There are various types of ready mix concrete plants which most of them designed for specific locations or circumstances. Moreover, there are standard ready mix concrete plants but these are usually modified to accommodate for certain situations.
Concrete that are produced as per established procedures in batching plants and after that delivered to construction site by truck on which transit mixture is mounted is called ready mix concrete.
In this article, various types of ready mix plant, which are categorized based on the type of mixer, is described.
Types of Ready Mix Concrete Plants
Following are the different types of ready mix concrete plants and their mixing actions:
- Dry batch concrete plant
- Wet batch concrete plant
- Half-wet batch concrete plant
- Combination batch concrete plant
Fig.1: Ready Mix Concrete Batching Plant
Dry Batch Ready Mix Concrete Plants
This type of ready mix concrete plant produces uniform concrete mix through the mixing action of the truck mixer. The mixing action is basically a twofold mechanism. Consider the complex movement of already well mixed plastic concrete in the drum.
At the beginning, neglect the blade action, then rotation of the drum and both concrete internal friction of the concrete and its friction against drum inside surface make the concrete appears to move up the right-hand wall of the drum as shown in Figure-2.
Fig.2: Cross Section of Track Mix Action
There are two factors which affect the height that the concrete can climb up before gravity surpasses it and make it to fall. Firstly, drum surface linear velocity which based on its angular velocity and the inside diameter of the drum. Concrete falling point is increased with increasing linear velocity. Secondly, concrete workability which its decline leads to rise concrete falling point.
It is observed that, at speed of 22-27 rpm (normal speed is 10-14 rpm), the concrete spins full contact with the drum surface hence concrete falling will no longer exist. This may lead to create problems because substantially efficient local mixing will be lost if concrete falling point is avoided.
Fig.3: Dry Batch Ready Mix Concrete Plant
Wet Batch Ready Mix Concrete Plants
There are various types of wet batch systems and the wet batch system is plant based mixer. This means that different component of concrete mixture such as cement, aggregate, and water is mixed in the system.
Comparatively, the output of wet batch concrete plant is greater than dry batch concrete plant that is why it is frequently seen as large plants. Moreover, the wet batch concrete plant is necessary in the case mortar production is required.
There are different mixers sizes that range from 0.8 m2 to 6 m2 and the largest mixer drum can adequately mix about 6 m2 plastic concrete in around forty five seconds.
Furthermore, there are several factors for example, required to output, predominant type of mixes supplied, plant geometry, available space, initial and entire life expenses, upon which specific mixer is decided to be chosen.
Types of Wet Batch Mixer and its Mixing Action
Following are the available different types of wet batch mixers and its mixing action:
Rotating Drum Mixer
- Rotating drum, freefall mixing action, none tilting.
- Rotating drum, freefall mixing action, tilting.
Fixed Trough Mixers
- Fixed mixing trough within which spiral blades revolve on horizontal shafts
- Fixed mixing trough within which paddles rotate on twin horizontal shafts
- Fixed horizontal pan in which mixing paddles travel around an annular channel
- Fixed horizontal pan in which mixing paddles travel around an annular channel while revolving about their own axis
- Fixed horizontal pan in which the mixing blades traverse the entire pan floor with a planetary motion
- Fixed horizontal pan in which two sets of mixing paddles travel around an annular channel in opposite directions
- Horizontal pan rotating beneath a stationary motor unit carrying paddles, the axes of rotation being non-coincident
Reversing Drum Mixers
- System of fixed blades and shovels within a non-tilting rotating drum giving a combined freefall and compulsory mixing action.
- Fixed trough mixer with twin rotating shafts and paddles angled at about 20° arranged to produce a continuous mixing action
Half-Wet Batch Ready Mix Concrete Plants
Half wet system includes premixing of sand, cement, and water to make slurry, after that, the slurry and aggregate are added to the truck. Not only does the half-wet system decrease wear and tear on central mixer units but also substantially decline the time of batching.
Combination Batch Ready Mix Concrete Plants
Both dry batch and wet batch system is combined in this type of batching plant, and most of concrete is mixed in dry leg bur small mixers with 0.8-2 m3 is employed to deliver concrete to the customer.