A concrete mixer (also known as a cement mixer) combines cement, aggregate (such as gravel or sand), and water to create concrete. Concrete mixers feature a round, rotating, barrel-like drum with paddles fastened to the inside of the drum. In operation, the drum tips up at an angle and a gasoline engine or electric motor rotates the drum. One end of the drum is open for loading the concrete ingredients and unloading the finished concrete. A typical concrete mixer uses a revolving drum to mix the components. As the concrete mixer’s drum rotates, the paddles lift and drop the ingredients over and over again to mix up slurry that will later harden into concrete. When the mixing is done, the drum tips down to pour out the wet mixture for use. A concrete mixer can also make mortar (but not as good as in a mortar mixer) but a mortar mixer cannot make concrete because the gravel in the mixture will jam the moving paddles.
The plaster mixer, or mortar mixers, is used to mix exterior stucco, interior plaster or mortar for brick, block, floor tile, etc., and any mixes that “do not contain rock, gravel or any other aggregates”. Many contractors use Concrete Mixers to mix mortar for brick or block, but we recommend a mortar mixer for this type of mixes.
A mortar mixer essentially is a stationary horizontal trough inside of which is a motor-driven horizontal shaft with attached paddles that perform the mixing operation. The mixing paddles can be powered by an electric motor or gasoline engine. Some mortar mixers use a circular vertical drum. In these machines, the mixing shaft, and its attached paddles, are oriented vertically.
A common misconception is that cement and concrete are the same thing. However, cement is simply an ingredient used in the creation of concrete; it is the binding element. As for mortar, it is a product composed of cement and sand. When water is mixed in with mortar, the cement is activated. Whereas concrete can stand alone, mortar is used to hold together bricks, stones, and other components.
As far as density, concrete and mortar both have a density of about 2 - 2.1 tons per cubic meter. This figure applies both to wet and cured material. However, there are special lightweight concretes as low as 1.4 t/cu. m.