Figure 8-28.-Masonry wall horizontal joint reinforcement.

Both piers and pilasters are used to support heavy, concentrated vertical roof or floor loads. They also provide lateral support to the walls. Piers and pilasters offer an economic advantage by permitting construction of higher and thinner walls. They may be constructed of special concrete masonry units (figure 8-27) or standard units.

REINFORCED BLOCKWALLS

Block walls may be reinforced vertically or horizontally. To reinforce verdically, place reinforcing rods (called rebar) into the cores at the specified spacing and till the cores with a relatively high-slump concrete. Rebar should be placed at each corner and at troth sides of each opening. Vertical rebar should be spaced a maximum of 32 inches on center in walls. Where splices are required, the bars should be lapped 40 times the bar diameter. The concrete should be placed in one continuous pour from foundation to plate line. A cleanout block maybe placed in the first course at every rebar stud for cleaning out excess mortar and to ensure proper alignment and laps of rebars.

Practical experience indicates that control of cracking and wall flexibility can be achieved with the use of horizontal joint reinforcing. The amount of joint reinforcement depends largely upon the type of construction. Horizontal joint reinforcing, where required, should consist of not less than two deformed longitudinal No. 9 or heavier cold-drawn steel wires. Truss-type cross wires should be 1/8-inch diameter (or heavier) of the same quality. Figure 8-28 shows joint reinforcement on 16-inch vertical spacing. The location and details of bond beams, control joints, and joint reinforcing should all be shown on the drawings.

PATCHING AND CLEANING BLOCK WALLS

Always fill holes made by nails or line pins with fresh mortar and patch mortar joints. When laying concrete masonry walls, be careful not to smear mortar on the block surfaces. Once they harden, these smears cannot be removed, even with an acid