Jet-grouted underpinning with sustainable cement for the Friedrich Ebert School in Wiesbaden

As a technology leader in specialist civil engineering, PORR is mindful of its responsibility towards the environment. The Düsseldorf branch demonstrated this with the construction pit underpinning it produced for the Friedrich Ebert School in Wiesbaden. The foundation was built with 379m³ of jet-grouted bodies using low-CO₂ cement in order to be as environmentally friendly as possible. The CO₂ savings are huge.

Different foundation heights necessitated securing the neighbouring building

The Friedrich Ebert School on Wiesbaden’s Balthasar Neumann Strasse describes itself as a centre of excellence for training and development in technical and service professions. Since renovating the old building, which was built in the 1970s, would have been too expensive, it is being replaced by an energy-efficient, multi-storey new building with open, transparent, and flexible learning environments. The school’s state-of-the-art main building adjoins the north side of the workshop building, newly opened in 2015. It has deeper foundations, so the existing foundations had to be underpinned before the construction pit could be built. The Düsseldorf branch produced 370m³ of jet-grouted bodies including anchoring for this purpose. In addition to cost and schedule reliability, the team scored highly with its resource-efficient, high-quality realisation.

Sustainable cements reduce CO₂ emissions by up to 39%

Around 570t of CO₂-efficient Portland composite cement CEM II/C-M (S-LL) 42.5 N-NA from Dyckerhoff was used for the cement slurry. Like all large manufacturers, Dyckerhoff, which was founded in Wiesbaden, is working to reduce the fuel and production-related CO₂ emissions of its concretes and cements. Approximately two-thirds of the raw material-related CO₂ emissions generated during conventional cement production are caused by the deacidification of the main constituent: limestone. The production of sustainable CEDUR cements involves replacing up to 35% of the class CEM I Portland cement clinker with calcium-containing, alternative raw materials that have already been deacidified, such as granulated blast furnace slags and limestone flours. This reduces CO₂ emissions by up to 39% compared to conventional cements. The cement plant was only 6km away from the construction site, so the advantageous location was also fully reflected in the carbon balance. “We were able to process the carbon-reduced cement perfectly, and the compressive strength was even higher than required”, confirms branch manager Andre Schürmann. The results of the compressive strength tests performed according to DIN EN 12390-3 were 6.2N/mm² to 6.8N/mm². This clearly exceeded the minimum requirements of 3.5N/mm².