When bagged cement is used, the field mix proportions are usually given in terms of designated amounts of fine and coarse aggregate per bag of cement. The amount of material that is mixed at a time is called a batch.
The size of a batch is usually designated by the number of bags of cement it contains, such as a four-bag batch, a six-bag batch, and so forth.
The process of weighing out or measuring out the ingredients for a batch of concrete is called batching.
When mixing is to be done by hand, the size of the batch depends upon the number of persons available to turn it with hand tools. When mixing is to be done by machine, the size of the batch depends upon the rated capacity of the mixer. The rated capacity of a mixer is given in terms of cubic feet of mixed concrete, not of dry ingredients. On large jobs, the aggregate is weighed out in an aggregate batching plant (usually shortened to “batch plant”).
Photo: Author: ConcreteBatchPlants ; licensed under the Creative Commons Attribution 3.0 Unported license
A batch plant also known as batching plant or concrete plant, a, is a device that combines various ingredients to form concrete. Some of these inputs include sand, water, aggregate (rocks, gravel, etc.), fly ash, potash, and cement.
Video explaining concept of Batching Plant
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A concrete plant can have a variety of parts and accessories, including but not limited to: mixers (either tilt-up or horizontal or in some cases both), cement batchers, aggregate batchers, conveyors, radial stackers, aggregate bins, cement bins, heaters, chillers, cement silos, batch plant controls, and dust collectors (to minimize environmental pollution).
The center of concrete batching plant is the mixer. There are three types of mixer, Tilt, pan, and twin shaft mixer. The twin shaft mixer can ensure even mixture of concrete and large output, while the tilt mixer offers a consistent mix with much less maintenance labor and cost.
Automation and controls
Modern concrete batch plants (both ready mix and central mix,) employ computer aided control to assist in fast, accurate measurement of input constituents or ingredients, as well as tie together the various parts and accessories for coordinated and safe operation. With concrete performance so dependent on accurate water measurement, systems will often use moisture probes to measure the amount of water that is part of the aggregate (sand and rock) material while it is being weighed, and then automatically compensate the mix design water target.
Video: A look inside a Batching Plant
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There are two types of concrete Batching Plants:
- Ready Mix Plants &
- Central Mix Plants
A Ready Mix Plant combines all ingredients except for water at the concrete plant. This mixture is then discharged into a ready mix truck (also known as a concrete transport truck). Water is then added to the mix in the truck and mixed during transport to the job site.
A Central Mix Plant combines some or all of the above ingredients (including water) at a central location. The final product is then transported to the job site.
A temporary batch plant is similar to the central batch plant but it can be constructed on a large job site. A concrete plant becomes central mix with the addition of a concrete mixer.
Mobile batching plants are nowadays increasing becoming popular for smaller volume and/or relatively short duration works.
Video: Mobile Batching Plant
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