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Concrete repair & protection for Venetian bridge

Flexcrete products have been used to bring an iconic bridge on Clacton seafront back to its former glory.

Concrete repair materials manufactured by Flexcrete Technologies, part of AkzoNobel, were specified to restore the 104-year old Venetian Bridge in Clacton-on-Sea, Essex, in an overall contract valued at £355,000. Carried out on behalf of Tendring District Council, Flexcrete products were applied to the reinforced concrete structure by specialist contractor Prestec UK. The project was one of the council’s corporate priorities for its financial year.

The restoration of the Venetian Bridge comes on the back of another coastal project that Flexcrete products are being used for in Clacton. As part of a huge £4 million makeover spanning several years, four Flexcrete products are currently being used to refurbish 2,500 reinforced concrete columns on Clacton Pier which itself is 146 years old.

Although the Venetian Bridge was regularly maintained, the structure was showing signs of distress in its centenary year and the destructive effects of 100 years of chloride attack became evident. A small section of concrete broke away, resulting in the erection of support scaffolding to temporarily make the bridge safe. Investigations took place to determine the extent of the problem, which discovered that the bridge was no longer waterproof and had resulted in moisture and corrosive salts penetrating into the structure over a lengthy period of time and corroding the steel reinforcement.

A number of different options were considered, including demolishing the structure. Flexcrete products were chosen in order to extend the lifetime of the bridge and retain it as a landmark focal point for visitors to the area. The bridge provides a gateway between the beach and entertainment on Clacton Pier and the town, crossing Pier Gap and allowing visitors a continuous walk along the seafront gardens.

Prestec UK removed all of the defective concrete from the soffits, spandrel and transverse beams, as well as preparing the whole structure using high pressure water jetting. The chosen concrete repair and protection system was designed in consultation with Richard Jackson Consulting Engineers to withstand the aggressive coastal conditions and persistent chloride attack. An essential part of the specification was compliance of all Flexcrete products with BS EN 1504, the pan European standard for concrete repair.

Repair & Protection System Helps Extend Lifespan of Structure

Following the removal of the defective concrete and finishes, Prestec UK applied Flexcrete Steel Reinforcement Protector 841 to the rebars to provide them with a corrosion preventative flexible coating prior to the application of Monomix – a high strength, shrinkage compensated, waterproof cementitious mortar which can be applied by trowel up to thicknesses of 80mm in a single application. Suitable for application to vertical, horizontal and overhead surfaces, Monomix develops exceptional bond strength, excellent tensile and abrasion resistance, high diffusion resistance to acid gases and chloride ions and low permeability to water, even at 10 bar pressure.

Monolevel FC – an engineering quality fairing coat – was then used to fill minor blow holes and defects and provide a fair faced finish. Bond Prime was applied to the complete surface of the bridge before the application of two coats of Monodex Smooth, a highly advanced, waterborne, elastomeric coating which is ideal for the decorative protection of structures and buildings. It provides excellent protection against carbonation, chloride penetration and water ingress, yet allows damp substrates to breathe.

Monodex Smooth is a single component, water-based coating so it is user-friendly and cures without the release of strong odour or hazardous solvents. It is ultra-fast drying, enabling two coat applications on the same day and it can be applied all year round. Available in a range of standard and special colours, magnolia was chosen for this project. Even in harsh climatic conditions, Monodex Smooth demonstrates excellent colour retention and strong UV resistance.