Concrete is a mixture of stone aggregate, sand, cement, and water that is very commonly used in most building construction. This concrete then needs to be transported to the location where it is to be used and then placed in at the exact place where it is needed. While the batching of materials and their mixing is carried out in plants that can be located on a project site or at far off locations, the transport of concrete is carried out by using truck-mounted concrete mixers where the concrete needs to be transported over long distances.
This system of transport is most commonly used for construction projects where ready mix concrete is bought from plants often located at fair distances from work sites. The main objective in using these truck-mounted concrete mixers is to see that the homogeneity, air content, and slump of the concrete are not modified until the concrete is placed in the location where it is required. Segregation has to be prevented and workability of the concrete must be maintained.
Standard truck mixers are filled either with the dry materials that go into the making of the concrete or with ready-mixed concrete. In the case of dry mixes, the truck may also carry water tanks that allow the water to be added to the dry mix after the concrete has reached the point of discharge, and the concrete is then mixed with the water before it is discharged, using the rotating mechanisms that are mounted on the drum of the transit mixer(mixer para trasnportar).
All truck mixers are required to maintain the concrete’s liquid state through the turning of the drum until it is discharged at any construction site. These mixers have blades attached to the movable drum that facilitate the mixing. Blades can have two helixes that rotate in both directions, clockwise and counter-clockwise. These blades mix and lift the concrete while the drum rotates, and each rotation ensures that concrete is lifted and dropped back in repeated cycles. When the rotation is counter-clockwise the material gets lifted towards the end of the drum from where it can be discharged. This concrete is then discharged into chutes that guide the concrete to the location where it has to be placed. When the discharge points are far away or at higher levels, use may be made of crane lifted hoppers or concrete pumps to help in the precise placement of the concrete.
Truck mixers(camion mezclador) have either rear or front discharge drums. Rear discharge drums require careful manoeuvering of the truck to allow for careful positioning of the discharge chute. Front discharge chutes are maneuverable and allow the driver to be precise in the discharge of concrete. Truck mixers can be of various capacities and can have electronic weighing equipment that can allow accurate estimations of the amount of concrete that is being discharged. This can also allow them to load materials at any supplier and is useful where small amounts of concrete need to be transported.
Concrete truck mixers and ready mixed concrete plants have greatly reduced the need for construction sites(necesidad de sitios de construcción) with limited space to have areas set aside for stacking materials required for the production of concrete.