Copyright Goodheart-Willcox Co., Inc. Chapter 3 Tools and Equipment 45 Safety Note The concrete joint saw must be handled carefully to avoid injury from flying particles. When operating a concrete saw, safety glasses and ear protection must be worn. When sawing concrete dry, a respirator or approved dust mask must be worn because the dust that is created contains silica, which is a health hazard. 3.3.9 Hand and Power Floats Hand floats are used to prepare concrete surfaces for trow- eling. The floats are made from wood, aluminum, magne- sium, cork, or molded rubber. They range in size from 10″ to 18″ long and 3 1/8″ to 4 1/2″ wide. See Figure 3‑50. Some floats are powered by electricity or gasoline en- gines. They have a rotating disk about 2′ in diameter that performs the same task as the hand float. 3.3.10 Vibrating Tools for Concrete Concrete vibrators are tools that masonry contractors use to aid in removing air pockets or voids in concrete that has been placed in walls, floors, footings, or other types of concrete forms. The use of a concrete vibrator will aid in reducing voids or air pockets that can occur in or next to the concrete form. These pockets or voids are visible when the forms are removed from the con- crete structure. A concrete vibrator moves or oscillates in such a way that it consolidates the concrete into a uniform mass. Operating a concrete vibrator is simple. Once the de- vice is turned on, the head of the shaft is fed into the fresh concrete and allowed to move down through the concrete. After reaching the appropriate depth, the shaft is raised and moved to the next location to per- form the operation again as needed until the concrete in the structure has adequately been vibrated. Handheld Concrete Vibrators Figure 3‑51A shows an electric flex shaft handheld concrete vibrator. Handheld concrete vibrators oper- ate on 115 V electrical power. The vibrating head in this model has a red rubber coating the head can also be purchased in a steel version. Flexible shafts can be purchased in lengths from 2′ to 21′, depending on the need or application of the concrete project. Figure 3‑51B shows a high-frequency concrete vi- brator. This model is a compact vibrator controlled by an all-electronic circuitry in the control box. The head diameter is 2.2″ and approximately 15″ in length. The shaft is approximately 16′ in length. The head weight is 11.2 lb and the total weight of the unit is approxi- mately 35 lb. Trade Tip Never over-vibrate the concrete, as it will segregate sand, gravel, and crushed stone in the mixture. Over-vibrating will also separate water from the concrete mix. Safety Note When operating a concrete vibrator, it is important to wear ear protection because of the vibration noise the device emits. Average decibels may be 85 or higher depending on the device, the manufacturer, and the material being vibrated. Wear waterproof hand protection because the chemicals in the concrete can cause burns to the skin. Safety glasses or goggles are necessary because the cement slurry can cause burns to the eyes. A B C Marshalltown Company Figure 3‑50. Hand floats are made from various materials, including wood, aluminum, and cork. A—A 3 1/2″ × 16″ redwood float with a wood handle. B—A 3 3/4″ × 12″ magnesium float with a soft grip handle. C—A 3 1/8″ × 16″ magnesium float with a soft grip handle. This float has rounded edges, which help keep the trowel from gouging into the concrete that has been floated.