Editing Concrete block (section)

==Sizes and structure==

Blocks come in modular sizes, with the most popular typically referred to (by their thickness) as "4-inch", "6-inch", "8-inch", and "12-inch". In the US, concrete blocks are nominally {{convert|16|in|mm|abbr=on}} long and {{convert|8|in|mm|abbr=on}} wide.  Their actual dimensions are {{convert|3/8|in}} less than the nominal dimensions (to allow for {{frac|3|8}}-inch mortar joints between blocks in any orientation).<ref>{{Cite web|url=https://www.archtoolbox.com/materials-systems/masonry/concblocksizes.html|title=Concrete Block (CMU) Sizes, Shapes, and Finishes|website=Archtoolbox.com}}</ref> In Ireland and the UK, blocks are usually {{convert|440|x|215|x|100|mm|in|abbr=on}} excluding mortar joints. In Australia, New Zealand and Canada,<ref>{{Cite book |last=Sturgeon |first=Gary |title=Coursing Tables, Metric Shapes and Sizes |publisher=Canadian Concrete Masonry Producers Association |pages=2 |language=en}}</ref> blocks are usually {{convert|390|x|190|x|190|mm|in|abbr=on}} excluding mortar joints.

Block cores are typically tapered so that their top surface (as laid) has a greater surface on which to spread a mortar bed and for easier handling. Most concrete blocks have two cores, but three- and four-core units are also produced. A core also allows for the insertion of [[rebar|steel reinforcement]] to span courses in order to increase [[tensile strength]].  This is accomplished by [[grout]]ing the voids of blocks containing rebar with concrete. Thus reinforced, concrete block walls are better able to resist lateral forces such as [[wind load]] and seismic forces.{{sfn|Beall|1987|pages=61–63}} Cores may also be filled with [[expanded-polystyrene]] (EPS) block foam insulation, substantially increasing the [[R-value (insulation)|R-value]] of the resulting wall to be in compliance with the US national energy code.<ref>{{Cite web|title=EPS Insulation {{!}} Geofoam, Styrofoam, EPS & Polystyrene {{!}} Universal Foam Products|url=https://universalconstructionfoam.com/products/styrofoam-eps-insulation/#concrete_block_insulation|access-date=2020-10-26|website=universalconstructionfoam.com}}</ref>

A variety of specialized shapes exist to allow special construction features.  U-shaped blocks, or knockout blocks, have notches to allow the construction of [[bond beam]]s or [[lintel]] assemblies, using horizontal reinforcing grouted into place in the cavity. Blocks with a channel on the end, known as "jamb blocks", allow doors to be secured to wall assemblies. Blocks with grooved ends permit the construction of [[Expansion joint|control joints]], allowing a filler material to be anchored between the un-mortared block ends. Other features, such as radiused corners known as "[[bullnose]]s", may be incorporated. A wide variety of decorative profiles also exist.{{sfn|Beall|1987|pages=66-68}}

Concrete blocks may be formulated with special aggregates to produce specific colors or textures for finish use. Special textures may be produced by splitting a ribbed or solid two-block unit; such factory-produced units are called "split-rib" or "split-face" blocks.{{sfn|Beall|1987|pages=68-70}} Blocks may be scored by grooves the width of a mortar joint to simulate different block modules. For example, an {{convert|8|by(x)|16|in|adj=on}} block may be scored in the middle to simulate {{convert|8|by(x)|8|in|adj=on}} masonry, with the grooves filled with mortar and struck to match the true joints.<ref name=ching1>{{cite book|last=Ching|first=Francis D.K.|title=A Visual Dictionary of Architecture|year=2012|publisher=[[John Wiley & Sons]], Inc.|isbn=978-0-470-64885-8|edition=2nd|page=168}}</ref>