Leca® Lightweight Concrete creates an engineering solution for the preservation of biodiversity
[GERMANY] Since the year 2000, the bypass of the city of Celle has been developing and incorporates various geotechnical structures - primarily bridges of different functions, to bypass consistent and busy traffic.
In the planning area of the bypass development, various bat species have settled over the years, which need to be protected through habitat improvement measures. Additionally, typical nature conservation measures such as planting and reforestation along the B3, two bat bridges are being developed as part of the planning for the bypass. These structures are not exposed to large dynamic loads and essentially only have to bear its own weight and have been designed to allow the various bat species to cross safely. The bridge body is divided lengthwise by three beams into two flight lanes, where further elevation is to take place. The interspaces will be filled with soil and planted afterwards. In order to reduce the total weight of the bridge, the reinforced beams (approx. 190 m3) were made of lightweight concrete LC 12/13 with an apparent density of < 1.200 kg/m3, which reduces the total weight of the bridge by 240 tonnes.
WHAT WERE THE CHALLENGES FOR LIGHTWEIGHT CONCRETE?
The design concept was characterised by different challenges:
• LC 12/13 D 1.2 to be produced with a lightweight aggregate granulation for processing
• Transport and installation with changing consistencies
• Transportation to the construction site by means of a truck-mounted and site crane in concrete bombs
• Mixing time in the factory, logistical time, keeping delivery rates within the time slot of 10 h
• 2 concrete layers (130 m3 + 60 m3)
INSTALLATION OF THE LIGHTWEIGHT CONCRETE
The lightweight concrete was mixed by HEIDE-TRANSPORTBETON GmbH, based in Celle, and was then transported and placed in concrete bombs to the corresponding construction section using a truck-mounted and site crane.
RECIPE OF THE LIGHTWEIGHT CONCRETE
The components for the lightweight concrete was developed incorporating Fibo ExClay Deutschland GmbH and the concrete laboratory of HEIDE- TRANSPORTBETON GmbH.
WHAT ARE BAT BRIDGES?
Bat bridges are structures erected over highly frequented traffic routes to allow low-flying bats to cross trunk roads and railway lines without danger.