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Glossary

for CMU

ADMIXTURES - Materials added to cement, aggregate and water such as water repellents, air-entraining or plasticizing aids, pigments, or aids to retard or speed up setting.

AGGREGATES - Inert particles such as sand, gravel, and rock, which when bound together with cement and water, form concrete.

ANCHOR TIES - Any type of fastener used to secure masonry veneer to a support backing, such as another wall, usually for tension value.

ASTM - American Society for Testing and Materials.

AREAS -
Bedded Area - The area of the surface of a masonry unit which is in contact with mortar in the plane of the joint.
Gross Area - The total cross-sectional area of any plane encompassed by the outer periphery of any specified section.
Net Area - The gross cross-sectional area at any plane minus the area of ungrouted cores, notches, cells, unbedded areas, etc. Net area is the actual surface area of a cross-section of masonry.

BOND -
Adhesion Bond - The adhesion between masonry units and mortar or grout.
Mechanical Bond - Units laid so that they lap over each other in successive courses. Includes quarter bond, third bond and half or common bond.
Running Bond - Lapping of units in successive courses so that the vertical head joints lap. Placing vertical mortar joints centered over the unit below is called center bond, or half bond, while lapping 1/3 or 1/4 is called third or quarter bond.
Stack Bond - A bonding pattern where no unit overlaps either the one above or below. All head joints form a continuous vertical line. Also called plumb joint bond, straight stack, jack bond, jack on jack, and checker board bond.

BOND BEAM - One or more courses of masonry units poured solid and reinforced with longitudinal reinforcing bars. (See Bond Beam Block under CONCRETE MASONRY UNIT.)

CELL (Core) - The molded open space in a concrete masonry unit.

CHASE - A continuous recess built into a wall to receive pipes, ducts, etc.

CLEANOUT - An opening at the bottom of a grout space of sufficient size and spacing to allow the removal of debris.

CMACN - Concrete Masonry Association of California and Nevada.

COLLAR JOINT - The vertical longitudinal joint between wythes of masonry.

COMPOSITE MASONRY - Multiwythe masonry members acting together as a single member in resisting loads.

COMPRESSIVE STRENGTH - The maximum load required to fracture the masonry unit by applying a compressive force to the upper and lower surface of the unit. Expressed as either gross compressive strength, or net compressive strength. (See Strengths, CMU Basics)

CONCRETE MASONRY UNIT - (See Configurations, CMU Basics)
A-Block - A hollow unit with one end closed and the opposite end open. Term often used for fence unit as a support for 4 inch wide wall. Also called open end block.
Bond Beam Block - A hollow unit with portions of end and cross webs formed to permit a continuous channel for horizontal reinforcing steel and grout. Also called channel block.
Concrete Block - A concrete masonry unit made from portland cement and suitable aggregates with or without the inclusion of other materials.
H-Block - A hollow unit with a single cell in center of unit with both ends open. Used as a fence pilaster to support 4 inch wide wall.
Hollow Masonry Unit - A masonry unit whose net cross-sectional area in every plane parallel to the bearing surface is less than 75 percent of the gross cross-sectional area in the same plane.
Lintel Block - A hollow unit to permit the forming of a continuous channel for reinforcing steel and grout.
Open End Block - A hollow unit with one end closed and the opposite end open. A Double Open End unit has both ends open.
Pilaster Block- Concrete masonry units designed for use in construction of plain or reinforced concrete masonry pilasters and columns.
Sash Block - Concrete masonry unit which has an end slot for use in openings to receive metal window frames and pre- molded expansion joint material.
Scored Block - Block with grooves to provide patterns, as for example, to simulate raked joints. Sill Block - A solid concrete masonry unit used for sills or openings.
Solid Masonry Unit - Refers to concrete masonry units in which the vertical cores are less than 25 percent of the cross-sectional area.

COURSE - A continuous horizontal layer of masonry units.

DIMENSIONS - (See Dimensions and Sizes, CMU Basics)
Actual Dimensions - The measured dimensions of a designated item; for example, a designated masonry unit or wall, as used in the structure. The masonry unit or wall,as used in the structure. The actual dimension shall not vary from the specified dimension by more than the amount in the appropriate material standard.
Nominal Dimensions - Generally equal to its specified dimensions plus the thickness of the joint with which the unit is to be laid.
Specified Dimensions - The dimensions specified for the manufacture or construction of masonry, masonry units, joints or any other component of a structure. Unless otherwise stated, all calculations shall be made using or based on specified dimensions.

EFFLORESCENCE - A whitish powder resulting from the deposition of soluble salts on the surface of masonry, concrete, or soil.

FACE SHELL - The side wall of a hollow concrete masonry unit.

FACED WALL - A wall in which the facing and backing are so bonded or otherwise tied as to act as a composite element. As opposed to VENEER.

f'm - the specified compressive strength of masonry at the age of 28 days. (See Strengths, CMU Basics)

GROUT - A concrete mixture of sand, pea gravel (usually), water and sometimes admixture, which is poured or pumped into the vertical cells and bond beams. Grout encases the reinforcing steel and adds to the strength and fire rating of a block wall.

GROUT LIFT - The height to which grout is placed in a cell, collar joint, or wythe without intermission.

GROUT POUR - The total height of masonry wall to be poured prior to the erection of additional masonry. A pour may consist of one or more lifts.

JOINTS -
Bed Joint - The mortar joint that is horizontal at the time the masonry units are placed.
Dry Joint - A mortarless joint.
Head Joint - The mortar joint between units in the same wythe, usually vertical.
Struck Joint - Any mortar joint which has been finished with the trowel.

JOINT REINFORCEMENT - Steel wire, bar or prefabricated reinforcement which is placed in mortar bed joints.

JOINTING - The process of finishing mortar joints with a tool. Also called tooling.

LIME -
Hydrated Lime - Quicklime treated with only enough water to satisfy its chemical demand. Packaged in powdered form, does not require slaking.

MASONRY - Construction of building units bonded together with mortar, grout, or other accepted methods.

Reinforced masonry - Masonry construction in which reinforcement acts in conjunction with the masonry to resist forces.

MODULAR DIMENSION - A dimension based on a given module, usually eight (8) inches in the case of concrete block masonry.

MORTAR - A plastic mixture of cementitious materials, fine aggregate and water, with or without the inclusion of other specified materials.

PILASTER - An integral portion of the wall which projects on one or both sides and acts as a vertical beam, a column, an architectural feature, or any combination thereof.

POINTING - Filling mortar into a joint after the masonry unit is laid.

PRISM - Units mortared together, generally in stack bond, forming a wallette or assemblage to simulate "in wall construction", grouted per specification requirements. This is the standard test sample for determination of f'm.

REBAR - Reinforcing steel bars of various sizes and shapes used to strengthen masonry.

SHELL - The outer portion of a hollow masonry unit as placed in masonry.

TEMPER - To moisten mortar and re-mix to the proper consistency for use. Also called retempering.

TOOLING - See JOINTING.

TUCK POINTING - The filling in with fresh mortar of cut-out or defective mortar joints.

VENEER - A masonry facing which is attached to the backup but not so bonded as to act with it under load. As opposed to FACED WALL.

WALLS -
Bonded Walls - A wall in which two or more of its wythes of masonry are adequately bonded together to act as a structural unit.
Hollow-Unit Masonry Wall - That type of construction made with hollow masonry units in which the units are laid and set in mortar.

WALL TIE - A mechanical fastener which connects wythes of masonry to each other or to other materials.

WEB - An interior solid portion of a hollow masonry unit as placed in masonry.

WYTHE - The portion of a wall which is one masonry unit in thickness. Also called a tier. A collar joint is not considered a wythe.

CMU Basics - Glossary