Braefoot Jetty - Fife, Scotland
Located between St. David's and Aberdour, the tanker terminal at Braefoot Bay is a base for the export of liquefied petroleum gas. The terminal consists of two jetties located on the north shore of Incholm Island. The gas is piped to the Mossmoran Plant in Fife direct from the North Sea, broken down to form ethane and then converted into ethylene, the basic hydrocarbon 'building block' of the petrochemical industry. The products are then piped the final three mile journey to the Braefoot Marine Terminal where they are fed into tankers and gas carriers for markets in Europe and the USA. The terminal is operated jointly by Shell Expro and Exxon.The jetty was suffering from increasing levels of deterioration of the reinforced concrete structure due to the relentless corrosive action of the marine salt environment on the reinforcing steel. A remedial plan was developed to carry out repairs and to introduce a cathodic protection (CP) system to greatly enhance the protection level and therefore extend the life of the structure. The plan was prepared by structural engineers from Shell, led by Hans Verheyde, and Balfour Beatty Construction Services UK (BBCS) was awarded the contract.Two major factors had to be accommodated within the repair programme. Firstly, the tidal flow that submerged the lower part of the jetty twice every 24 hours and secondly, the jetty is a fully live and very active transport hub and shipping schedules had to take precedence at all times. Round-the-clock flexible working maintained delivery of the twelve-month project.Saint-Gobain Weber's specialised repair concrete products were specified for the remedial actions on the Braefoot Bay jetty and technical application advice was provided for the active phase of the project. A suspended scaffold was designed and installed which allowed fast access when the tide ebbed so that productivity could be maintained. Traditional techniques were used to breakout the spalled and cracked concrete and to wash out the surface chlorides and clean the existing reinforcement steels.webercem five star repair concrete CP is a shrinkage-compensated, high strength, low resistivity, flowing repair concrete designed for use in conjunction with CP systems. This pre-blended cementitious concrete fully complies with the Highways Agency Specification Class 29F for high-strength flowing concrete for major structural repairs. It contains non-reactive aggregates with a low soluble-alkali cement content which is particularly important where CP is to be used. The rapid strength development and dimensional stability of webercem five star repair concrete CP – which reaches 27N/mm² in 24 hours – was especially valuable in the tidal conditions in Fife. Tight shuttering was used on the wide beam sections of the jetty to take the poured concrete which reached an integral bond with the original concrete. This process reformed the structural integrity using products with proven durability.An innovative CP system using Duogard® hybrid anodes from CPT was installed to protect the steel reinforcement with the anodes fixed into the soffits with a special CPT mortar. Where the CP installation required chases to carry the cabling, webercem HB40 high-build structural repair mortar was used to fill and seal the chases. webercem bondcoat, a polymer-modified, cementitious bonding aid and steel reinforcement primer, was first applied into the chases to ensure enhanced bonding. webercem HB40 is an acrylic-polymer modified, single component mortar and is lightweight with high build qualities. It can be applied in layers up to 75mm thick vertically, and 50mm on overhead soffits, and can be used without formwork. It was then applied onto the tacky webercem bondcoat primer and finished flush to the concrete surface.The Braefoot Bay terminal project has been completed successfully and Dewi Miller, contracts manager, BBCS, is confident that the jetty protection will extend the working life of the structure. "The products we have used are excellent and the application methods have enabled us to deliver a high degree of protection and reinstatement to the concrete structure. Working on a live site in a tidal zone has required a flexible work schedule but the whole project has worked exactly to plan and the client is very pleased with the result. The Weber materials have been the key to achieving this success."