M5 Oldbury Viaduct: R181 SDF repair works complete
As part of the multi-billion-pound Scheme Delivery Framework (SDF) for National Highways, VolkerLaser has completed structural repair works at South Oldbury on the R181 scheme.
The Midland links motorway viaducts, constructed in the 1970s, comprise of approximately 21km of elevated motorway in eleven sections. The Oldbury viaduct specifically carries the M5 motorway between junctions 1 and 2.
Valued at circa £4.2 million, the R181 scheme involved the repairs of bents 24/03 and 24/19A. The full scope of works included concrete repairs, gutter replacement, drainage maintenance and long-term preventative measures in the form of cathodic protection, utilising the Impressed Current Cathodic Protection (ICCP) system.
Works began with the installation of a CAT II design scaffolding on both the bents, with each scaffold footprint measuring 36.2m x 6.34m x 14m. As some areas were located above the canals, extensive encapsulation works were carried out to prevent hydro-demolition water discharging below. Due to the layout of the existing bridge, where required, our specialist team installed additional protection to specific bents in order to maintain their structural integrity throughout the critical works.
Access to bent 24/19A was made possible through close collaboration with Enfinium, who is constructing a waste-to-energy plant nearby.
During the hydro-demolition phase, 500,000 litres of water was treated in the Siltbuster units and safely discharged with consent from Severn Trent.
Once the installation of the scaffolding was in place, the team used hydro-demolition to remove the spalled and delaminated concrete from the reinforcement. A total of 241 concrete repairs were carried out across the two bents, including repairs to the crossbeam and columns. Additionally, 24 panel walls were removed and recast, and significant amounts of corroded steel was removed and replaced to strengthen the beams’ structural integrity.
To prevent future corrosion on the bents, a comprehensive ICCP system was installed. The team laid 2000 metres of ICCP cable to distribute the impressed current across the structure. To regulate the current, two transformer rectifier (TR) panels were installed, allowing the direct current to be carefully managed and alternated. Additionally, 445 square meters of CNT35 titanium mesh was applied, providing an effective conductive surface for the system. To further enhance the system's durability, 48 tonnes of dry spray concrete was used to create an overlay, protecting the mesh and other components. Finally, the system included the necessary references, with positive (anode) and negative (cathode) connections, ensuring the correct flow of current for optimal corrosion prevention. This approach ensured a well-coordinated and effective solution for safeguarding the bents from corrosion in the future.
The final phase involved the removal and repouring of the defective bearing plinths, which formed a 50 mm mastic joint around bearings, mechanically cleaning the I-beam ends and applying a new three paint system, with the guttering being replaced on both bents.
Alongside this, our team achieved an outstanding score of 41/45 in their Considerate Constructors Scheme visit. This reflects the team's commitment to respecting the community, protecting the environment, valuing their workforce and prioritising safety.
After 19 months of works, the R181 Scheme was completed in February 2025.
