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 wash, nor will paint cover them. Allow droppings to dry and harden. You can then chip off most of the mortar with a small piece of broken concrete block (figure 8-29, view 1) or with a trowel (view 2). A final brushing of the spot removes practically all the mortar (view 3).

RETAINING WALLS

The purpose of a retaining wall is to hold back a mass of soil or other material. As a result, concrete masonry retaining walls must have the structural strength to resist imposed vertical and lateral loads. The footing of a retaining wall should be large enough to support the wall and the load of the material that the wall is to retain. The reinforcing must be properly located as specified in the plans. Provisions to prevent the accumulation of water behind retaining walls should be made. This includes the installation of drain tiles or weep holes, or both.

PAINTING CONCRETE MASONRY

Several finishes are possible with concrete masonry construction. The finish to use in any specific situation should be governed by the type of structure in which the walls will be used and the climatic conditions to which they will be exposed.

Paints now commonly used on concrete masonry walls include portland cement paint, latex paint, oil-based paint, and rubber-based paint. For proper application and preparation of the different types of paint, refer to the plans, specifications, or manufacturer's instructions.

Figure 8-29.-Cleaning mortar droppings from a concrete block wall.

Figure 8-30.-Names of brick surfaces.

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