (Colorado), Carolina Brick (North Carolina) and a Canadian company called IXL.
RE: why do standard modular brick units have 3 holes in them?
If a kerf were to be cut into the brick before firing, it would cause the unit to crack up. The clay mass needs to stay as balanced as possible (as rectangular as possible) for the unit not to crack up or turn into a "banana". The other reason why this can't be done is the manner of the extrusion process. Its much like a tube of toothpaste...where the brick comes extruded out in 8ft slugs. You can blade or kerf anything in that slug as long as it is continuous and to the slug (visulaize a tube of toothpaste and as you extrude it out, sticking a knife blade to it to create a cont. slot...the same holds true with brick manf.).
After the slug is cut, it goes onto a belt table and where wire blades (like a cheese cutter) cut it into the individual unit sizes. It is only at this step that a bond beam could only be cut or created and the orientation is just to impossible for any machine to get to.
With that said, Interstate did develop an open-ended unit that created kerf's during extrusion (and before the unit goes into the kiln) on the end face shell that could be popped out by a mason. This allows for full head joint construction by having an open end face (i.e., the orientation is an "A" shape).
RE: why do standard modular brick units have 3 holes in them?
Mike McCann
McCann Engineering