8.1 : コンクリートの混合

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.