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Hinkley Point B concrete repairs

AkzoNobel’s range of Intercrete concrete repair materials have been used by specialist contractor CSC Services to complete the 2018 Concrete Spalling Remediation Programme at Hinkley Point B Power Station for client EDF Energy.

The Intercrete range was expanded following AkzoNobel’s acquisition of Flexcrete Technologies Ltd in July 2017 with Flexcrete products becoming known as Intercrete, part of the International brand. The concrete repair work has involved the completion of more than 300 significant repairs at the power station over a six-month period. This follows on from the 2017 programme undertaken by CSC Services.

Hinkley Point B is a nuclear power station located near Bridgwater in Somerset. Construction began in 1967 and Hinkley Point B comprised the first Advanced Gas-Cooled Reactor to generate electricity to the grid in the UK. It now produces up to 965 megawatts of electricity, enough to meet the needs of more than one million homes. With around 535 full-time EDF Energy employees, plus over 220 full time contract partners, based at Hinkley Point B, the station is expected to enter decommissioning in 2023.

With widespread areas of spalled reinforced concrete across the power station, the work was planned to mitigate any potential health and safety issues, alleviate any impact on plant reliability and to ensure that there is no impact on ongoing nuclear safety. The concrete had spalled due to the age of the buildings involved and their environmental exposure, as well as occasional areas where water ingress had accelerated degradation.

Durable Concrete Repair & Protection System

Defective concrete was broken out to allow for exposed reinforcement to be prepared and treated. Intercrete 4871, formerly known as Steel Reinforcement Protector 841, was used to protect the steel rebars prior to the application of Intercrete concrete repair mortars. Intercrete 4871 forms a highly alkaline coating which not only protects the steel from aggressive acid gases, moisture and chlorides, but passivates the steel surface chemically to prevent further rust formation.

Intercrete 4801, formerly known as Monomix HD, was used for the concrete repairs. Intercrete 4801 is a high-strength, waterproof, class R4 structural repair mortar with outstanding abrasion resistance and is suitable for the structural repair, rendering and profiling of vertical, overhead and horizontal surfaces. It is easily trowellable, has excellent low sag properties and can be applied up to thicknesses of 80mm in a single application.

The high bond strength of Intercrete 4801 exceeds the tensile strength of concrete and its dense matrix offers low permeability to water, even at 10 bar pressure, and very high diffusion resistance to acid gases and chloride ions. Non-toxic when cured, the product is supplied as a single component system ready for on-site mixing and use, requiring only the addition of clean water.
For the structural waterproofing, Intercrete 4841 was specified. Formerly known as Cementitious Coating 851, Intercrete 4841 is a high performance, two component, waterborne cementitious modified polymer coating which provides reinstatement of effective cover on precast and in-situ reinforced concrete, enhancing durability to achieve specified design life. A 2mm application of Intercrete 4841 is equivalent to 100mm of good quality concrete. Being cement based, it chemically reacts with the substrate to form an integral part and has a design life equivalent to that of the concrete to which it is applied.

Intercrete 4841 resists positive and negative pressure under a 100-metre head. It forms a hard, highly alkaline coating which not only protects concrete from the effects of aggressive acid gases, moisture and chlorides, but also has greatly enhanced chemical resistance. Independent testing carried out at the VINCI Construction Technology Centre in Bedfordshire has confirmed that Intercrete 4841 will provide an effective barrier to chlorides for at least 30 years.

All concrete repair works were completed by CSC Services with a 15 year service life guarantee, to satisfy the operational requirements of Hinkley Point B Power Station. Designed to require no maintenance during the lifetime of the repairs, all work was carried out in accordance with BS EN 1504, the pan European standard for concrete repair.