CONCRETE BATCHING PLANTS
There are many classification standards for concrete plants. Concrete Plant can be divided into dry mix plant and wet mixing plant depending on whether a central mixer is used. It can be also divided into stationary concrete plant and mobile concrete plant depending on whether can be moveable.
Wet mix Concrete Plant
A Wet mix Concrete Plant, combines some or all of the above ingredients (including water) at a central location into a Concrete Mixer - that is, the concrete is mixed at a single point, and then simply agitated on the way to the jobsite to prevent setting (using agitors or ready mix trucks) or hauled to the jobsite in an open-bodied dump truck. Dry mix differ from Wet mix plants in that Wet Mix contain a central mixer whereas dry, which can offer a more consistent mixture in a shorter time (generally 5 minutes or less). Dry mix plants typically see more break strength standard deviation and variation from load to load because of inconsistencies in mix times, truck blade and drum conditions, traffic conditions, etc. With a Central Mix plant, all loads see the same mixing action and there is an initial quality control point when discharging from the central mixer. Certain plants combine both Dry and Wet characteristics for increased production or for seasonality.A Mobile batch plant can be constructed on a large job site.
Stationary Concrete Plant
The stationary concrete plant is designed for produce high-quality concrete. It has the advantages of large output, high efficiency, high stability and high specification. Stationary Concrete Batching Plant adopts reliable and flexible , it easy to maintenance and owning a low failure rate. It is widely used in various projects such as roads and bridges, ports, tunnels, dams and buildings.
Mobile Concrete Plant
The mobile batch plant, also known as a portable concrete plant is a very productive, reliable and cost effective piece of equipment to produce batches of concrete. It allows the user to batch concrete at most any location then move to another location and batch concrete. Portable plants are the best choice for temporary site projects or even stationary locations where the equipment height is a factor or the required production rate is lower.
Dry mix Concrete Plant
A Dry mix Concrete Plant, also known as Transit Mix Plant, weighs sand, gravel and cement in weigh batchers via digital or manual scales .
All the ingredients then are discharged into a chute which discharges into a truck. Meanwhile, water is either being weighed or volumetrically metered and discharged through the same charging chute into the mixer truck. These ingredients are then mixed for a minimum of 70 to 100 revolutions during transportation to the jobsite.
A concrete plant, also known as a batch plant or batching plant or a concrete batching plant, is equipment that combines various ingredients to form concrete. Some of these inputs include water, air, admixtures, sand, aggregate (rocks, gravel, etc.), fly ash, silica fume, slag, and cement. A concrete plant can have a variety of parts and accessories, including: mixers (either tilt drum 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.
The heart of the concrete batching plant is the concrete mixer, and there are many types of mixers such as Tilt Drum, Pan, Planetary, Single Shaft and Twin shaft mixer. The twin shaft mixer can ensure an even mixture of concrete through the use of high A Pan or Planetary mixer is more common at a precast plant. Aggregate bins have 2 to 6 compartments for storage of various sand and aggregate (rocks, gravel, etc.) sizes, while cement silos are typically one or two compartments, but at times up to 4
compartments in a single silo. Conveyors are typically between 24-48 inches wide and carry aggregate from the ground hopper to the aggregate bin, as well as from the aggregate batcher to the charge chute.
The aggregate batcher also named as aggregate bins, is used for storage and batch the sand, gravel and crushed stone of the concrete plant. There are also many types of aggregate batchers, but most of them measured aggregate by weighing, some use the weighing hopper, some use the weighing belt.
The cement silos are an indispensable device in the production of concrete. It mainly stores bulk cement, fly ash, mineral powder and others. There are 3 types of cement silos, bolted cement silos, Horizontal cement silos and integrated cement silos. Integrated cement silos made in factory, it can be used directly. Bolted cement silo bolted for easy installation and removal. Horizontal cement silos have lower requirements on foundations and can be transported by truck or flatbed without disassembly.
The screw conveyor is a machine to transfer the materials from the cement silos to the powder weighing hopper.
Concrete plant use the control system to control the working of the machine. concrete batch plants employ computer aided control to assist in fast and accurate measurement of input constituents or ingredients. With concrete performance so dependent on accurate water measurement, systems often use digital scales for cementitious materials and aggregates, and moisture probes to measure aggregate water content as it enters the aggregate batcher to automatically compensate for the mix design water/cement ratio target. Many producers find moisture probes work well only in sand, and with marginal results on larger sized aggregate.
A centralized concrete batching plant can serve a large space.
The plants are situated in areas for industrial use and supply trucks can serve residential districts or inside cities.
Better quality concrete is produced.
Elimination of storage space for basic materials on site.
Elimination of hiring of plant and machinery.
The wastage of basic materials is avoided.
Workers associated with the production of concrete are eliminated.
The time required is greatly reduced.
Noise and dust pollution on the site is reduced.
DISADVANTAGES OF CONCRETE BATCHING PLANTS:
Materials from central plant and mixing begins at that plant, so the travel time is crucial over long distances.
The access road and site access must be not able to carry a greater load of ready-mix trucks.
It has limited-time between mixing and curing of the concrete is 210 minutes of batching.
APPLICATION OF BATCHING PLANTS:
In Ready Mix:
A concrete plant also known as ready mix concrete plant is usually located inside the city and concrete is transported to the site by a concrete truck mixer.
Ready-mixed concrete plants are required for the durability, reliability, safety and environmental protection of concrete plant systems.
In Precast Applications:
Precast concrete is a concrete product that is processed in a homogeneous process in the manufacturing unit.
How does the Concrete mixing plant works
Concrete mixing plant is divided into four parts: gravel feed, powder (cement, fly ash, bulking agents, etc.) to feed, water and feed additives, transmission and storage stirred their workflow shown in Figure 1. , the mixer control system power, into the human – machine dialogue operation interface, system initialization process, including recipe number, grade concrete slump, producers, etc. according to the amount of weight carried on each silo, weighing hoppers. detection, output material or material empty full signal, prompting the operator to determine whether to activate the control program starts stirring sand, stone belt motor fed into the metering hopper; open fly ash, cement tank valve, start the electromechanical screw conveyor ash cement to the metering hopper; open water reservoir and control valves admixture pool water and additives into the metering hopper metered meet the set requirements doo door open metering, mixing the ingredients into the mixer within already started to set. time to open the mixer door, into the concrete mixer had received material.
There are two types of concrete batching plants:
Ready mix concrete plants :
A ready mix concrete 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.
Central mix plants :
A central mix concrete 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. Central mix plants differ from ready mix plants in that they offer the end user a much more consistent product, since all the ingredient mixing is done in a central location and is computer-assisted to ensure uniformity of product.
The concrete batch plants can be categorized into 4 parts:
1- Aggregate feeding,
2- Powder feeding (fly ash, cement and expanding agent),
3- Water and
4- Admixture for mixing the materials, conveyance and storag
When the control system of mixer is connected to an electricity source, the operation interface of the man-machine interaction will appear and system will begin to process initialization which includes the formula number, concrete slump, concrete grade and productivity.
Each silo and weighing hopper is tested according to weighing system. Its control system will output the signal of the amount of material to prompt the operator to decide whether to start the control program or not.
The belt conveyor is initiated to transmit the aggregate to the weighing hopper; the valve of the fly ash and cement tank should be opened and the screw conveyor and motor initiated to transmit them into the weighing hopper;
The control valve of the water sump and admixture sump needs to be opened to make water and admixture flow into the weighing hopper.
Once the weight of all material types meets the needs of specific amounts, the door of the weighing hopper is opened automatically.
The materials will then be mixed by a concrete mixer. Once the setting time is over, the loading door of the concrete mixer opens and the concrete flows into a concrete mixer trucks.
This process is conducted very carefully since concrete must not segregate and also because the concrete must be ready and transported and then used before its preliminary setting time which is between 30-45 minutes.In some countries, this is carried out by a mobile concraete batching machine.
The Difference between Twin Shaft and Single Shaft Concrete Mixer
Concrete mixer mixes various raw materials, and then producing different types of concrete products that are needed in lots of construction works. It is said that concrete mixers play a vital role in concrete mixing plant and lots of construction projects. Here we want to find the key differences of twin shaft and single shaft concrete mixer.
The difference in driving system
The driving system of single shaft concrete mixer is the chain transmission structure, and in contrast, twin shaft concrete mixer adopts V type belt and sliding gear structure. Comparing with single shaft concrete mixer, twin shaft concrete mixer has low working noises, convenient operation and high reliability, which has wide application in large concrete batching plants.