Types of Batching Plants

Guess what those big ugly things are not all the same. Some are small and ugly while others are bigger and uglier and they all comes in f\different shapes and sizes(literally). <will type this later>.

Concrete Batching Plants:

Concrete batching plants, as the name suggests, produce concrete in batches. They take in cement, water,sand, coarse aggregates amd admixtures to produced concrete. The average batching plant has three main systems working in it:

1. The material storage unit: This includes the bins for storing sand, cement, aggragates, silos for cement etc.
2. The conveyance unit: This all important part conveys the raw materials to the mixer for mixing.
3. The mixer: This mixes(what else do you think it will do?) the raw materials to produce concrete.

Given below is the diagram of a typical batching plant. While the design may change, the basic layout is the same.

The storage system:

This system stores the cement, fine aggregates(sand), coarse aggregates(gravel, limestone, gypsum) and also generally has a tank for storing compressed air for cleaning and another tank for storing chemical additives for the concrete mix.

The various types of storage system present are:

A plant with bins(grey structures)

1. Bin type:        Consists of a metal structure with partitions inside for storing the materials except the chemicals, air and the cement. Depending on the type of the batching plant, the bins greatly vary in size. They drop materials onto a conveyor belt or directly into a movable bucket( called skip bucket/charger box) via pneumatically or electrically operated gates that open for specific time periods so that appropriate amounts of materials are added for different concrete recipes. They are common in large capacity plants(ie plants with capacities over 60 cu m per hour). The bins may be arranged in-line or side-by-side.

Star Batcher

2. Star Type:       This system consists of the materials(except cement) stored in the open with partitions between the materials. The aerial view roughly resembles half a star so hence the name. The partitions are made of metal, concrete blocks or bricks. They are fed into a bucket for transporting to the mixer by means of a scraper( the long arm attached to the cabin) which has a bucket attached and is controlled by an operator in the cabin. The number of partitions depends on the requirement but is generally at least four.

Compartment bins:                  Very similar to the bins mentioned above but the difference is that while the bins generally feed onto a conveyor that feeds the skip bucket, the compartment bins feed directly into the skip-bucket. They are more common in small capacity and vertical plants.


Along with the baove, a typical plant has an air tak to store compressed air, tank for admixture chemicals and silos for storing cement.



Conveyance Unit( Sigh, i typed it and this stupid computer shut down, wait shall type the whole thing  again).

1. Skip-bucket/Charger-box:   This is a large steel box that receives the aggregates and transports it to the mixer for mixing. The box runs on rails pulled by 1 or 2 metal cables which are attached to a motor or two motors. The box has steel rails to run along the track but polyurethane wheels are increasily becoming popular due to their longer life and quieter operation.


2. Conveyor belts:                 Made of Buna-S or EP rubber they are used to convey materials from the bins to the skip-bucket or to the mixer. A modified form of the conveyor belt is called a dip-bucket and it is used to carry materials to the mixer in place of the charger box. The dip-bucket consists of two protective rubber layers at the sides to prevent spillage and the belt is partitioned to ensure correct quantities are batched.

3. Screw Conveyors:              Screw conveyors are used to carry cement from the silios to the mixer.

4. Others:                                A batching plant also has a network of pipes to carry air-suspended oil droplets for circulation and for operating the various pneumatic systems like batching gates etc. A water pump for addign water. Admixture pump for adding the chemical additives from the admixture tank.  

Concreting Producing Machines

While driving by a construction site, if you probably thought 'yuck!!! what is that ugly thing' you were probably looking at a concrete-mixer.

There are several types of concrete each with it's production process. For this article I shall focus on Pre-cast concrete, site-mixed concrete and Ready Mixed Concrete.

Concrete is made by mixing cement, fine aggregates(sand), aggregates(a coarse mix of small rocks/crushed gravel , limestone or granite), water and chemical additives.

The oldest form of mixing concrete is to take some poor sod, give him all the above mentioned stuff(other than maybe the chemicals), give him a big vessel and something to stir it all with. This was the Australopithecus stage of concreting. The next stage came when the concrete mixer was invented.

A small site-mixer

Site Mixer:     


Also called a cement mixer, it is basically a rotating bucket. Initially muscle-powered, electric and diesel models were eventually developed. Except for some very small projects, this is almost obsolete in most of the developed world although there is still considerable,but declining, demand for it in the developing countries. They shall be explained in detail in a separate section.
                                                   

A large capacity mixing plant loading concrete
into truck-mixers

Concrete Mixing Plants:

The most popular method of production of concrete, these plants produce concrete in batches or continuously.  These plants comprise of a cement and aggregate storage unit, a mixer, water storage units and conveyance units. These vary from truck or trailer mounted units to large capacity plants that resemble buildings.

A mobile plant mounted on a trailer

For more information see the section on batching plants( hold it, I have to type it!!!)

What are concreting machines?

A concrete boom pump placing
concrete fed from a truck-mixer

To put it simply, concreting machines are the machines that make concrete. I will not go into concrete in this post and focus only on concreting equipment. The machines range from small, man-portable concreting spraying pumps that plaster the walls and floors of your home to apartment-block sized machines that produce concrete. 

Concreting machines can be broadly classified into four categories:-

1. Machines that make concrete: ie Concrete batching plants, site mixers etc.
2. Machines that transport concrete: ie Transit Mixers ( the ugly drums mounted on trucks that cause traffic snarls)
3. Machines that place concrete: concrete pumps, distributors etc
4. Machines that recycle concrete.

 From the next post onwards, we shall see about concreting machines in the order given above.

Welcome

Hello,
Concrete and concreting equipment are all around us, but few of us(except those in construction) notice them. Fewer still, know about the machinery used and the amazing innovations and the technology that goes into it. This blog has been created with a view to educate people about those equipment and provide a platform for beginners as well as professionals to exchange views and knowledge.

GK Thondulkar