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
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.
In the beginning, neglect the blade action, the 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.
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 the concrete falling point is avoided.
Wet Batch Ready Mix Concrete Plants
There are various types of wet batch systems and the wet batch system is a plant-based mixer. This means that different component of concrete mixtures such as cement, aggregate, and water is mixed in the system.
Comparatively, the output of the wet batch concrete plant is greater than the 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, the 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
The half wet system includes premixing of sand, cement, and water to make a 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.