Cement masons, concrete finishers, and terrazzo workers all 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 and concrete finishers place and finish 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 to place 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 float it—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, concrete 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. Concrete finishers use a special tool called a "groover" to make joints or grooves at specific intervals that help control cracking. Next, they smooth the surface using either a powered 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 or 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 the forms are stripped, such as columns, ceilings, and wall panels, cement 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 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.
Segmental pavers lay out, cut, and install pavers—flat pieces of masonry made from compacted concrete or brick. This masonry is typically installed in patios, sidewalks, plazas, streets, crosswalks, parking lots, and driveways. Installers usually begin their work on a previously prepared base that has been graded to the proper depth, although some projects may include the base preparation. A typical segmental paver installation begins with leveling a layer of sand, followed by placement of the pavers, normally by hand but sometimes by machine. Usually the work includes constructing edges to prevent horizontal movement of the pavers. Sand is then added to fill the joints between the pavers.
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 cement masons. There are six different types of terrazzo, but the focus of this description is on the most common standard terrazzo: Marble-chip terrazzo, which requires three layers of materials. First, cement masons or terrazzo workers build a solid, level concrete foundation that is 3 to 4 inches deep. Second, after the forms are removed from the foundation, workers add a 1-inch layer of sandy concrete. Terrazzo workers partially embed, or attach with adhesive, metal divider strips in the concrete wherever there is to be a joint or change of color in the terrazzo. For the third and final layer, terrazzo workers blend and place into each of the panels a fine marble chip mixture that may be color-pigmented. While the mixture is still wet, workers add additional marble chips of various colors into each panel and roll a lightweight roller over the entire surface.
When the terrazzo is thoroughly set, helpers grind it with a terrazzo grinder, which is somewhat like a floor polisher, only much heavier. Any 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.
Work environment. Concrete, segmental paving, or terrazzo work is fast-paced and strenuous, and requires continuous physical effort. Because most finishing is done at floor level, workers must bend and kneel often. Many jobs are outdoors, and work is generally halted during inclement weather. The work, either indoors or outdoors, may be in areas that are muddy, dusty, or dirty. To avoid chemical burns from uncured concrete and sore knees from frequent kneeling, many workers wear kneepads. Workers usually also wear water-repellent boots while working in wet concrete.
Most workers work 40 hours a week, although the number of hours can be increased or decreased by outside factors. Earnings for workers in these trades can be reduced on occasion because poor weather and slowdowns in construction activity limit the time they can work.
| 1. | Check the forms that hold the concrete to see that they are properly constructed. |
| 2. | Set the forms that hold concrete to the desired pitch and depth, and align them. |
| 3. | Spread, level, and smooth concrete, using rake, shovel, hand or power trowel, hand or power screed, and float. |
| 4. | Mold expansion joints and edges, using edging tools, jointers, and straightedge. |
| 5. | Monitor how the wind, heat, or cold affect the curing of the concrete throughout the entire process. |
| 6. | Signal truck driver to position truck to facilitate pouring concrete, and move chute to direct concrete on forms. |
| 7. | Produce rough concrete surface, using broom. |
| 8. | Operate power vibrator to compact concrete. |
| 9. | Direct the casting of the concrete and supervise laborers who use shovels or special tools to spread it. |
| 10. | Mix cement, sand, and water to produce concrete, grout, or slurry, using hoe, trowel, tamper, scraper, or concrete-mixing machine. |
| 11. | Cut out damaged areas, drill holes for reinforcing rods, and position reinforcing rods to repair concrete, using power saw and drill. |
| 12. | Wet concrete surface, and rub with stone to smooth surface and obtain specified finish. |
| 13. | Wet surface to prepare for bonding, fill holes and cracks with grout or slurry, and smooth, using trowel. |
| 14. | Clean chipped area, using wire brush, and feel and observe surface to determine if it is rough or uneven. |
| 15. | Apply hardening and sealing compounds to cure surface of concrete, and waterproof or restore surface. |
| 16. | Chip, scrape, and grind high spots, ridges, and rough projections to finish concrete, using pneumatic chisels, power grinders, or hand tools. |
| 17. | Spread roofing paper on surface of foundation, and spread concrete onto roofing paper with trowel to form terrazzo base. |
| 18. | Build wooden molds, and clamp molds around area to be repaired, using hand tools. |
| 19. | Sprinkle colored marble or stone chips, powdered steel, or coloring powder over surface to produce prescribed finish. |
| 20. | Cut metal division strips, and press them into terrazzo base so that top edges form desired design or pattern. |
| 21. | Fabricate concrete beams, columns, and panels. |
| 22. | Waterproof or restore concrete surfaces, using appropriate compounds. |
| 23. | Install anchor bolts, steel plates, door sills and other fixtures in freshly poured concrete or pattern or stamp the surface to provide a decorative finish. |
| 24. | Apply muriatic acid to clean surface, and rinse with water. |
| 25. | Push roller over surface to embed chips in surface. |
| 26. | Polish surface, using polishing or surfacing machine. |
[Back to Top]