Masonry Magazine July 1974 Page. 20
Concrete Building Brick
(ASTM C 55)
Calcium Silicate Face Brick
(Sand-Lime Brick)
(ASTM C 73)
Where hollow units are used, units having two or three cores may be used; however, the former are more popular because the larger cells better facilitate the placement of steel and grout. Other unit shapes commonly used in reinforced concrete masonry wall construction are: bond beam units (for use in conjunction with horizontal steel reinforcement) and open-end units (for use in placing around vertical steel reinforcing bars).
Mortar
Mortar should comply with the requirements of "Mortar and Grout for Reinforced Masonry (ASTM C 476)." Table 1 lists the proportion requirements of this specification.
Grout
Grout for use in reinforced concrete masonry should also conform to ASTM Specifications (C 476) and should be proportioned within the limits given in Table 2. The choice of fine or coarse grout depends mainly on the minimum horizontal cross-sectional dimensions of the space to be grouted. In general, the smallest space to be grouted should be at least 2 x 3 inches. In such spaces, fine grout (with sand aggregate) should be used. When the minimum horizontal dimension of the space is 4 in., coarse grout (with pea gravel) should be used. If the minimum dimensions of the grout space exceed 5 to 6 in., such as in pilasters or columns, the cavities can be filled with conventional concrete with a maximum aggregate size of 1 in. The choice of grout type (and maximum size of aggregate) should be consistent with the particular job conditions to insure satisfactory placement of the grout and proper embedment of the reinforcement.
Table 3 may be used to estimate the required volume of grout in reinforced concrete masonry walls.
Reinforcement
Steel reinforcement should comply with the following specification requirements for concrete reinforcement:
Deformed Billet-Steel Bars
(ASTM A 615)
Rail-Steel Deformed Bars
(ASTM A 616)
Axle-Steel Deformed Bars
(ASTM A 617)
Prefabricated joint reinforcement should contain wire conforming to ASTM A 82 (Cold-Drawn Steel Wire).
Protection and Storage of Materials
Concrete masonry units should be protected against wetting prior to use and should be free from soil, ice, and frost when laid in the wall.
Steel reinforcement, metal ties and anchors should be kept free of oil and dirt, heavy or loose rust and other coatings that will destroy or reduce bond.
Cementitious materials should be stored under cover in a dry place.
Construction Layout
Masonry work should not begin until the horizontal and vertical alignment of the foundations has been checked and is satisfactory. Checking the horizontal layout of the wall (or other construction) by first laying out the units without mortar is also desirable and may help avoid unnecessary masonry unit cutting at windows, doors, pilasters, etc.
Steel reinforcing dowels should be in the proper location and of the specified size and length. If a foundation dowel does not line up with a vertical core, it may be bent if the maximum slope of the bent bar does not exceed one horizontal in six vertical. Dowels should be grouted into a core in vertical alignment, even though it is in an adjacent cell to the vertical wall reinforcement.
Mortar
Mortar materials should be properly measured (by volume or weight) so that the specified proportions are accurately controlled and maintained.
A one-cubic foot box is a useful device to determine and periodically check the proper number of shovelfulls of sand. In general, the mix should not be less than a multiple of full sacks of cement.
Mortar mixing should be done in a mechanical mixer with about one-half of the water and sand placed into the mixer first. Cementitious materials, color (if any) and the remaining water and sand should then be added and mixed for not less than 5 minutes. Hand mixing should not be used unless specifically approved by the architect or engineer.
Workability or consistency of mortar on the board should be such that the mortar is sufficiently wet or plastic to be worked properly with a trowel. Mortar which has stiffened due to evaporation may be retempered. Retempering on mortar boards should be done only by adding water within a basin formed with the mortar and the mortar reworked into the water. Any mortar which has begun to "set" or is not used within two and one-half hours after initial mixing should be discarded.
Grout
Grout materials should be accurately proportioned and mixed in a manner as previously described for mortar. Cement content of grout usually ranges from about 6 to 8 bags of portland cement per cubic yard of grout. Grouts placed by pump have cement contents near the higher end of the range.
All grout should be mixed to a fluid consistency; that is, it should be fluid as possible without segregation of the materials. When the slump is measured in accordance with ASTM C 143 (Method of Test for Slump of Portland Cement Concrete), the desired slump is about 8 in. for low absorption units and up to 10 in. for units with high absorption.
Laying Masonry Units
Prior to laying the first course of concrete masonry units, the top surface of the concrete foundation should be clean and free of laitance, loose aggregate and other materials that would