Masonry Magazine July 1974 Page. 21
Prevent the mortar or grout from achieving satisfactory bond. The first course should be laid in a full mortar bed (mortar coverage on face shells and webs) except that the cell areas to be grouted should be kept free from mortar so the grout will have direct contact and bond to the foundation.
As masonry units are laid, they should be aligned to form an unobstructed, continuous series of vertical spaces within the wall. Spaces that will contain vertical reinforcement should be at least 2 inches wide. Hollow units should be laid with full mortar coverage on horizontal and vertical face shells except that webs should also be bedded where they are adjacent to cells to be reinforced and filled with grout or concrete. If the wall is to be solidly grouted, then none of the cross webs need to be mortared since it is desirable for the grout to flow laterally. Solid units should be laid with full head and bed joints. Where no bond pattern is indicated on the drawings or in the specifications, masonry units should be laid in running bond (alternate vertical joints aligned).
Excess mortar should be prevented from extruding from the joints and falling into spaces to be grouted. Mortar that projects more than 3/8 in. into the grout space should be removed because such protrusions may restrict the flow of grout and cause the grout to bridge at these locations.
Unless otherwise specified, horizontal and vertical face joints should be 3/8 in. thick and should be tooled when thumbprint hard with a round (or V-shaped) bar to produce a dense, slightly concave surface well bonded to the block at the edges. Mortar joints in surfaces to be plastered, stuccoed, or covered with other masonry should be cut or struck flush. Joints which are not tight at the time of tooling should be raked out, pointed with fresh mortar, and then re-tooled.
Reinforcement.
Horizontal reinforcement is placed as the walls are laid up. Usually, conventional steel bar reinforcement is used and placed in bond beam courses built with bond beam units or standard units with portions of the cross webs removed. Expanded metal lath, placed in the mortar joint immediately under each bond beam course, prevents filling of the vertical cells below the bond beam not intended to be filled (Figure should be 1/4 in. and not less than one 1).
Joint reinforcement may be used in place of, or in conjunction with, reinforcement in bond beams to provide the required area of horizontal reinforcement. Longitudinal wires of prefabricated joint reinforcement should be located over face-shell mortar beds and be fully embedded in mortar for their entire length with minimum mortar cover of 5/8 in. from the exterior wall face. Where longitudinal wires are lapped, the minimum lap should be 6 in. In 1/2 in. horizontal mortar joints, 1/4 in. bars may be used; and in 3/8 in. joints, wires should be No. 6 gage or smaller.
Vertical steel reinforcement may be erected before the masonry units are laid, or it may be dropped into position after laying is completed. If steel is erected prior to block laying, open-end, A-shaped units should be used so that the units can be easily placed around the reinforcing steel. When vertical steel is placed after wall erection, the bars should be held in proper position at the top and bottom and at intervals not exceeding 192 bar diameters to prevent displacement during grouting (Figure 1). Where required, lapped splices should provide sufficient lap to transfer the working stress of the reinforcement by bond and shear. The minimum lap should be 30 bar diameters.
The minimum clearance of vertical reinforcing steel from the masonry bar diameter between bars.
Bolts, anchors and other inserts which attach adjoining construction should be bedded in mortar joints (where possible) and held in proper position until the wall is grouted. Sometimes such bolts and anchors can be either wired to the reinforcing bars or held with a wood template fastened to the wall surface to keep them from being displaced during the grouting operation.
Grouting.
There are two grout placement procedures in general use: (1) low-lift grouting, where the grout is placed in lifts up to 4 ft. in height, and no cleanouts are required; and (2) high-lift grouting, where the walls are laid up full height before grouting and cleanout holes are required at the bottom of each grout space containing vertical reinforcement.
Low-lift grouting requires no special concrete block shapes or equipment. The wall is built to scaffold height, or to a bond beam course, but not more than 4 ft. Steel reinforcing bars are placed in the proper block cells and the cells are grouted. The level of grout is stopped about 1-1/2 in. from the top of masonry in order to form a key with the succeeding grout pour. Grout spaces containing reinforcement should be puddled or
FIGURE 1-TYPICAL REINFORCED CONCRETE MASONRY CONSTRUCTION USING THE LOW-LIFT GROUTING TECHNIQUE
Vertical steel-Lap 30 bar diameters at splices; hold in position at intervals of 192 diameters.
Place metal lath under bond beam to confine grout.
Steel in Bond Beams is set in place as wall is laid up.
Floor Slab.
Footing.
Place grout in lifts not to exceed four feet; puddle or vibrate in place.
Place mortar on cross webs adjacent to cells which will be grouted to prevent leakage.
Cells containing steel are filled solidly with grout; vertical cells should provide a continuous cavity, free of mortar droppings, and at least 2 x 3 inches in size.