The work follows on from the previous programme and has seen over 300 significant repairs completed at the Power Station over a 6- month period.
With widespread areas of spalled reinforced concrete across the station, the work was planned to mitigate the potential health and safety issues, mitigate any impact on plant reliability and to ensure that there is no impact on on-going nuclear safety.
Causes of the concrete spalling were varied, but principally a combined effect of the age of the buildings involved, their environmental exposure and occasional areas where water ingress had accelerated degradation.
Defective concrete was broken out to allow for exposed reinforcement to be prepared and treated. Flexcrete’s Steel Reinforcement Protector 841 was used to protect the steel reinforcement prior to the application of concrete repair mortars. This flexible coating forms a highly alkaline coating with a degree of elasticity which not only protects the steel from aggressive acid gases, moisture and chlorides, but passivates the steel surface chemically to prevent further rust formation.
A high strength structural repair mortar was used for the repairs. Monomix HD by Flexcrete is a high strength, waterproof, shrinkage compensated, standard density mortar with good abrasion resistance.
For the structural waterproofing, a cementitious coating was used. Cementitious Coating 851 by Flexcrete is a modified polymer coating. It provides chloride protection and enhances the durability of reinforced concrete by reinstating effective cover to achieve the specified design life.
A Sika Liquid Plastics glass reinforced Decothane Ultra System was installed to waterproof a high-level bund within the station and protect from seawater ingress. This replaced the previous coating which had cracked and failed, providing a waterproof membrane. Carbon fibre wrapping was also used to strengthen structures as part of the programme.
All concrete repair works were completed and have a fifteen-year service life guarantee, to satisfy the operational requirements of the Station. The spalling concrete remediation repairs are passive in nature and will not require any maintenance.
All repairs were completed in full accordance with BS EN 1504. All of CSC Services’ operatives are qualified in the repair and protection of Reinforced Concrete structures in accordance with this standard.