lower strength than concrete . The behavior of the masonry components , as well as the geometry of their cavities and webs , has a considerable influence on the ultimate load capacity of the fastening .
2.1.3.1 CONCRETE BLOCK
Concrete block is the term which is commonly used to refer to concrete masonry units ( CMU ) made from Portland cement , water and mineral aggregates . CMUs are manufactured in a variety of shapes and sizes using normal weight and lightweight aggregates . Both hollow and solid load bearing CMUs are produced in accordance with ASTM C90 .
Nominal width of unit in . ( mm )
Minimum face-shell thickness A in . ( mm )
Minimum web thickness A in . ( mm )
3 ( 76 ) and 4 ( 102 ) 3 / 4 ( 19 ) 3 / 4 ( 19 ) 6 ( 152 ) 1 ( 25 ) 1 ( 25 ) reinforcing may be placed in the wall via a bond beam , 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 compressive strength of at least 2,000 psi . Concrete masonry units have a compressive strength that may range from 1,250 to over 4,800 psi , although the maximum specified compressive strength of the assembled masonry will generally not exceed 3,000 psi .
2.1.3.2 MORTAR
Mortar is the product that is used in the construction of reinforced and non-reinforced unit masonry structures . The role of mortar when hardened in the finished structure is to transfer the compressive , tensile and shear stresses between the units . Mortar consists of a mixture of cementitious material , aggregate and water combined in accordance with ASTM C270 . Either a cement / lime mortar or a masonry mortar , each in four types , can be used under this specification .
|
8 ( 203 ) 1-1 / 4 ( 32 ) 1 ( 25 )
10 ( 254 ) 1-3 / 8 ( 35 ) 1-1 / 8 ( 29 )
|
Mortar |
Type |
Average compressive strength at 28 days , min psi ( MPa ) |
1-1 / 4 ( 32 ) B ≥12 ( 305 ) 1-1 / 2 ( 38 ) 1-1 / 8 ( 29 )
1-1 / 4 ( 32 ) B
Adapted from ASTM C90 .
A Average of measurements on three units taken at the thinnest point .
B This face-shell thickness is applicable where the allowable design load is reduced in proportion to the reduction in thickness from the basic face-shell thickness shown .
CMU sizes generally refer to the nominal width of the unit ( 6- , 8- , 10-inch , etc .). Actual dimensions are nominal dimensions reduced by the thickness of the mortar joint .
16 "
Nominal size ( usually fictitious )
8 "
8 "
Modular size ( actual )
7 5 / 8 "
15 5 / 8 "
7 5 / 8 "
Concrete block construction can be reinforced , whereby reinforcing bars are placed vertically in the cells and those cells are filled with grout to create a composite section analogous to reinforced concrete . If all cells , both unreinforced and reinforced , are filled with grout , the construction is referred to as fully grouted . If only the reinforced cells are grouted , the construction is referred to as partially grouted . Horizontal
Cement-lime M 2500 ( 17.2 ) S 1800 ( 12.4 ) N 750 ( 5.2 ) O 350 ( 2.4 )
Masonry cement M 2500 ( 17.2 ) S 1800 ( 12.4 ) N 750 ( 5.2 ) O 350 ( 2.4 )
Since mortar plays a significant role in the structural integrity of the masonry wall , it is important to understand how poweractuated fasteners interact with the structure . Within a masonry structure there are designated joint locations . The proximity of a power-actuated fastener to one of these locations must be considered in the design of the fastening . Product specific guidelines are provided within this manual .
2.1.3.3 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 , in actuality , not the same . Grout need not contain aggregate ( mortar contains fine aggregate ). Grout is supplied in a pourable consistency where mortar is not . Grout fills voids while mortar bonds elements together .
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