Paddle mixers are machines which ensure homogeneity of the mixture of concrete components. They are found on concrete mixing plants but also on sites and are used particularly in the preparation of special concretes.
They come in different shapes according to the model, however, they are all designed with the same mechanism; blades fixed onto one or more shafts inside a tank called a "trough" turn the mixture by their movement. This is a critical step on a site, since it influences the quality of the material.
However, in the last twenty years or so, technology has evolved considerably. In fact, concrete is no longer simply a mixture of four basic materials. The use of liquid admixtures (super-plasticizers, viscosity agents etc) and different additives (silica fumes, pulverized fuel ash etc) is now widespread. In addition, high-performance concretes (BHP) and self-levelling concretes (BAP require longer mixing times than traditional concretes.
Thus, one finds "planetary mixers", where the mixing blades are fixed onto two vertical rotation shafts hooked to a "planetary rotating blade". Manufacturers have also perfected a vortex mixer, with blades resembling the forked feet of an insect. Furthermore, some models have built-in horizontal shafts, onto which the blades are fixed.
Owing to the ever-increasing variety in this field, the capacity of the machines is very different; from 500 to 6000 litres, according to site requirements.