Concrete a mixture of Portland cement, sand, gravel, and water is used for many types of construction projects. These range from small jobs such as patios and floors to huge dams or miles of roadway. Concrete masons place and finish the concrete for these projects. They also may color concrete surfaces, expose aggregate (small stones) in walls and sidewalks, or fabricate concrete beams, columns, and panels.
Terrazzo workers create attractive walkways, floors, patios, and panels by exposing marble chips and other fine aggregates on the surface of finished concrete. Much of the preliminary work of terrazzo workers is similar to that of concrete masons.
In preparing a site for placing concrete, masons set the forms for holding the concrete to the desired pitch and depth and properly align them. They then direct the casting of the concrete and supervise laborers who use shovels or special tools to spread the concrete. Masons then guide a straightedge back and forth across the top of the forms to screed (level) the freshly placed concrete.
Immediately after leveling the concrete, masons carefully smooth the concrete surface with a long-handled tool about 8 by 48 inches (called a bull float) to cover coarser materials and bring a rich mixture of fine cement paste to the surface.
After the concrete has been leveled and floated, finishers 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. They use a special tool (called a groover) to make joints or grooves at specific intervals that help control cracking.
Next, finishers trowel the surface with a powered trowel or by hand with a small, smooth, rectangular metal tool. This troweling removes most imperfections and brings the fine cement paste to the surface.
As the final step, masons retrowel the concrete surface back and forth with powered and hand trowels to create a smooth finish. For a coarse, nonskid finish, 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.
On concrete surfaces that will remain exposed after forms are stripped, such as columns, ceilings, and wall panels, concrete masons cut away high spots and loose concrete with hammer and chisel, fill any large indentations with a Portland cement paste and smooth the surface with a rubbing 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.
Attractive, marble-chip terrazzo requires three layers of materials. First, concrete masons or terrazzo workers build a solid, level concrete foundation that is 3 to 4 inches deep. After the forms are removed from the foundation, workers place a 1-inch deep mixture of sandy concrete. Before this layer sets, terrazzo workers partially embed metal ferrule strips into the concrete wherever there is to be a joint or change of color in the terrazzo. These strips separate the different designs and colors of the terrazzo panels and help prevent cracks. For the final layer, terrazzo workers blend and place a fine marble chip mixture that may be color-dyed into each of the panels, then hand trowel each panel until it is level with the tops of the ferrule strips. While the mixture is still wet, workers toss additional marble chips of various colors into each panel and roll a lightweight roller over the entire surface.
When the terrazzo is thoroughly dry, helpers grind it with a terrazzo grinder (somewhat like a floor polisher, only much heavier). Slight depressions left by the grinding are filled with a matching grout material and hand troweled for a smooth, uniform surface. Terrazzo workers then clean, polish, and seal the dry surface for a lustrous finish.
Improved materials, equipment, and tools are making concrete masons and terrazzo workers more productive.
Concrete or terrazzo work is fast paced and strenuous. Since most finishing is done at floor level, workers must bend and kneel a lot. Many jobs are outdoors, but work is generally halted during rain or freezing weather. To avoid chemical burns from uncured concrete and sore knees from frequent kneeling, many workers wear kneepads. Workers usually wear water-repellent boots while working in wet concrete.
Concrete masons and terrazzo workers held about 100,000 jobs in 1992; terrazzo workers accounted for a very small proportion of the total. Most concrete masons work for concrete contractors or for general contractors on projects such as highways, bridges, shopping malls, or large buildings such as factories, schools, and hospitals. A small number are employed by firms that manufacture concrete products. Most terrazzo workers work for special trade contractors who install decorative floors and wall panels.
About 1 out of 17 concrete masons and terrazzo workers is self-employed, a smaller proportion than in other building trades. Most self-employed masons specialize in small jobs, such as driveways, sidewalks, and patios.
Concrete masons and terrazzo workers learn their trades either through on-the-job training as helpers or through 2- or 3-year apprenticeship programs. Many masons first gain experience as construction laborers.
On-the-job training programs consist of informal instruction from experienced workers in which helpers learn to use the tools, equipment, machines, and materials of the trade. They begin with tasks such as edging and jointing and using a straightedge on freshly placed concrete. As they progress, assignments become more complex, and trainees usually can do finishing work within a short time.
Two- and 3-year apprenticeship programs, usually jointly sponsored by local unions and contractors, provide on-the-job training in addition to a recommended minimum of 144 hours of classroom instruction each year. A written test and a physical exam may be required. In the classroom, apprentices learn applied mathematics, plan reading, and safety. Apprentices generally receive special instruction in layout work and cost estimating.
When hiring helpers and apprentices, employers prefer high school graduates who are at least 18 years old, in good physical condition, and licensed to drive. The ability to get along with others also is important because concrete masons frequently work in teams. High school courses in shop mathematics and blueprint reading or mechanical drawing provide a helpful background.
Experienced concrete masons or terrazzo workers may advance to supervisors or contract estimators. Some open their own concrete contracting businesses.
Employment of concrete masons and terrazzo workers is expected to grow more slowly than the average for all occupations through the year 2005. In addition to job openings that will stem from the rising demand for the services of these workers, other jobs will become available as experienced workers transfer to other occupations or leave the labor force.
The demand for concrete masons and terrazzo workers will rise as the population and the economy grow. More masons will be needed to build highways, bridges, subways, factories, office buildings, hotels, shopping centers, schools, hospitals, and other structures. In addition, the increasing use of concrete as a building material particularly in nonresidential construction will add to the demand. More concrete masons also will be needed to repair and renovate existing highways, bridges, and other structures. Employment of concrete masons and terrazzo workers, however, will not keep pace with the demand for these construction projects because of rising productivity resulting from improved materials, equipment, and tools. Greater use of improved concrete pumping systems, quicker setting cement, troweling machines, prefabricated masonry systems, and other timesaving technologies are enabling concrete masons and terrazzo workers to work more efficiently.
Employment of concrete masons and terrazzo workers, like that of many other workers, is sensitive to ups and downs in the economy. Workers in these trades can experience periods of unemployment when the level of nonresidential construction falls. On the other hand, shortages of these workers may occur in some areas during peak periods of building activity.
According to the limited information available, average hourly earnings including benefits for concrete masons who belonged to a union and worked full time ranged between $15 and $37 in 1992. Concrete masons in Boston, New York, San Francisco, Los Angeles, Philadelphia, and other large cities received the highest wages. Nonunion workers generally have lower wage rates than union workers. Apprentices usually start at 50 to 60 percent of the rate paid to experienced workers.
Concrete masons often work overtime, with premium pay, because once concrete has been placed, the job must be completed.
Annual earnings of concrete masons and terrazzo workers may be lower than the hourly rates suggest because bad weather and downturns in construction activity can limit the time they can work.
Many concrete masons and terrazzo workers belong to the Operative Plasterers' and Cement Masons' International Association of the United States and Canada, or to the International Union of Bricklayers and Allied Craftsmen. Some terrazzo workers belong to the United Brotherhood of Carpenters and Joiners of the United States.
Concrete masons and terrazzo workers combine skill with knowledge of building materials to construct buildings, highways, and other structures. Other occupations involving similar skills and knowledge include bricklayer, form builder, marble setter, plasterer, stonemason, and tilesetter.
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Reprinted with Permission of U. S. Department of Labor