As with brick , CMUs have actual dimensions and nominal dimensions. The nominal dimension of a CMU is the actual dimension plus the width of the mortar joint. The nominal dimension works within the 4" grid that other construction materials follow. The graphic below shows the difference between nominal and actual sizes. They are identified by their depth — i. Concrete blocks also come in half-sizes, which are helpful in reducing the need to cut blocks in the field at corners or the end of walls.
The architect should always attempt to design buildings using the nominal dimensions to the nearest half-block size to reduce waste and labor due to cut blocks. The following table provides concrete block sizes in both nominal and actual dimensions.
While 4", 6", 8", 10", and 12" are the standard sizes, some manufacturers offer other sizes not listed below. The standards identify appropriate materials, compressive strength, dimensional tolerance, moisture absorption, and other performance characteristics.
Concrete brick is made from concrete similar to concrete block, but concrete bricks are fabricated in sizes that match traditional clay bricks i.
The weight of concrete masonry units varies depending on the density of concrete mix used. Lighter CMUs are less expensive, require less labor to install, and tend to have better fire resistance properties. Heavier units tend to reduce sound transmission, have much higher compressive strengths, and have greater thermal storage capacity; however, they are more expensive and cost more to install. Architects must specify the CMU weight if a particular weight is required.
The following table provides the ASTM standards that apply to concrete masonry units. This could be because of the quantity of materials going into the production, natural deviations in density, different end styles, etc.
Despite masonry standards , differences exist. For example, I bought the 8 x 8 x 16 block pictured above at Home Depot. Online they list the block as weighing 38 pounds, but when I put one on the scale, it weighed in at Regardless, for general knowledge, we can use the average weights for any building project calculations. This smaller, flatter block can be used for a variety of purposes, decorative and functional.
My intent was to use them for both, add 2 more inches to the wall of my fire pit and as a decorative capstone to cover the open-holed cinder blocks underneath. The standard 8 x 2 x 16 cinder block weighs 16 pounds on average 7. I put one on the scale and it came in at an even 18 pounds. Maybe not. Most cinder blocks are around the same size. Of course, there are exceptions of square cinder blocks, or cinder blocks that are used as pavers, and even extra-large cinder blocks. Cinder blocks are a type of concrete masonry block that uses a material called cinder.
These blocks are usually shaped like an eight when views from the top and are an efficient way to create construction blocks. The cinder in these blocks is the aggregate, with cement and sand paired with that aggregate.
Almost all cinder blocks are said to be 8-byby inches. However, like most boards, their actual measurements are slightly different than what the label states.
Most cinder blocks are a tiny bit smaller. This makes it much easier for masons to calculate how many blocks they need. It may not seem like much but when the building is multiple stories high, this could end up being hundreds of inches, or feet.
Another thing to remember is that cinder blocks usually have two large holes in them with a 1-inch divider between holes. We get this question a lot. Is a cinder block different than a concrete block or some other type of block like a cement block? Well, the short answer is that they are all concrete masonry units or CMUs. The only difference is that they have a different aggregate. Aggregate is coarse- to medium-grained particulate material used in construction.
It is the most mined material in the world, considering there are so many different types. This eliminates the need to lift units over the top of the reinforcing bar, or to thread the reinforcement through the masonry cores after the wall is constructed.
Bond beams in concrete masonry walls can be accommodated either by saw-cutting a portion of the webs out of a standard unit, or by using bond beam units. Horizontal bond beam reinforcement is easily accommodated in these units.
Lintel units are similar to bond beam units except the bottom of the unit is solid to confine grout to the lintel. Lintel units are available in various depths to carry appropriate lintel loads over door and window openings. Sash block have a vertical groove molded into one end to accommodate a window sash. Sash block can be laid with the grooves adjacent to one another to accommodate a preformed control joint gasket. An all-purpose or kerf unit contains two closely spaced webs in the center, rather than the typical single web.
This allows the unit to be easily split on the jobsite, producing two 8 in. Figure 3 shows units developed for specific wall applications. Control joint units are manufactured with one male and one female end to provide lateral load transfer across control joints. Bull-nosed units are available with either a single or double bull nose, to soften corners.
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