Kingston Wharf, Isle of Wight

High performance concrete repair products by Weber have been used by Prestec UK Limited, Staffordshire, specialists in structural concrete repairs, in the remediation and protection of two commercial shipping wharves at Kingston in East Cowes. Originally, both wharves used for the management and supply of coal to the gas works and power stations.

In recent years, fuel oils of all descriptions have been coming ashore. Now, nearly 100% of all the island's petrol, diesel and fuel oils needed to sustain life and commerce on the Isle of Wight arrive at Kingston Wharf. Built in the 1950s, Kingston Wharf reached a state of disrepair with severe marine salt corrosion of the steel used in the reinforced concrete construction. An urgent remedial project has been undertaken by the Cowes Harbour Commission to safeguard this vital artery and more than 60 tonnes of webercem spray DS repair concrete has been used to repair and reinstate the wharf structure. Islanders can now rest assured that this facility will be protected for the next 20 or more years.

Kingston Wharf was acquired by Cowes Harbour Commission in 2012 and the largest commercial tenants are Isle of White Aggregates and Isle of Wight Fuels. Many other smaller marine businesses are located within Kingston Wharf including Cowes Harbour Commission's own boatyard and Marine Services division as well as marine engineers, boat builders and varied yachting services. The main activity of volume importation is the shipments of crushed limestone aggregates for construction and is the essential fuel supply route. The £600,000 repair project was designed to protect this valuable infrastructure for years to come.

Cowes Harbour Master, Capt. Stuart McIntosh commented: "When we acquired Kingston Wharf in 2012, one of the primary objectives was to safeguard a site of strategic importance not only to Cowes but to the whole of the Island. This ensured that commercial wharfage remained available for the good of the River Medina and local businesses. The wharf itself is one of the only facilities on the Island capable of landing bulk materials, such as aggregates, and facilitates the import of around 98% of the Island's oil by ship."

The Southampton office of consulting engineers Ramboll carried out the structural survey of the wharf and carried out sample testing of the structure where straightforward access was possible. Ramboll then prepared the tender documents reflecting the scope of works.

Whilst the lowest tides enable access from the foreshore, a slung scaffold structure at the correct working height was installed to enable working in tidal windows. The poor condition of the structure required hydro-demolition with high pressure water jetting breaking the defective areas of concrete and cleansing the remaining substrate and reinforcing steel. The substantial remedial works required a strong sequencing policy to maximise productivity. From the initial surveys the volume of defective concrete was found to be much higher than estimated from the initial surveys.

The project has always included the installation of a Cathodic Protection (CP) system using Patchguard® anodes from CPT to protect the steel reinforcements. The anodes were fixed into the soffits and beams. Weber's specialist concrete repair products were selected to facilitate this major repair. webercem spray DS, a ready to use, polymer modified, cement based concrete mix with inert limestone aggregates and dust suppressants is especially designed for dry process spray application to give high early strength, reduced rebound and maximum application thickness. Up to 150mm thickness can be applied in one pass on vertical or overhead faces without any additional mesh reinforcement. webercem spray DS is designed for use in conjunction with CP systems and complies with the Highways Agency Specification Class 29F for major structural repairs. The rapid strength development and dimensional stability of webercem spray DS with an initial set in 2-3 hours was especially valuable in the tidal conditions at Cowes. webercem spray DS gives a compressive strength in seven days of 49.8MPa.

webercem pyratop, a rapid strength-grain repair concrete for thin bonded repairs, was used to resurface concrete roadways and ramps on the wharf. It provides 25N/mm² compressive strength in just one day and conforms to BS EN 1504-3 meeting the requirements for a Class R4 repair product.

Throughout the project operations, the Ramboll site team led by Marcus Gillard, worked alongside Prestec to supervise construction and monitor performance and quality KPIs. "This pro-active and co-operative working process ensures that the project completion delivers the correct result and eliminates subsequent difficult, and extremely expensive, remedial work. It's a right-first-time process that is a benefit to all parties," said Mr Gillard.

The now fit-for-purpose wharf structure is back in full operation. Cowes Harbour Commission marine services manager, Barney Sollar, is full of praise for the contracting parties. "The refurbishment of the waterfront at Kingston has been technically challenging, however, the works have progressed smoothly with the full co-operation of our main tenants, Isle of Wight Fuels and Isle of Wight Aggregates. We have kept the wharf operating throughout and, in the main, managed to time ship arrivals and discharge at high tide so that the construction team can get back to work at low tide. Prestec have run a seven days-a-week operation so the project has run to schedule. I'm confident we had the right partners for this project and the right materials from Weber," said Mr Sollar.