With both lanes of the A631 in need of repair and resurfacing, Metrail carried out bridge deck waterproofing and associated concrete repairs on the A631 southbound carriageway of the Tinsley Viaduct in two five-week phases, on a total of 18,000 sqm of deck and 1850 sqm of walkway.
The challenge
The contract awarded to Metrail covered the following scope of work: removal of the existing waterproofing as well as removal of the existing walkway surfacing; scraping of the main deck in order to remove any remaining surfacing and waterproofing; the identification and carrying out of concrete repairs prior to waterproofing; the application of waterproofing, including a bond coat; and the application of combined waterproofing/high friction surfacing on the walkway.
Facts & Figures
When?
Two five-week phases commencing in May 2019
Where?
A631 southbound carriageway of the Tinsley Viaduct
What?
Bridge deck waterproofing and associated concrete repairs
Structure
Tinsley viaduct – a two-tier steel box girder viaduct
Solution approach
In order to complete the works, a traffic management scheme needed to be put in place which enabled two-way traffic on the northbound carriageway, thus allowing full closure of the southbound carriageway, enabling us extended daytime working for completion of the resurfacing. The Metrail scope commenced once the asphalt surface on the main carriageway had been removed down to approximately 10–20mm.
Technology
Eliminator, the GPC Advanced Technologies waterproofing system, is a rapid cure, cold liquid spray applied system, which is based on methacrylate monomers which forms a tough, flexible seamless membrane with no vulnerable joints. It’s resistant to chemical attack by oil, fuels, brine and dilute mineral acids. Where asphalt is to be laid a bond coat — also known as a tack coat — is applied as well. When it comes to the walkway, we employed Safetrack, a GCP product specifically designed to provide a durable anti-skid surface.
Execution
Employing a large Caterpillar tracked scraper with a bladed head, the first thing we did was remove as much of the remaining surface as possible before fine milling to remove any remaining traces of the old surface. We then carried out an extensive number of concrete repairs using Metaset Rapid Repair Mortar which cures to full strength in 1–2 hours.
Next up: sand blasting the surface and carrying out adhesion testing. We then primed the surface and manually sprayed it with the Eliminator system.
Rather than screeding the steel walkway — a method that had proved time consuming and costly — we proposed using Safetrack. After stripping and cleaning the old walkway surface down to the bare steel, we then primed and waterproofed it with Eliminator so that Safetrack could be applied.
Next up: sand blasting the surface and carrying out adhesion testing. We then primed the surface and manually sprayed it with the Eliminator system.
Rather than screeding the steel walkway — a method that had proved time consuming and costly — we proposed using Safetrack. After stripping and cleaning the old walkway surface down to the bare steel, we then primed and waterproofed it with Eliminator so that Safetrack could be applied.
Results
This project offered us the opportunity to showcase our extensive experience and skills in waterproofing and concrete repair, and we’re pleased to report that Metrail achieved all the timescale milestones to ensure an on-time opening of the A631 southbound carriageway of the Tinsley Viaduct. Sound project management, technical competence and close coordination with all stakeholders involved were key to the success of the project.
Impressions from the Tinsley Viaduct Concrete Repair & Waterproofing
