During concrete production and transport, quantities of residual concrete accumulate every day, for example, when cleaning the mixing plant and truck mixers or in the case of concrete being returned from the construction site. All ingredients of the residual concrete quantities are suitable for reuse. Even the truck mixers are cleaned with recycled residual water instead of fresh water – a very environmentally friendly practice.
Sand and gravel are washed out and reused as base materials for concrete production. The left-over residual water is collected in a basin and kept in suspension by an agitator. A proportion of the residual water is fed back into concrete production.
Recycling plant LRT 622 – trough system in operation
The trough design of the LRT 622 plant can hold an exceptionally high volume of washing water, thus permitting larger quantities of material to be fed at short intervals. The large washing trough is closed and consists of two half shells which can be easily opened for maintenance procedures. A two-stage conical washing spiral operates inside the trough and is driven by a tried-and-tested, robust flat gear motor. All bearing points are located outside the wet area, which gives them an extended service life. The loading hopper is positioned at the side of the washing trough but can alternatively also be mounted at the front. The plant is almost fully galvanized to ensure a long service life. The two washing gantries on the loading hopper permit simultaneous cleaning of two truck mixers. The plant has a washing capacity of max. 20 m³ per hour. For brief periods (batch loading with an empty trough), the plant can even be fed with 2 m³ of material within five minutes. The plant is complemented by a galvanized raised tank with agitator in mobile design and with a holding capacity of 40 m³.
A PLC enables all processes to be performed in a fully automated operation. In addition, the control system can be adjusted to the customer’s individual requirements. The plant is fitted with a heating system and is therefore suitable for operation in winter.
Zero-emission and quiet transport of concrete
In addition, Liebherr and Designwerk have developed the first fully-electric truck mixers with drum capacities of 10 m³ and 12 m³ respectively, mounted on a 5-axle chassis. The first units will be operated by Swiss customers Holcim and Kibag. This concept is perfect for Switzerland, where vehicles with a gross vehicle weight of 40 t are permitted to drive on 5 axles. Concrete production at the concrete plants is clean and environmentally friendly, since the mixing plants are operated using electrical energy. This does not yet apply to the transport of concrete to the construction site: powerful diesel engines have to date been used for this purpose – associated with emissions in terms of both exhaust gases and noise.
The new ETM 1005 and ETM 1205 truck mixer models mounted on a Futuricum chassis will change that: they can be relied on to transport large quantities of concrete to the construction site quietly and without producing exhaust emissions. Since distances from the concrete plant to the construction site are relatively short compared to freight transport, the fully-electric solution is particularly well suited to this purpose. In addition, the vehicles always return to the concrete plant, which provides the battery charging infrastructure. High storage capacities usually only require recharging of the batteries overnight. Featuring an equivalent of 680 PS, the Futuricum chassis is extremely powerful and ideal for handling the weight of the concrete. The energy recovered when braking or driving downhill increases the truck’s range further while reducing operating and maintenance costs. The drum drive system developed by Liebherr and ZF consists of an efficient and low-maintenance unit comprising an electric motor and mixer gearbox. The truck mixer superstructure from Liebherr features a low dead weight paired with optimized transport volume, an extended service life due to the use of special wear-resistant steel, and ergonomically designed controls and access steps. A dual platform system left and right permits flexible the positioning and attachment of accessories or ancillary equipment in accordance with customer requirements.
Perfect overall concept
All component groups, the chassis and the mixer superstructure have been perfectly matched to one another by Liebherr and Futuricum. Weight distribution to the axles is ideal to ensure excellent driving performance. A temperature management system provides the necessary cooling or heating of the components.
In addition to the ready-mixed concrete sector, the new fully-electric truck mixer is also intended for use at the precast concrete plant in cases where there are no plans to install a bucket conveyor system but to nevertheless ensure quiet and emission-free concrete transport inside the production building.