Aquaforce Concrete Services has carried out floor cutting and hydro demolition works on the Thames Bray Bridge Widening Project for the M4 Smart Motorway development, on behalf of the Balfour Beatty Vinci JV for Highways England.
The Smart Motorway project will see 11 bridges over the M4 between junctions 3 and 12 replaced or upgraded to ensure they have capacity to accept the new four lane carriageways.
The complex Thames Bray bridge widening works require the ‘stitching’ of three additional longitudinal deck beams to the existing deck. The new bridge beams, each weighing nearly 400 tonnes were installed on the North side of the existing bridge and tied to the existing sub-structure by structural bracing, extending the width of the bridge deck by eight metres and enabling the addition of four traffic lanes.
To facilitate the works, Aquaforce Concrete Services was engaged to carry out the removal of 1900mm of the existing northern cantilever concrete deck slab.
To ensure maximum efficiency within the already tight programme, Aquaforce removed the outer 1300mm of the slab using floor sawing techniques, cutting the slab into 2000kg, 2000mm x 1300mm sections, lifting them out a section at a time. Fifty one sections were removed in total.
The remaining 600mm of the concrete slab was then removed using high pressure water jetting (hydrodemolition) to ensure the final 600mm of existing rebar was left in place, undamaged and ready for connection to the reinforcement in the new deck.
As the Thames Bray Bridge carries the M4 Motorway over the River Thames at Bray, it was critical that no waste water from the process entered the water course below. A bespoke encapsulation system was developed by BBVJV and Aquaforce and installed by BBVJV to ensure protection of the water course.
The concrete removal works were carried out, on budget, on programme and to the satisfaction of the Client and the Environment Agency.
The upgraded M4 smart motorway is expected to be open to traffic by spring 2022.
BBV JV has released the follow video of the works so far.