Automated Concrete Placement
With AUTOCOR (Automatic Concrete Placing On Rail) Putzmeister AG has developed a trend-setting system for the automated delivery and placement of concrete in precasting plants. The AUTOCOR installation makes particularly sense in plants that process pumpable and preferably self-compacting concrete for medium and large-sized precast elements. If an expansion is planned for older plants, the AUTOCOR system can be easily retrofitted.
Putzmeister uses tried and tested components and controls for the AUTOCOR system. For example, the rotor pump system that is well known from the PUMI®, flexible placing booms with a horizontal reach of 16 m to 28 m and a mixer drum with a capacity of 7 m3 as temporary storage. The complete unit is mounted on a rail-guided working platform and needs no support devices. There is also a control unit which is integrated into the production process and the EBC system which has proven its worth for many years on PM truck-mounted concrete pumps. Among other things it damps the movement of the concrete placing boom while shifting and rotating even by high output. Beside this, the EBC system can - if required - limit the working radius of the placing boom, so that it does not collide with any floor beams or other obstacles in the area.
A typical example of rational, automated concrete placement in precasting plants is the production of tower segments for wind power systems. Due to the varying diameter the tower segments consist either of half-shells or of differently dimensioned one-piece ring elements. These parts are manufactured from pumpable standard concrete and from self-compacting concrete (SCC). To avoid the penetration of air during the processing of the SCC material, when filling the differently sized formwork units you must ensure that the concrete level is built up from the bottom, i.e. that the end hose is immersed deeply into the unset filled concrete. This is ensured at all times by the automated concrete placement performed by the AUTOCOR system, because in connection with the EBC control unit and additional sensors the placing boom is raised automatically.
A monorail overhead bucket transport system provides the AUTOCOR with concrete from the mixing plant. The material is treated once again and homogenized with the previous batch in the AUTOCOR mixer drum. In addition the drum serves as a temporary storage facility and ensures that the AUTOCOR can operate continuously. The concrete is delivered by a rotor pump which Putzmeister offers in two versions for use in precasting plants. An optional flow rate of 60 or 80 m3/h (max. theoretical) is available. Due to the design hardly any residual concrete arises with this pump system. The workshop remains clean because the concrete is transported within a closed system (overhead bucket transport system - mixer drum - pump - boom delivery line - formwork). When the machine is moved a pneumatically actuated squeeze valve attached to the end hose ensures that there is no concrete after-dripping during relocation.
Operating experience with AUTOCOR is nothing but positive. According to customer information production can be increased by up to 60% compared with the previous method using automated concrete placement for precast elements. Due to the intensive treatment in the AUTOCOR mixer drum a consistently high quality of unset concrete is also obtained. Any later labour-intensive reworking of the precastings, like smoothing and grinding, is reduced to a minimum. A change in the concrete type is also possible without difficulty.
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