When two listed town centre bridges began to display signs of wear and tear, a proven, long-term solution was required. Sika’s concrete and total corrosion management system was more than up to the challenge.

 

The Mellor Spodden north and south bridges, which span the River Spodden in Rochdale, Lancashire have been a feature on the local landscape since their construction in the early 1900s. The bridge structures comprise reinforced concrete and consist of ferrocrete vaults spanning the watercourse and supported by curtain walls tied to slabs which sit on reinforced concrete piles.  

Spalls and cracks, which were large in places, had begun to appear on the bridges’ soffits and front and rear elevations in part due to the age of the bridges and the occurrence of latent defects such as low concrete cover which enabled conditions to form leading to localised corrosion of the structural reinforcement in the affected areas. In the most deteriorated areas, the bridges’ streel reinforcement had become exposed through expansive corrosion and spalling the cover concrete.

 

Contractors, APA Concrete Repairs Ltd completed a programme of remediation to restore the protective cover to structural reinforcement and improved the durability of the structure overall by preventing further corrosion. As the town’s designated ‘main river’, all access to the riverbed and works required prior approval from the Environment Agency, specific control measures were implemented as part of the planned works to reduce environmental impacts.

SikaCem®-133F Gunite provided the high-performance, cement and fibre -based repair mortar to replenish the ageing, deteriorating concrete soffits. The SikaCem®-133F Gunite was dry spray-applied over a 700m2 area and finished by APA Concrete Repairs to provide a range of finishes sympathetic to the original features and overall style of the bridge.

 

To manage the steel corrosion within the structures, products from Sika’s Total Corrosion Management (TCM) portfolio were utilised. These included Sika® Ferrogard®-903+, a surface-applied, multi-functional liquid corrosion inhibitor. Applied to a 700m2 area of the bridges’ concrete surface, the liquid migrates to the reinforcement through the concrete and forms a protective layer which suppresses and prevents further corrosive activity.  

In addition, where chlorides were high, 150 Sika® Galvashield® XPT galvanic, sacrificial anodes were installed to prevent the formation of new corrosion sites (incipient anodes) adjacent to the repaired concrete. This simple, innovative anode system involves a small, circular-shaped cementitious shell encasing a zinc core which is quickly and easily fastened to exposed steel reinforcement. Once installed, the anode’s zinc core corrodes sacrificially to the surrounding rebar, therefore protecting the rebar.

 

Sam Brooke, Director at APA Concrete Repairs Ltd, said: “SikaCem®-133F Gunite was the ideal material for reinstating patch repairs as well as providing protective cover to reinforcement generally across the bridge in the form of an overlay. SikaCem®-133F Gunite provided a dense concrete with superior adhesion to the parent concrete and was worked by APA’s skilled operatives to provide a sympathetic finish in keeping with the historic appearance of the bridge.”

 

Thanks to the reliable, long-term protective qualities of Sika’s concrete and total corrosion management system, Rochdale town centre’s listed bridges are guaranteed an intended working life of 120 years.