The concrete mixer is a machine that mixes cement, sand and gravel aggregates and water and mixes them into concrete mixtures. It is mainly composed of mixing drum, feeding and unloading mechanism, water supply system, prime mover, transmission mechanism, frame and supporting device. According to the nature of work, it is divided into batch type (batch type) and continuous type; according to the principle of mixing, it is divided into self-falling type and forced type; according to the installation method, it is divided into fixed type and mobile type; according to the discharging method, it is divided into tilting type and non-tilting type; According to the structure of the mixing drum, it is divided into pear type, drum type, double cone, disc vertical shaft type and circular groove horizontal shaft type.
The self-falling mixer has a long history. As early as the early 20th century, drum-type concrete mixers driven by steam engines began to appear. After the 1950s, double-cone mixers with reversal discharge type and tilting discharge type, and split drum mixer were successively introduced and developed. There are radially arranged mixing blades on the inner wall of the mixing drum of the self-falling concrete mixer. When working, the mixing drum revolves around its horizontal axis, and the materials added to the mixing drum are lifted to a certain height by the blades, and then fall under its own weight, so that the repeated movement can achieve the effect of uniform mixing. The structure of the self-falling concrete mixer is simple, generally mixing plastic concrete. Since the emergence of the forced mixer in the early 1950s, it has been rapidly developed and promoted. The first to appear was the disc vertical shaft forced concrete mixer. This type of mixer is divided into two types: turboprop type and planetary type.
After the 1870s, with the application of lightweight aggregates, circular trough horizontal-shaft forced mixers appeared. They are divided into single-shaft and double-horizontal-shaft types, which have the characteristics of both self-falling and forced mixing. . The linear speed of the mixing blade is small, the wear resistance is good, the energy consumption is low, and the development is fast. The rotating shaft arm frame in the mixing drum of the forced concrete mixer is equipped with mixing blades, and the materials in the mixing drum are added to form a cross flow under the strong stirring of the mixing blades. This mixing method is far stronger than the self-falling mixing method, and is mainly suitable for mixing dry hard concrete.
The continuous concrete mixer is equipped with spiral mixing blades. Various materials are continuously weighed according to the mixing ratio and then sent into the mixer. The mixed concrete is continuously discharged from the discharge end. This kind of mixer has short mixing time, high productivity, and its development is eye-catching. With the development of concrete materials and construction technology, many concrete mixers with new structures have appeared one after another, such as steam heating mixers, supercritical speed mixers, sonic mixers, swing disc mixers without mixing blades, and concrete mixers with secondary mixing.