What is a Concrete Mixer?
A concrete mixer mixes cement, aggregates and water and produce concrete mechanically. There are various types of concrete mixers available which makes concrete production quick and economical.
Types of Concrete Mixers
There are two broad types of concrete mixers:
- Batch mixers
- Drum Types Mixer
- Tilting drum mixers
- Non-tilting drum mixer
- Reversing drum mixer
- Pan Type Mixer
- Drum Types Mixer
- Continuous mixers
Batch Concrete Mixers
Batch mixers are widely used machines for concrete mixing. Concrete mix obtained by this mixer is collected batch by batch and time by time. So, it is called as batch mixer.
After pouring all the materials into pan or drum, it mixes all of those for some time and finally discharges. This process is repeated until required amount of concrete mix is obtained.
In general Batch mixers are two types.
- Drum type mixers
- Pan type mixers
Drum Type Mixers
In case Drum type mixers concrete ingredients are mixed in a drum which is actually in double conical frustum shape.
Drum types mixers are classified into three types:
- Tilting drum mixers
- Non-tilting drum mixers
- Reversing drum mixers
Tilting Drum Mixers
Tilting drum mixer means the drum will discharge concrete by tilting downwards. It is rapid discharge process and used for larger projects. Rapid means it delivers concrete by gravity that is tilting the drum downwards because of this the concrete mix obtained will be not subjected to segregation.
Low workable concretes which contains large sized aggregates of size greater than 7.5cm are also mixed efficiently with this tilting type mixers.
But the mixing efficiency depends on some of the factors as follows:
- Shape of the drum
- Angle of the drum
- Size of blades
- Angle of blades
The only disadvantage of this mixer is sticking of concrete to bottom of drum. To overcome this a method called buttering of mixer is applied in which some amount of cement mortar is mixed in the mixer before mixing first batch of concrete.
Non-Tilting Drum Mixers
Non- tilting drum mixers are not allowed to tilt and the drum rotates about its horizontal axis. For the discharge of concrete a chute is arranged in inclined position which will receives the concrete mix from drum and discharges out.
In this case, the drum is opened at two ends and consists blades insides when materials are poured through one end and mix is collected through another end.
Rapid discharge of concrete is not possible in this case. Due to this delay, the concrete may be vulnerable to segregation.
The larger size aggregate is not discharged easily with the mix. So, size of aggregate mot more than 7.5cm is preferable for this type of mixers. So, this type of mixers are generally used for small projects.
Reversing Drum Mixers
Reversing drum mixers are similar to non-tilting type mixers but in this case reversal of rotation takes place for different action.
The drum has two openings, one end is for pouring materials and other end is for discharge of mix. The drum rotates about its horizontal axis. The rotation of drum takes place in one direction for mixing and in opposite direction for discharging.
Two different set of blades are arranged for mixing and discharging. They are suitable for dry concrete mixes.
Pan Type Concrete Mixers
Pan type mixers consists a circular pan in which concrete is mixed. The mixing is done by blades which are arranged in star shape inside the pan.
There are two types of pan mixers are available. In one case, the circular pan is constant and only star blades rotate about vertical axis of pan. In the other case, circular pan rotates while the blades are at static position.
But in both cases, the mixing is efficient and concrete mixture is collected through central hole provided in the pan. The rotating star blades contains special blades called scrapper blades which will make concrete not to stick to the pan.
The blades can also be adjusted in height so, there is no room for concrete to store in the pan. We can say among the all types of batch mixers pan type mixer are more efficient.
Continuous Concrete Mixers
Continuous mixer, the name itself telling its duty that the loading, mixing and discharging of mix is continuously done until the work is complete or work break occurs. The loading of materials is done continuously by screw feeders.
Continuous mixtures are used for very large projects such as dams, bridges, construction of high rise buildings, etc.