Tons of concrete: Spesa remediates Innerstetal bridge in record time

Hildesheim, Germany – On December 6, 2021, in just one day, SPESA Spezialbau und Sanierung GmbH completed concreting work for superstructures of the second construction section of the Innerstetal bridge, on the A7 highway in the direction of Hanover near Holle. To accomplish this, 23 concrete mixers and four enormous concrete pumps ran at full speed without interruption. Working tirelessly in two shifts, 70 workers moved approximately 100 m³ of concrete per hour over a distance of 150 m – a real feat of strength.

The necessary concreting work started in the central span of the bridge, from the load-bearing elements of the structure up to the outer base of the roadway slab. After that, the team used the concrete pumps to work from the abutments toward the central span. This step also included construction of the final crossbeams, which will later accommodate the roadway expansion joints and support the roadway slab. Upon completion of the load-bearing elements of the bridge, concreting work for the roadways was carried out. Vibrators were used to seal the inserted concrete. Once the surface of the roadway slabs was sufficiently hardened it was smoothed, in some places by machine and in others manually. “In total, 300 loads were required for 2,625 m³ of concrete,” explains Herbert Gerrads, Authorized Representative of SPESA Spezialbau und Sanierung GmbH, who was on site on December 6. In August 2020, a similar quantity was already brought in for the roadway in the direction of Kassel. As a result, approximately 5,000 m³ of concrete was installed for the two construction sections within a short period of time. “This alone makes the site unique and tops any project I have supervised before during my 24-year career in bridge construction,” emphasizes Site Manager Björn Gorsboth from SPESA Spezialbau und Sanierung GmbH. “The scale of this project meant that coordination was far from easy. We needed to ensure that all equipment, materials and people arrived at the right place at the right time without any idle time.”

The site environment was also challenging: Because the bridge spans a nature reserve, the area available for site installation was restricted. This meant that limited space was available for the extensive work and interim storage of required materials. In particular the demolition and support frame for the central section of the bridge, with a span of 50 m, and the actual demolition of the old bridge structure in early 2020 required extreme caution and precision.

But these challenges were not a problem for Björn Gorsboth and his team. On the contrary: “Our work is proceeding well. Thanks to perfect planning, smooth progress and exemplary teamwork, we expect to actually shorten the construction time by three months,” he proudly reports. In the next work step, bracing work is now being carried out on the bridge. This will give the concrete additional stability and secure it in its final position. In addition, the superstructure will be stripped and the area next to the guardrail will be cased and concreted. After 35 months, the work executed by Spesa is anticipated to conclude in May 2022, allowing the Innerstetal bridge to reopen for traffic in December 2022.

Upon completion, only one refurbished bridge will remain for the public. But this is a truly special structure for everyone who has been involved in the project. “Each individual section has its own story and memories for me and many others,” concludes Björn Gorsboth.