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Flexcrete Coating Proven to Combat Chloride Attack for 27 Years

Independent testing carried out at the VINCI Construction Technology Centre has confirmed that Flexcrete’s Cementitious Coating 851 will provide an effective barrier to chlorides for at least 27 years.

Cementitious Coating 851 is a high performance, two component, waterborne cementitious modified polymer coating which is ideal for the structural waterproofing of reinforced concrete, resisting 10 bar 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.

In 1988, a 2mm thick film of Cementitious Coating 851 was applied to a concrete slice and sealed in a chloride ion diffusion cell in the laboratory at the VINCI Construction Technology Centre and it is still going strong some 27 years (9847 days) later. Tests recently carried out show that the barrier properties of 851 are such that a steady state of flux of chloride ions through the coated concrete has not been attained after a test period spanning 27 years, whereas the control concrete achieved this in just 28 days.

851 is specified on both existing and new structures to waterproof concrete, reinstate concrete cover and provide an effective barrier to chloride ingress, amongst many other challenges typically encountered on buildings, infrastructure and structures in sectors such as the coastal and water industries. It provides an effective alternative to recasting or even demolition of precast and in-situ reinforced concrete, where the cover to the reinforcement has not been achieved to give the durability to attain the specified design life.

A 2mm coating of Cementitious Coating 851 is equivalent to 100mm of good quality concrete and being cement based, it chemically reacts with the substrate to form an integral part and will have a design life equivalent to that of the concrete to which it is applied.  851 can be applied to either green or aged concrete by brush or spray techniques, exhibits minimal hazard during application and is non-toxic when cured. It is CE marked in accordance with BS EN 1504-2, the pan European standard for concrete repair, and it is also backed by British Board of Agrément (BBA), WRAS and London Underground approval. In addition, it is approved under Regulation 31(4)(a) for use in contact with drinking water.

Chris Lloyd, Director of Flexcrete Technologies Limited said:

“Chloride attack is one of the primary causes of damage on reinforced concrete structures exposed to de-icing salts and harsh coastal environments, so we are delighted that Cementitious Coating 851 has been proven to provide at last 27 years’ of effective protection against corrosion of steel reinforcement.

“We introduced 851 back in 1985 and at the time it took the technology of polymer modified waterproofing slurries to new levels of performance. It still remains one of the best performing products available for providing structural protection against chloride attack and has been proven in service on structures both in the UK and further afield, such as Crossrail developments including Tottenham Court Road, Liverpool Street and Paddington Stations and the Gorgon Project in Australia, one of the world’s largest natural gas projects,” he continued.

One other prestigious project is a concrete and steel jetty in the North West of England which is capable of handling vessels up to 65,000 tons. In operation since 1960, Cementitious Coating 851 was specified in 1985 in order to extend the service life of the jetty, as inspection of the 70 supporting pillars had uncovered localised concrete spalling and corrosion of the reinforcement due to chloride attack. An inspection in 2010 confirmed that 851 had fulfilled its function as a waterproof, chloride resistant finish in the tidal environment.

Following the inspection, the Technical Director of a leading Engineering Consultancy stated:

“The application of Cementitious Coating 851 would appear to have been effective in enhancing the durability of the reinforced concrete which had suffered considerable deterioration during the initial 27 years of exposure when the concrete was left without any secondary protection.”

Flexcrete Technologies Limited is the UK’s leading independent manufacturer of technical mortars and high performance coatings. With origins dating back to 1983, the company manufactures a wide range of concrete repair mortars, fairing coats, waterproof cementitious coatings and decorative protective coatings. With its head office and manufacturing complex based in Leyland, North West England, Flexcrete products are available from stockholding distributors all around the UK. The company also has a global presence through international agents and distributors in 65 countries worldwide with export sales accounting for over 50% of its business.