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Central Mixer

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Construction Equipment
Mining Equipment

A central mixer, also known as a concrete mixer, is a portable mixing plant used for producing large quantities of concrete. The concrete is mixed and prepared at a central mixing plant, which involves several stages to ensure the quick, cheap, and efficient production of concrete. It can also be used to produce ready-mix concrete and to produce products deriving from concrete.

Also known as portable mixing plants, central mixers have all the equipment to produce concrete in large volumes for a relatively inexpensive cost, including aggregate bins, cement silos, conveyors, and loading equipment. They also include water tanks and equipment used to control the amount of water that is dispatched into the concrete batch. Batchers are used to weigh, control, and record the amount of concrete that is being mixed and are normally positioned between the storage bins, silos, and tanks. Dust collection systems are routinely installed in the facility to reduce the loss of cement as well as eliminate dust around the cement and fly ash silos.

The central mixing plant is designed as such so that it can easily be transported from one site to the next. Consisting of anywhere from two to four parts, the central mixer can reach as high as 14 feet (4.3 m) and as wide as 12 feet (3.7 m). By mounting it on rubber tires, it is able to travel even on highways, but a special permit is required. The typical central mixer can travel at 30 cubic yards (23 m3) per hour. Some plants make use of tractors and other vehicles that are capable of moving at faster speeds.

[edit] History

Central mixing plants were originally met with skepticism, but some manufacturers went ahead and produced them. The original and older versions required the help of a crane to hoist them. Most of the newer modifications are produced with a built-in hoisting system or hydraulic jacks that reduce the amount of time required for erecting the plant to half a day.[1] Other configurations involve a crane or derrick with a clamshell bucket that can dump materials directly into the storage bin. Other plants make use of a conveyor belt or screw conveyor to transport the concrete.

When central mixing was established, the skepticism surrounding it quickly dissolved and was replaced with a huge demand from manufacturers. The central plant was efficient, cheap, and portable, and reduced the amount of physical labor involved in the process. The task usually involves no more than a superintendent to monitor the operation, a crane operator, a mixer operator, one worker to feed aggregate to the bucket conveyor, one to measure the amount of aggregate to be disposed of in the mixer, one to clean out the cars, and two to handle the cement.

Central mixing is also a stronger method for preparing concrete. Concrete can be transported up to five miles (8 km) without losing its strength or affecting its weather-resistant capabilities.

The biggest downfall with central mixing occurs from delivering large volumes of concrete. The care and costs associated with transporting large amounts of concrete can be demanding and it is usually recommended to use a smaller fleet of vehicles to do so.[2]

[edit] References

  1. Day, David A. and Benjamin, Neal B.H. Construction Equipment Guide. Wiley: 1991
  2. Central Mixing Plants for Concrete. The Ohio Engineer. 2008-09-08