Forced-action mixers, the most effective way to mix on the construction site

Forced-action mixers consist of a stationary or rotating mixing bucket and one or more rotating mixing arms. These tools accelerate and force the material into a uniform mixture by shearing, kneading and circulating – hence the name "forced-action mixer". This mixing principle actively moves the material and enables the individual components to mix completely and evenly in a short time. This ensures homogeneous mixing and consistent quality over the long term. It is important that the combined rotation and circulation movement of the mixing arms and an additional edge scraper ensure that no unmixed material remains at the edge of the bucket and on the floor. In addition to the classic application area of concrete production, the mixing principle is particularly suitable for sensitive and highly polymer-modified materials to ensure complete homogenisation.

Forced-action mixers are available in a wide range of sizes and designs, from small laboratory appliances to large industrial machines. They can be controlled manually or automatically depending on requirements and are used in many industries where a precise mixing ratio of materials is required. These mixers can be mobile (for the construction site) or stationary (in production processes). They are usually available for mixing quantities starting at approx. 40 litres up to several thousand litres. 

A typical area of application for forced-action mixers includes the production of ready-mix concrete in concrete plants, where a precise formula of cement, sand, gravel, water and additives is required to ensure high strength and durability of the end product. In addition, forced-action mixers are absolutely essential when it comes to the precise mixing of multi-component, plastic-modified products such as industrial floor coatings or epoxy resin mortar.

The principles illustrated merely show the diversity of the designs. The features of the machines available on the market vary considerably in some cases. This applies to the design and shape of the mixing bucket, the drive principle, the mixing elements used and their speed, as well as the feeding and removal of material. These factors depend on the intended application and the range of materials to be processed. The mixtures can be made as dry or wet mixes. On construction sites, these are usually wet mixes.

The most common designs on the market are:

• Pan or ring-pan mixers, sometimes also called trough mixers; several mixing arms are driven by a central shaft and guided through the mixing zone or driven centrally by a gearbox and moved in a circular motion (planetary).
• Twin-shaft mixers or horizontal mixers with one or two horizontally arranged mixing shafts with paddles

Another feature that characterises the mixers is the way in which they deliver the mixtures:

• Batch or discontinuous mixing: mixes a defined quantity per process
• Continuous mixing: Material is continuously fed and mixed

1.      Active mixing tools
The mixing bucket contains rotating arms or paddles that fully grip the material, knead it intensively and break it down. In some cases, mixing elements are driven at different speeds.

2.      Highly homogeneous mixing
Ideal for materials with a high density or viscous consistency, e.g. thick mortar, swelling mortar, plastic-modified mortar or special mixtures. The decisive factor here is the even distribution of the solids in the material, as well as the simultaneous, intensive dispersion of the fine components for a high mixing quality.

3.      Consistent mixing quality
The constant rotation of the mixing tools means that the quality of the mix is consistently high – important for materials that are sensitive in terms of building physics. At the same time, the peripheral speed of the mixing tools is a decisive factor, depending on the viscosity and properties of the material to be mixed. 

4.      Suitable for small to medium quantities, on construction sites
Particularly popular on interior construction or renovation sites where precise mixtures are required in limited quantities.

5.      Fast mixing times
Due to the highly efficient mixing effect, the mixing cycles are usually completed in just a few minutes, which speeds up the application of the material quantity and thus the construction progress.

6.      Reliable material feed
Many models have a grid attachment or a filler opening, as well as additional safety features to prevent injuries.