Our use of concrete repairs and cathodic protection instead of the demolition and replacement of the A19 viaduct will prolong its life by 75 years and eliminates the need for over four thousand tonnes of concrete waste – the equivalent weight of 101 Boeing 737s.
Since opening to traffic in 1975, the 1.9km structure has had problems with corrosion due to water entering the structure through joints in the bridge deck. This has made the viaduct prone to early deterioration so repairs including demolition and replacement of the piers had already been necessary.
Our client, Autolink and the asset owner, National Highways agreed that further demolition and replacement of the piers was not an optimum solution when considering health and safety, sustainability and the disruption this would bring. Instead, they wanted to appoint a team who would use new techniques and technology to repair, rather than replace the piers.
Modern technologies and techniques
The appointed team, including AECOM as the scheme designer, used impressed current cathodic protection (ICCP) to add residual life to the structure and eliminate the possible need to demolish and replace it in the future.
ICCP is an active protection system that ensures that corrosion cannot occur. The ICCP system used on the viaduct is a titanium mesh anode – with a life expectancy of between 70-120 years – fixed on the concrete surface and connected to a power supply, overlayed with concrete. The monitoring of the ICCP system is remote so reduces the requirement to attend the site.
Health and safety, sustainability and community benefits
Our use of phased repairs using ICCP over the demolition and replacement of the viaduct has meant the health and safety risks of a project of this scale have greatly been reduced – we’ve eliminated the need to prop a live carriageway, close roads, introduce speed limits and weight restrictions.
The team has calculated that we’ve also made significant C02 savings in the use of raw materials:
- 98% CO2 reduction for concrete elements
- 99% CO2 reduction for steel elements
- 97% CO2 reduction for timber elements
Collaboration
The team’s collaborative approach has ensured that lessons learnt on the first phase of the project are captured and implemented on future phases.
Partnership working encouraged early involvement between all parties, allowing early review and challenge of design proposals. This allowed the design to be adjusted in the earlier stages of the programme when changes are easier and more cost-effective to implement.
Our design team also worked closely with the site team to identify possible issues with the design and addressed any technical queries arising during construction.