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COPY RIGHT PLCM692 APPRENTICESHIP.ORG
Plasterers And Cement Masons
CRAFTMANSHIP PROSPERITY RESPONSIBILITY
You will learn this trade by attending the apprenticeship program. Required classroom training of 160 hours per year combined with accumulating 5000 hours of on-the-job training satisfies the program requirement that promotes you to Journeyperson status. Like many other construction trades, these workers may experience reduced earnings and layoffs during downturns in construction activity. Cement masons often work overtime, with premium pay, because once concrete has been placed, the job must be completed.
Cement masons work with concrete, one of the most common and durable materials used in construction. Once set, concrete-a mixture of Portland cement, sand, gravel, and water-becomes the foundation for everything from decorative patios and floors to huge dams or miles of roadways.
Cement masons place and finish the concrete. They also may color concrete surfaces; expose aggregate (small stones) in walls and sidewalks; or fabricate concrete beams, columns, and panels. In preparing a site for placing concrete, cement masons first set the forms for holding the concrete and properly align them. They then direct the casting of the concrete and supervise laborers who use shovels or special tools to spread it. Masons then guide a straightedge back and forth across the top of the forms to "screed," or level, the freshly placed concrete. Immediately after leveling the concrete, masons carefully smooth the concrete surface with a "bull float," a long-handled tool about 8 by 48 inches that covers the coarser materials in the concrete and brings a rich mixture of fine cement paste to the surface.
After the concrete has been leveled and floated, cement masons press an edger between the forms and the concrete and guide it along the edge and the surface. This produces slightly rounded edges and helps prevent chipping or cracking. Cement masons use a special tool called a "groover" to make joints or grooves at specific intervals that help control cracking. Next, they trowel the surface using a powered and/or hand trowel, a small, smooth, rectangular metal tool.
Sometimes, cement masons perform all the steps of laying concrete, including the finishing. As the final step, they retrowel the concrete surface back and forth with powered and hand trowels to create a smooth finish. For a coarse, nonskid finish, cement masons brush the surface with a broom or stiff-bristled brush. For a pebble finish, they embed small gravel chips into the surface. They then wash any excess cement from the exposed chips with a mild acid solution. For color, they use colored premixed concrete or color hardener. On concrete surfaces that will remain exposed after the forms are stripped, such as columns, ceilings, and wall panels, cement masons cut away high spots and loose concrete with (power) hammer and chisel, fill any large indentations with a Portland cement paste, and smooth the surface with a carborundum stone. Finally, they coat the exposed area with a rich Portland cement mixture, using either a special tool or a coarse cloth to rub the concrete to a uniform finish.
Throughout the entire process, cement masons must monitor how the wind, heat, or cold affects the curing of the concrete. They must have a thorough knowledge of concrete characteristics so that, by using sight and touch, they can determine what is happening to the concrete and take measures to prevent defects.