Nominal width of unit in.( mm) * 1, 2
Minimum face-shell thickness in.( mm)
Minimum web thickness in.( mm)
3( 76) and 4( 102) 3 / 4( 19) 3 / 4( 19) 6( 152) 1( 25) 3 / 4( 19)
8( 203) and greater 1-1 / 4( 32) 3 / 4( 19)
1 Adapted from ASTM C90- 22 Table 1. 2 Average of measurements on three units when measured as described in Test Methods C140.
CMU
construction can be reinforced whereby reinforcing bars are placed vertically in cells filled with grout to create a composite section analogous to reinforced concrete. If all cells, both unreinforced and reinforced are filled with grout, the CMU construction is referred to as fully grouted CMU. If only the reinforced cells are grouted, the CMU construction is referred to as partially grouted. If none of the cells are grouted, the CMU construction is referred to as ungrouted or hollow. Horizontal reinforcement may be placed in a wall via a bond beam or lintel, which is always grouted. Ladder reinforcement may also be placed in the mortar bed between courses.
Grout typically conforms to ASTM C476 and has a minimum compressive strength of 2,000 psi. Concrete masonry units have a compressive strength which may range from 1,250 psi to over 4,800 psi, although the maximum specified compressive strength of the assembled masonry will generally not exceed 3,000 psi. Both post-installed adhesive and mechanical anchors may be used in grouted CMU. If voids are present or suspected, mechanical anchors should not be used, and adhesive anchors should only be installed in conjunction with a screen tube to prevent uncontrolled flow of the bonding material. In hollow masonry, anchor strength is generally assumed to be based on the face shell thickness, which can be variable.
In the past, Hilti has provided technical data for 8” wide nominal CMU blocks. With the new criteria, Hilti has additional embedment depths which permit installation in wider walls, such as 10” or 12” nominal grouted CMU.
Clay brick
Clay brick is the most extensively used type of masonry unit throughout the world. Bricks are prismatic masonry units made from a suitable mixture of soil, clay, and a stabilizing agent( emulsified asphalt). They are shaped by molding, pressing, or extruding and are fired at elevated temperature to meet the strength and durability requirements of ASTM C62( solid brick) and ASTM C652 and ASTM C216( hollow brick).
Depending upon the grade, clay masonry bricks can have a compressive strength ranging from 1,250 psi to over 25,000 psi. Grouted multi-wythe masonry construction typically consists of two wythes, each one-unit masonry in thickness, separated by a space( collar joint) 1 / 2” to 4-1 / 2” wide, generally filled with grout. The wythes are connected with wall ties. This space may also be reinforced with vertical reinforcing bars. Solid clay brick masonry consists of abutting wythes interlaced with header courses. In general, adhesive anchors are recommended for use in clay brick. In older unreinforced masonry construction( URM) or where the condition of the masonry is unknown, it is advisable to use a screen tube to prevent unrestricted flow of the bonding material into voids. URM construction is not currently covered under the recent changes to AC01 and AC58.
Mortar
Mortar is used to provide uniform bearing between masonry units and to bond individual units into a composite assemblage that will withstand the imposed loading conditions. Mortar consists of a mixture of cementitious material, aggregate, and water proportionally combined in accordance with ASTM C270. Cement / lime mortar or masonry mortar( each in four types) are typically used under this standard.
Since mortar plays a significant role in the structural integrity of a masonry wall, it is important to understand how post-installed anchors interact with the structure. Within a masonry structure, there are designated joint locations, and the proximity of a postinstalled anchor to one of these locations must be considered in the design of the anchorage. Product specific guidelines are provided within this technical guide.
Grout
ACI defines grout as“ a mixture of cementitious material and water, with or without aggregate, proportioned to produce a pourable consistency without segregation of the constituents.” The terms“ grout” and“ mortar” are frequently used interchangeably but are not the same. Grout need not contain aggregate( mortar contains fine aggregate), is supplied in a pourable consistency( mortar is not), and fills voids( mortar only bonds elements together).
In summary, grout is used to fill spaces or cavities and provide continuity between building elements. In some applications, grout will act in a structural capacity, such as in unreinforced masonry construction.
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