A602 Dane End

S. Evans & Sons’ team completed the complex deconstruction of an existing concrete bridge deck on the new A602 link road near Stevenage, ready for the installation of a new bridge.

Calling on the expertise of a specialist hydro-demolition contractor, the team managed the removal of 400mm of concrete from the structure’s abutments using high-pressure robotic water jets. This exposed the existing rebar starter bars, for recoupling during installation works.

Different concrete cutting techniques were used to separate the bridge from the existing abutments and enable the deconstruction and hydro demolition. Floor saw separation cuts were made to the deck slab to release each UB, while wire saw cuts were made to the diaphragm to ensure that each section of the bridge could be lifted precisely between the confines of the supporting structure and other site constraints.

Each section of the deck was removed using a 1000te mobile crane and the lift weights ranged from 125te to 98te. Lifting activities were planned and managed by our in-house lifting team. Due to the size of the deconstructed bridge deck and location of the project, all sections were mechanically processed within a laydown area before being segregated and recycled. All demolition waste was recycled locally.

To ensure full environmental compliance, 6,000 tonnes of water used in the saw cutting and hydro-demolition process were collected in a specially created catchment pond. This prevented concrete slurry run-off entering the local watercourse. The slurry was treated and removed from site.

The team worked with precision in confined spaces throughout the project to protect the integrity of the abutments, which were re-used for the new bridge.

This complex partial demolition was completed as part of an exacting nine-week programme.