Panorama bar at the LGS Neustadt an der Weinstraße – Practicality of calcined clays in focus
For the 2027 State Garden Show (LGS) in Neustadt a. d. Weinstraße, a building will be erected, using a CEM II/C-M (Q-LL) as binder containing 30 % calcined clay in combination with 15 % limestone powder and just 55 % clinker (incl. sulphate carrier), for the first time in Germany. The panorama bar on the Neustadt viewpoint is a single-story building in reinforced concrete construction with a walkable roof, that is accessible via a ramp as well as a staircase. All concrete elements will be made in fair-faced concrete design using cast-in-situ concrete.
The concrete used for the panorama bar construction project complies with the requirements of C30/37 XC4 XF1 WF and was subject to a case-by-case approval. It was important to the building contractor to use regional raw materials and to substantially reduce the GWP of the concrete by 35 %. The production of the calcined clay including grinding could be realized in cooperation with the Goerg & Schneider company. For this purpose, a locally available clay from the Westerwald region with a content of 28 wt.% kaolinite and 33 wt.% phyllosilicates 2:1 and 37 % quartz was selected and calcined in a tunnel kiln. In cooperation with TBS GmbH and Ha-Be Betonchemie GmbH, several laboratory and factory trials were conducted to design a concrete that complies with the required hardened concrete properties as well as the corresponding specifications concerning the consistency behavior (F4 consistency over 60 min) and is applicable in practice. To achieve this, superplasticizer concepts were developed and pumping tests carried out.
The early strength of the concrete was 20 MPa after two days and reached 50 MPa after 28 days. The durability characteristics of freeze-thaw resistance (CIF), carbonation and water impermeability have been successfully verified in the laboratory.
The selection of the constituents for the binder and the scientific monitoring of the transfer into practice were carried out as part of the trilateral research project (DFG-FhG) supported by DFG and Fraunhofer under project number 519196620.
