Enormous pressure on the tie rods

Heating plant in Switzerland with 14-meter-high architectural-concrete walls made of self-compacting concrete

Data & Facts

  • Project
    • Heating plant in Kaiseraugst (CH)
  • Principal
    • AEW Energie AG, Aarau (CH)
  • Contractor
    • Ernst Frey AG, Violenried (CH)
  • MEVA systems
  • Engineering and support
    • MEVA Schalungs-Systeme AG, Seon (CH)

Rapid pouring in 4-metre steps

Enormous pressure on the tie rods
Heating plant in Switzerland with 14-meter-high architectural-concrete walls made of self-compacting concrete

Just outside Basel, Ernst Frey AG has built a heating plant with walls up to a height of 14 metres made of self-compacting concrete. This required extremely robust formwork with hard-wearing facings, safe working platforms and stable bracing.

A wood-fired heating plant for the Swiss municipality Kaiseraugst was taken into service on schedule in the autumn of 2020. The plant commissioned by the Aargau energy supplier AEW Energie AG uses wood chips from the region’s forests as well as waste wood from the surrounding area in order to supply up to 1,700 households reliably with cozy warmth.

Limited space on the construction site
The shell of the single-story industrial building with a pent roof is 69 metres long, 15.4 to 18.6 metres wide and 12.2 to 14.1 metres high. Due to lack of space, the building was completely constructed in the steep slope of a former gravel pit, which was excavated and extensively secured for this purpose. The minimum clearance was at times just one metre – hence providing little room to pour concrete. The general lack of space on the construction site required a well-thought-out logistics concept. Furthermore, the principal wished for a high architectural-concrete quality.

The construction company exploited the advantages of self-compacting concrete. This material is ideally suited for the erection of high walls and achieves the specified concrete quality effortlessly due to the inherent high quality of its surface finish. Self-compacting concrete has a higher compressive strength than ordinary concrete and good flow properties. This enables demanding formwork geometries and other component sizes to be formed in less time. However, the use of self-compacting concrete also places greater demands on the know-how and ability of the formwork specialists as well as on the formwork itself: Due to the higher prevailing fresh-concrete pressure, the formwork used must be robuster and the facings must have better sealing properties.

The team from Ernst Frey AG led by construction manager Christian Müller employed MEVA’s Mammut 350 to form the large-format walls. The high-performance industrial formwork fulfilled the requirements on the construction site in Kaiseraugst with a permissible fresh-concrete pressure capacity over the entire surface of 100 kN/m² and the durable alkus all-plastic facing. The facing does not absorb water, does not swell or shrink, and its smooth, robust surface guarantees a high-quality concrete finish, even after repeated use.

Mammut 350 panels with a total surface area of 500 m² were used on the construction site near the Rhine and were supported by 28 Triplex heavy-duty props. A total length of 100 metres of the modular safety system SecuritBasic was installed. Mammut 350’s impressive forming areas (up to 8.75 m² per panel) and the system’s simple handling in conjunction with the Triplex props enabled the construction work to progress rapidly despite having to adhere to the stringent Swiss safety standards. It goes without saying that SecuritBasic fulfils the high statutory requirements such as the accident prevention regulations issued by Suva, the Swiss national accident insurance fund.

Rapid pouring in 4-metre steps
Pouring took place from the full height and the dimensions varied due to the inclined roof. 250 x 300 cm Mammut 350 panels were comfortably connected on the ground for a basic height of 9 metres, the SecuritBasic platforms were attached, and the unit was then erected using a crane. Height extensions from 4 to 5 metres, also as fixed units with SecuritBasic platforms, were then placed on top. After pouring, the workers simply relocated the complete unit.

The fresh-concrete pressure of 100 kN/m2 was constantly monitored by the concrete-pressure sensors installed.  This enabled 4-metre-high sections to be poured, followed by a 40-minute break before the next section was poured. The team from Ernst Frey achieved the high architectural-concrete quality specified without problem using the durable, robust, lightweight and simple-to-clean alkus all-plastic facings.