With the three road bridges of the Rochester Bridge — this includes the Old Bridge, the New Bridge and the Service Bridge — in need of major refurbishment, Metrail carried out concrete repairs on all three bridges as well as expansion joint replacement and bridge deck waterproofing on the Old Bridge and the New Bridge.

  • Challenge
  • Solution approach
  • Technology

  • Execution

  • Result

The challenge

Due to the age and heritage of the structures associated with the bridges, a comprehensive programme of checking and inspection was required. We did this to ensure that all areas requiring attention were identified.
This was also one of the first projects to utilise an NEC4 Contract, in which 78% of our completed works were through variations.
And in addition, the complexity of the programme required the Metrail team on-site to interface with many different stakeholders in order to ensure that at each stage of the works everyone was happy to proceed, without detriment to the programme.

Solution approach

We began our on-site work in July 2019 with concrete repairs to the bridge soffits. Unfortunately, however, the programme was disrupted due to the Covid-19 pandemic and the first national lockdown in March 2020. This led to the programme needing to be rescheduled and a new completion date being agreed upon.

Facts & Figures

Which structures?
The Old Bridge, New Bridge and Service Bridge of Rochester Bridge

Metrail carried out concrete repairs on all three bridges as well as expansion joint replacement and bridge deck waterproofing on the Old Bridge and New Bridge

Concrete repairs to the bridge soffits commenced in July 2019

One of the first projects to utilise an NEC4 Contract, in which 78% of our completed works were through variations

We carried out the following works

1. Concrete Repairs (on all three bridges)

Our first step of concrete repair: the breakout of unsound concrete. This has to be cut to a depth of 10mm for repair mortar and 20mm for repair concrete. Where reinforcing is encountered, this needs to be exposed to the full circumference of the steel. Any signs of corrosion require removal using abrasive equipment, and in some cases where the corrosion is bad, additional bars are added prior to repair. Care was also taken to ensure formwork was secure before repair concrete was placed.
Resin injection repairs turned out to be very minor.

2. Expansion Joint Replacement

(Old Bridge & New Bridge)

Technology - The majority of the joints replaced on the Old Bridge were Type 1, also known as a “plug joint”. Cost effective and maintenance free, the plug joint is a simple expansion joint for highway bridges. On the New Bridge, Type 6 joints were specified. Type 6 joints incorporate a central elastomeric seal inserted into two steel carrier rails. The carrier rails have special sinusoidal-shaped reinforcement welded into the rear face which locks the carrier rails into the nosing mortar.
Execution - When it comes to replacement of the joints, damaged areas need to be cut out and all exposed surfaces primed before the Sentinal EMR rails can be lifted into place. Polystyrene shuttering was used before pouring the nosing mortar which was levelled with the road surface. Safetrack, a proprietary anti-skid finish, was then applied.

3. Bridge Deck Waterproofing
(Old Bridge & New Bridge)

Technology - Eliminator, the GPC Advanced Technologies waterproofing system, is a rapid cure, cold liquid spray applied system based on methacrylate monomers which forms a tough, flexible seamless membrane. In places where asphalt is to be laid, a bond coat — also known as a tack coat — is also applied. Surface preparation and dry conditions are essential for the successful application of the Eliminator waterproofing system.
Execution - After removal of the asphalt wearing surface, Metrail scraped and cleaned the bridge deck as well as carried out any necessary concrete repairs to the surface using Metaset. Fine milling of the surface then ensured that the substrata was clean, dry and structurally sound so that the primer coat could be applied.
As the Rochester Bridge Trust had specified that the waterproofing should mirror the original waterproofing on the bridge, two coats of the Eliminator waterproofing membrane were applied and the bond coat used was SA1030. This is a polymer-modified bond coat which is applied over the waterproofing membrane to provide a very strong bond between the membrane and the hot bituminous road surfacing.


Metrail was honoured to have been awarded this work on such an important and historical structure. The refurbishment of Rochester Bridge provided us with the opportunity to demonstrate our core skills and depth of experience in concrete repairs, expansion joint replacement and bridge deck waterproofing. The impact of Covid-19 on the project was significant, but careful planning and management of resources allowed us to overcome this, and we’re pleased to report that it did not affect delivery of our works and we were able to meet the revised programme.

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