‘Out of Joint’ – Managing Corrosion in Bridge Joints

Based on the paper 'Investigation, Mitigation and Management of Corroding Bridge Joints in Leicestershire', presented at the Highways Maintenance Engineers Conference at Nottingham University, 7-9th September 1998.

Bridge structures are designed to last decades, but one persistent issue continues to threaten their durability: corrosion caused by salt-laden water leaking through joints. Over time, this accelerates the deterioration of embedded steel reinforcement, putting structural integrity at risk. A project on the M1 motorway in Leicestershire, UK, offers a compelling case study in how innovative engineering, specifically impressed current cathodic protection (ICCP), can address this challenge effectively and with minimal disruption.

The Problem: Hidden but Severe Corrosion

Bridges built in the 1970s, though innovative for their time, included design features like half-joints and concrete hinges that have proven vulnerable. Water carrying de-icing salts seeps through joints, reaching deep into the structure and triggering corrosion.

Inspections revealed:

Cracking and spalling concrete
Rust staining on soffits (undersides)
Severe pitting corrosion in reinforcing bars
High chloride concentrations deep within joints

In some cases, corrosion was occurring in areas not detectable through standard surface inspections, making the problem even more dangerous.

Engineers conducted detailed testing on the River Avon Viaduct, including:

Half-cell potential mapping (surface and deep-hole)
Chloride concentration analysis
Targeted drilling into critical joint areas

These tests confirmed that corrosion was most severe deep within the half-joints, especially near key structural interfaces.

To stop corrosion at its source, engineers implemented ICCP, a technique that applies a small electrical current to the steel reinforcement, preventing it from corroding.

A major challenge was delivering protection deep within the structure. The solution came in the form of conductive ceramic “discreet anodes”, inserted into drilled holes. This approach allowed engineers to target the most vulnerable zones directly, rather than relying on surface treatments.

The system didn’t stop at installation. It included a networked monitoring system that allows engineers to track corrosion rates in real time, adjust electrical current remotely, receive alerts if performance drops and manage multiple bridges from a central location. This marked an early move toward digitally managed infrastructure.

One of the most impressive aspects of the project was execution. Most work was done from beneath the bridge with minimal impact on motorway traffic and the system fully operational within schedule.

The ICCP system proved highly effective:

Successfully halted corrosion in critical areas
Provided long-term protection with minimal maintenance
Cost less than traditional repair methods
Scalable to other bridges across the network

Following this success, similar systems were installed on additional bridges along the M1.

Why This Matters?

This project demonstrates a shift in infrastructure management.

From reactive repairs → to proactive, long-term protection
From manual inspections → to smart, remote monitoring
From disruptive works → to minimal-impact solutions

As infrastructure ages worldwide, approaches like ICCP offer a sustainable and cost-effective way to extend the life of critical assets.

Read our full article, ‘Out of Joint’, published by Concrete Engineering International here.

Preventing an Achilles Heel

Surface-applied corrosion inhibitors are emerging as a flexible alternative to cathodic protection for reinforced concrete structures.

Corrosion of reinforced concrete remains one of the most persistent maintenance challenges facing bridge owners and infrastructure managers. While impressed current cathodic protection (ICCP) systems have long been regarded as a proven method of corrosion control, surface-applied corrosion inhibitors (S-ACIs) are increasingly being adopted as a complementary or alternative strategy.

A corrosion inhibitor is any substance which, when introduced into an environment at relatively low concentration, reduces existing corrosion and limits the risk of future deterioration. Although inhibitors have been widely used for decades in the petrochemical and transportation sectors, their use within reinforced concrete structures is comparatively recent.

The protection provided by reinforced concrete relies heavily on the highly alkaline environment surrounding the embedded steel reinforcement. Under normal conditions, this alkalinity maintains a stable passive oxide film on the steel surface, preventing corrosion. However, when carbonation or chloride contamination reduces alkalinity, corrosion can initiate, leading to cracking, spalling and eventual loss of structural capacity.

S-ACIs operate by interfering with the electrochemical corrosion process occurring between anodic and cathodic sites on the reinforcing steel. Depending on the formulation, inhibitors may act anodically, cathodically or as mixed inhibitors. The systems evaluated in this study were mixed inhibitors, designed to suppress both anodic and cathodic reactions simultaneously through the formation of a protective film on the steel surface.

Because mixed inhibitors do not necessarily create a significant shift in corrosion potential, the study emphasised the importance of monitoring corrosion rate rather than relying solely on half-cell potential measurements. Embedded corrosion rate sensors developed by C-Probe Technologies were used alongside the AchillesIES remote monitoring system to measure steel loss over time and evaluate treatment performance.

Field applications

Three bridge structures managed on behalf of the Highways Agency were monitored to assess the effectiveness of S-ACI treatments.

Twyford Bridge, Nottinghamshire

At Twyford Bridge, S-ACIs were trialled on suspended bridge slabs alongside an ICCP installation. Two products, Sika Ferrogard and Flexcrete MCI 2020, were spray-applied to opposite sections of the bridge soffit.

The soffit application proved difficult because of poor absorption into the concrete surface. Nevertheless, areas associated with newly grouted repairs showed significant reductions in corrosion rate, suggesting that diffusion pathways through repaired concrete improved inhibitor penetration.

Wansford Bridge, Cambridgeshire

Wansford Bridge formed part of a larger pilot study comparing ICCP systems and S-ACI technology. The inhibitor was applied to the deck soffit in two treatment coats.

Unlike Twyford, the inhibitor successfully diffused through the concrete cover and produced measurable reductions in corrosion activity. The project demonstrated that S-ACI treatments can perform effectively when the concrete condition allows adequate penetration to the reinforcement level.

Ranby Canal Bridge, Nottinghamshire

Ranby Bridge provided the most comprehensive assessment of S-ACI performance. The bridge structure, including abutment walls and soffits, was treated over approximately 500m².

In areas undergoing concrete repair, the inhibitor was applied directly to exposed reinforcement before patch repairs were completed. Additional surface treatment was then applied to surrounding concrete to create a long-term reservoir of inhibitor and reduce the risk of incipient anode formation adjacent to repair zones.

This direct-to-steel application produced the most significant performance improvements, with corrosion rates reduced by as much as 100-fold in some monitored locations.

Key findings

The study demonstrated that surface-applied corrosion inhibitors can significantly reduce reinforcement corrosion in reinforced concrete structures when correctly applied and monitored.

However, performance depends heavily on several factors:

The inhibitor must successfully reach the reinforcement surface.
Concrete porosity and cover depth strongly influence diffusion.
Moisture and oxygen availability affect corrosion activity and inhibitor demand.
Severely corroded structures may require excessive quantities of inhibitor to remain effective.

Direct application onto exposed reinforcement during concrete repair proved particularly effective, while surface-applied treatments alone achieved more moderate but still meaningful reductions in corrosion rate.

The study also highlighted the importance of long-term corrosion monitoring. Without reliable monitoring systems, infrastructure owners cannot accurately assess treatment effectiveness, determine reapplication intervals or optimise maintenance strategies.

Conclusion

Surface-applied corrosion inhibitors are not a universal replacement for cathodic protection, but they offer a flexible and potentially cost-effective addition to the corrosion management toolkit for reinforced concrete structures.

Where conditions are favourable, S-ACIs can extend service life, reduce corrosion rates and enhance the durability of repair works, particularly when used alongside embedded monitoring systems and targeted repair strategies.

The projects demonstrated that successful corrosion prevention relies not only on the treatment itself, but also on understanding how inhibitors interact with the concrete environment over time. Continuous monitoring remains essential to ensuring long-term performance and informing future maintenance requirements.

Read our article ‘Preventing an Achilles Heel’, published by Concrete Engineering International

Decarbonization of Cathodic Protection for the Built Environment

26th October 2023

Decarbonization of Cathodic Protection for the Built Environment

View our LoCem® product range, our low carbon answer to decarbonizing cathodic protection.

Repurposed industrial waste materials are offering a lower-carbon future for cathodic protection systems in reinforced concrete and masonry structures.

As industries worldwide respond to increasing pressure to reduce carbon emissions and meet net-zero targets, corrosion protection technologies are also undergoing significant change. Cathodic protection (CP), long recognised as one of the most effective methods of preserving reinforced concrete and steel-framed structures, has traditionally relied on non-renewable materials and energy-intensive manufacturing processes.

A new generation of sustainable alkali-activated cementitious materials (AACMs), often referred to as geopolymers, is now being developed to reduce the environmental impact of CP systems while maintaining long-term durability and performance.

The approach centres on repurposing industrial waste streams from sectors such as steel production, mining and fossil fuel generation to create conductive cementitious materials capable of functioning as both repair mortars and cathodic protection anodes.

Moving beyond traditional cathodic protection materials

Conventional sacrificial anodes used in cathodic protection systems gradually corrode during service and cannot be recycled once consumed. Similarly, impressed current cathodic protection (ICCP) systems often depend on titanium substrates coated with rare earth metal oxides, materials associated with significant environmental and resource pressures.

At the same time, ordinary Portland cement remains a major contributor to global carbon emissions, accounting for approximately 8% of worldwide CO₂ output.

AACMs offer an alternative route. Produced through ambient blending rather than high-temperature processing, these materials can reduce carbon emissions by more than 90% when compared with conventional Portland cement production.

In addition to their sustainability benefits, AACMs demonstrate strong engineering performance, including high compressive and flexural strength, low shrinkage, excellent chemical resistance and fire resistance exceeding 1,200°C.

Conductive geopolymer anodes

One of the most significant developments is the use of conductive AACMs as cathodic protection anodes.

The highly alkaline nature of the material allows it to activate zinc galvanic anodes and support impressed current systems while also functioning as a structural mortar or concrete. The material can therefore be sprayed, cast, chased into bridge decks or applied within masonry joints, allowing it to integrate directly into repair and preservation strategies.

Laboratory testing demonstrated that the material could support protection current densities substantially higher than those typically required for reinforced concrete structures before acid generation became problematic.

This stability provides confidence for long-term use at lower operational current densities and supports the durability of the overall protection system.

Extending the life of existing structures

The technology has already been applied to several existing structures in both the United Kingdom and the United States.

Edinburgh parking structure

An underground parking structure in Edinburgh utilised a combination of repair strategies designed around condition assessment data and risk profiling.

Conductive geopolymer ICCP anodes were chased into parking decks and sprayed onto structural beams and walls, while galvanic zinc anodes activated by AACM mortars were incorporated into concrete repairs.

Additional areas were treated with surface-applied corrosion inhibitors before waterproofing systems were installed.

The entire structure was divided into 44 controllable cathodic protection zones, alongside additional monitoring zones used to assess corrosion inhibitor performance and future maintenance requirements.

The project aimed to extend the service life of the structure by at least 25 years while significantly reducing embodied carbon compared with demolition and reconstruction.

Masonry-clad steel frame buildings

The technology has also been adapted for transitional steel frame buildings dating from the early twentieth century.

These structures, commonly found in major cities, often suffer from corrosion of embedded steel sections concealed behind brick, stone or terracotta cladding. Corrosion products expand over time, causing cracking, displacement and eventual structural instability.

At a major property on Park Avenue in New York City, conductive anode systems were installed behind terracotta cladding to protect corroding steel elements at upper levels of the building.

The modular nature of the power, monitoring and control systems allows future expansion across additional areas of the structure as required.

Cathodic preservation in new construction

The article also highlights the advantages of incorporating cathodic protection during the construction phase itself.

In so-called cathodic preservation systems, modular anode units manufactured from sustainable AACM materials can be attached directly to reinforcement before concrete placement.

These units are interconnected through plug-and-play wiring systems linked to remote monitoring and control equipment. Concrete can then be cast in-situ or precast around the protected reinforcement.

Research suggests that incorporating cathodic protection at the point of construction can provide significantly enhanced durability and resilience throughout the structure’s intended design life.

Monitoring and service life management

A key aspect of the systems described is the integration of embedded corrosion monitoring technology.

Remote monitoring systems allow engineers and asset owners to track corrosion rates, assess protection performance and estimate future service life without requiring frequent site visits.

This continuous monitoring capability provides owners with measurable evidence of performance while also reducing maintenance-related travel and operational carbon impacts.

Conclusion

The development of sustainable conductive geopolymer materials represents a significant step towards decarbonising cathodic protection for the built environment.

By repurposing industrial waste streams into functional repair and protection materials, these systems offer the potential to reduce embodied carbon, preserve existing structures and support long-term infrastructure resilience.

The projects highlighted demonstrate that sustainable cathodic protection systems can provide effective corrosion control across a range of reinforced concrete and masonry applications while contributing to broader environmental and net-zero objectives.

Combined with integrated remote monitoring and service-life assessment technologies, such systems may form an increasingly important part of future asset management and structural preservation strategies.

Read our article ‘Decarbonization of Cathodic Protection for the Built Environment’, published by Materials Performance Magazine.

Predicting Service Life from Site-Accessed Corrosion Rate Data

25th October 2023

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