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Other mason's tools and equipment include shovels, mortar hoes, wheelbarrows, chalk lines, plumb bobs, and a 200-foot ball of good-quality mason's line. Be sure to keep wheelbarrows and mortar tools clean; hardened mortar is difficult to remove. Clean all tools and equipment thoroughly at the end of each day or when the job is finished. A mortar mixing machine (figure 8-3) is used for mixing large quantities of mortar. The mixer consists primarily of a metal drum containing mixing blades mounted on a chassis equipped with wheels for towing the machine from one job site to another. The mixer is powered by either an electric motor or a gasoline engine. After mixing, the mortar is discharged into a mortar box or wheelbarrow, usually by tilting the mixer drum. As with any machine, refer to the manufacturer's operator and maintenance manuals for proper operation. Be sure to follow safety requirements related to mixer operations. CONCRETE MASONRY LEARNING OBJECTIVE: Upon completing this section, you should be able to identify the components and requirements of concrete masonry construction. One of the most common masonry units is the concrete block. It consists of hardened cement and may be completely solid or contain single or multiple hollows. It is made from conventional cement mixes and various types of aggregate. These include sand, gravel, crushed stone, air-cooled slag, coal cinders, expanded shale or clay, expanded slag, volcanic cinders (pozzolan), pumice, and "scotia" (refuse obtained from metal ore reduction and smelting). The term "concrete block" was formerly limited to only hollow masonry units made with such aggregates as sand, gravel, and crushed stone. Today, the term covers all types of concrete block-both hollow and solid-made with any kind of aggregate. Concrete blocks are also available with applied glazed surfaces, various pierced designs, and a wide variety of surface textures.
Figure 8-3.-Mortar mixing machine Although concrete block is made in many sizes and shapes (figure 8-4) and in both modular and nonmodular dimensions, its most common unit size is 7 5/8 by 7 5/8 by 15 5/8 inches. This size is known as 8-by-8-by-16-inch block nominal size. All concrete block must meet certain specifications covering size, type, weight, moisture content, compressive strength, and other characteristics. Properly designed and constructed, concrete masonry walls satisfy many building requirements, including fire prevention, safety, durability, economy, appearance, utility, comfort, and acoustics. Concrete blocks are used in all types of masonry construction. The following are just a few of many examples: Exterior load-bearing walls (both below and above grade); Interior load-bearing walls;
Figure 8-4.-Typical unit sizes and shapes of concrete masonry units. Fire walls and curtain walls; Partitions and panel walks; Backing for brick, stone, and other facings; Fireproofing over structural members; Fire safe walls around stairwells, elevators, and enclosures; Piers and columns; Retaining walls; Chimneys; and Concrete floor units. There are five main types of concrete masonry units: 1. Hollow load-bearing concrete block; 2. Solid load-bearing concrete block; 3. Hollow nonload-bearing concrete block; 4. Concrete building tile; and 5. Concrete brick. Load-bearing blocks are available in two grades: N and S. Grade N is for general use, such as exterior walls both above and below grade that may or may not be exposed to moisture penetration or weather. Both grades are also used for backup and interior walls. Grade S is for above-grade exterior walls with a weather-protective coating and for interior walls. The grades are further subdivided into two types. Type I consists of moisture-controlled units for use in arid climates. Type II consists of nonmoisturecontrolled units.
Figure 8-4.-Typical unit sizes and shapes of concrete masonry units-Continued. |
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