Hunterston Jetty - West Kilbride
More than 100 tonnes of webercem spray DS, one of Weber’s high performance structural concrete repair products, was used in the £1.3m jetty refurbishment contract carried out at the Hunterston B Nuclear Power Station in West Kilbride.
This complex project has been successfully completed by award-winning Balfour Beatty Regional (BBR), who has built a strong skills inventory in this specialist construction and maintenance field with expert capability in hard-to-access site operations. This project was nominated for the Concrete Specialist of the Year Awards 2014 in which BBR was overall winner.
EDF had considered demolition and rebuild as a solution for this jetty as the access problems were initially considered to be too high a safety risk. Offsite trials of its access methods enabled BBR to demonstrate that their process could complete the project safely in this very hostile operating environment.
The jetty serves as a material delivery artery and had been in place since the nuclear plant construction was completed in 1976. Damage to the reinforced concrete was caused by exposure to the fierce weather of the shoreline location and also the tidal power activity below the waterline. Added to this the marine salt had severely corroded the exposed steel reinforcing. The remedial programme required a work platform system that could be raised as water levels rose which required careful planning to match weather and tidal conditions.
webercem spray DS is a ready-to-use, polymer modified, dry-spray cement-based concrete mix containing inert limestone aggregates and dust suppressants. The formulation has been designed especially for dry process spray application to give early strength, reduced rebound and maximum application thickness. Its core application includes repairs to marine structures, jetties, seawalls, dry-docks and concrete offshore platforms. This product also complies with Highways Agency specifications for repairs to highway structures such as flyovers, bridges and parapets. The high build attribute of webercem spray DS enables up to 150mm thickness to be applied in a single pass even on vertical and overhead faces without additional mesh reinforcement.
Hydro demolition was used to breakout the spalled and cracked concrete and this high pressure water jetting system also washed out the surface chlorides and subsequently cleansed the refurbishment. The installation of a Cathodic Protection (CP) system to provide impressed current cover to the reinforcing steel within the repaired concrete will ensure long term performance. webercem spray CP, a low-resistivity, ready-to-use, structural repair concrete was used to embed the sacrificial anodes and for small patch repairs where a more conductive mortar was required.
After installation of the CP system, webercem spray DS concrete was used as an overlay making the substantial structural repairs to the required profiles while forming a new protective cover for the whole structure. Working to a tight 16-week weather window, with divers and the complex tidal schedules, the work was carried out successfully and to the complete satisfaction of EDF.