Figure 3-16.Mobile concrete mixer plant.
The use of transit mixers on construction projects impose traffic problems that must be considered. Caution must be used during backing of the transit mixer. Backing should be controlled by a signalman, positioned so the operator can clearly observe the directions given. Extreme caution must be used when traveling over uneven terrain on a construction site. The stability of the mixer is greatly reduced with the extra weight of the concrete in the mixer unit. In such cases, a slow speed is recommended.
Some additional safety precautions that must be enforced are as follows:
1. Secure the discharge chute properly, using the lock provided.
2. Check to make certain other personnel are in the clear before starting the mixer charging or discharging.
3. Make sure the mixer is stopped before making any adjustments.
Precast and tilt-up construction is the fabrication of structural members or panels at a place other than its final position of use. It can be done anywhere, although these procedures are best adapted to a factory or prefab yard. Jobsite precasting is not uncommon for large projects. Precast concrete can be produced in several different shapes and sizes, including piles, girders, and roof members. Prestressed concrete is especially well-adapted to precasting techniques.
Tilt-up concrete is a special type of precast concrete in which the units are tilted up and placed, using cranes or other types of lifiing devices.
Wall construction, for example, is frequently done with precast wall panels originally cast horizontally (sometimes one above the other) as slabs. This method has many advantages over the conventional method of casting in place in vertical wall forms. Since a slab form requires only edge forms and a single surface form, the amount of formwork and form materialsContinue Reading