Concrete mixing ensures a homogenous blend where aggregates are well-coated with cement paste. Concrete mixing is typically done using two main types of mixers: batch and continuous. Batch mixers handle one batch at a time, thoroughly combining materials before discharging and receiving the next batch. In contrast, continuous mixers receive a steady flow of ingredients, mixing them consistently and discharging without interruption. Within batch mixers, tilting drum mixers mix with internal blades and discharge by tilting, while non-tilting drum mixers use a chute or reverse rotation for emptying. Pan-type mixers, with paddles rotating about a vertical axis, and dual drum mixers, allowing sequential mixing in two drums, are also common in batch operations. Concrete mixers are available in a wide range of capacities ranging from 1.5 cubic feet to 17 cubic yards. Mixing a volume that is only a minor portion of the mixer's total capacity is inefficient and can lead to inconsistent mixes. Similarly, overloading the mixer beyond its recommended capacity by more than 10% can also result in a non-uniform mix. To verify the mixer's efficiency in yielding uniform mix across the batches, sampling is conducted at various discharge points and evaluated for consistency according to set criteria such as density, air content, slump, and compressive strength.
The primary goal of mixing concrete is to stir its ingredients, ensuring the aggregates are evenly coated with cement paste, resulting in a uniform mixture.
Typically, concrete is mixed using batch mixers or continuous mixers.
Batch mixers process one complete batch at a time, mixing the ingredients and then discharging them before the next batch is introduced. There are four types of batch mixers: tilting drum mixers, non-tilting drum mixers, pan-type mixers, and dual drum mixers.
A tilting drum mixer uses internal blades to mix concrete, discharging the mixture by tilting the drum. Contrarily, a non-tilting drum mixer discharges the mix through a chute or by reversing the drum's rotation.
Mixing concrete in batches can be done in a pan-type mixer using paddles or in a dual drum mixer involving a two-stage mixing process within a tandem setup of drums.
Continuous mixers automatically and continuously receive ingredients, which are then uniformly combined using a drum-type mixer or a screw moving inside a stationary housing, resulting in a constant outflow of mixed concrete.
Lastly, to ensure the mixer's efficiency in yielding a uniform mix, samples at specific discharge points are collected and evaluated for consistency.
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