From over 3000 concrete recipes, customers of Rennig Beton GmbH & Co. KG – from the non-reinforced variant to highly corrosive types for filling stations and road surfaces. To mark the company’s anniversary, the family-run business commissioned a third plant in the Augsburg area – and once again, the choice fell on an Ammann mixing plant.

The family business Rennig Beton GmbH & Co. KG supplies Augsburg and the surrounding area with fresh concrete and gravel. The company, which started out as a haulage business in 1919, celebrated its centenary by opening a third plant. The Gersthofen site is very conveniently located at the Augsburg-West motorway junction and supplies the Augsburg district and surrounding area with standard and special concrete.

The site also offers sufficient space for a building ensemble that focuses on efficiency and environmental protection: mixing plant, a large intermediate material store, a computer-controlled residual concrete recycling plant connected to a ready-mixed concrete plant and a truck mixer washing plant with integrated waste water recycling.

The differences in height on the 10,000 m² large plant site had prompted the two technical plant managers to choose a linear mixing plant, in which the linear bins are fed directly from trucks. Dipl.-Ing. Josef Rennig and Dipl.-Ing. Michael Linke opted for a mixing plant from Ammann, a CBS 120 SL Elba. Compared to a tower plant, this type offers a higher storage capacity. This is an enormous advantage for the company, which stores a wide variety of binding agents and aggregates.

The skip version delivers up to 121 m³ of standard concrete per hour in continuous operation. The modular design enables operators to implement various special features, thus expanding their range to almost 3,000 concrete recipes. In particular, the addition of aggregates is precisely matched to the requirements of the operation: Steel and synthetic fibers are fed from a separate hopper via a special feeding device placed directly above the weighing belt which is over 30 meters long.

In Gersthofen, a total of six cement silos are available, each has a capacity of 100 tones, all with a TRF filter system and a rope probe overfill protection system. Aggregates are fed directly onto the weighing belt, which delivers the desired quantities to the skip. This discharges directly into the mixer via the mixer inlet flap. Pre-tempering ensures a high output quality in the cold season. For this reason, a heating system heats the aggregates with hot air, the mixing water is also pre-tempered accordingly. Generously dimensioned EZL 80/100 cement screws conveyors guarantee the required dosing capacity and continuous operation of the plant.

The plant is equipped with a CEM 2660 S Elba single-shaft mixer.

Its technology and unique mixing system is being used for the first time in Rennig’s plants. With a batch size of 2.66 m³, it achieves maximum performance for special concretes. Equipped with Elba Wear Protection (EWP), the mixer shows an extra longevity and requires little maintenance. Combined with the integrated mixer cleaning system, cleaning work is reduced to a minimum. Internal shaft seals and external shaft bearings prevent concrete fluid from damaging them and guarantee a long service life.

The plant is controlled by a customer supplied PTB-approved PLC certified control system which is also used by Rennig in other plants. Rennig uses this model because it was specially developed for rational concrete production and, if necessary, to controls several scales. But nothing replaces the expert’s view: the finished concrete is also visually checked trough mixer camera, so that only the usual high-quality product leaves Otto-Hahn-Strasse 5, 86368 Gersthofen.

The Rennig team can now use the Ammann CBS 120 Elba to produce their own special developments, such as RSC (RennigSteelConcrete) or RAC (RennigAirConcrete), at an optimum speed and quality. This means that the company, which has a workforce of over 50, is well equipped for the future and can look forward to the next 100 years with confidence.