Gulf Construction Online - Flexcrete promises ultimate protection

Protective Coatings

Flexcrete offers durable and cost-effective solutions.

Flexcrete promises ultimate protection

01 January 2008

Flexcrete Technologies, a specialist manufacturer of Portland cement-based protective coatings, claims to offer the ultimate protection for reinforced concrete from both the hot, humid atmosphere in the Middle East and the region’s aggressive sulphate-bearing ground conditions.

This protection is afforded by its unique range of thin film cementitious coatings, which offer durable and cost-effective solutions to a number of challenges that are commonly encountered in modern-day construction.
“We have modern manufacturing facilities in the UK and generate half of our turnover from exports, with our unique coating formulations having become a firm favourite with engineers facing concrete durability issues throughout the Gulf,” says W Graham James, director of Flexcrete Technologies.
The Flexcrete brand has gained prominence with a state-of-the art polymer-modified concrete repair system.
However, the range of technical mortars was quickly followed by innovative cementitious coating formulations with class-leading performance with respect to protection from chloride ingress, structural waterproofing and diffusion resistance to gases such as oxygen and carbon dioxide.
According to a Flexcrete spokesman, the start of its research and development programme (R&D) coincided with the commercial introduction of microsilica, giving a distinct advantage over other established manufacturers who were faced with the challenge of incorporating this exciting new raw material into existing products.
Chloride attack of concrete is an area of increasing concern with more and more structures showing the tell-tale signs of deterioration. “Flexcrete has a fast growing reputation in the field of chloride protection, and it is now more than 19 years since chloride ion diffusion testing began on Cementitious Coating 851 at Taylor Woodrow Technology (formerly Taywood Engineering). In contrast to the control concrete, which permitted the diffusion of chloride ions within the first month of testing, the concrete treated with 2 mm of Cementitious Coating 851 continues to exhibit total resistance to chlorides – performance which is unrivalled by any other coating available on the world market,” the spokesman claims.
“This technology has been adopted for several high-profile contracts in the Middle East where the ultimate in chloride protection is required. In Qatar alone, more than 200 tonnes of Cementitious Coating 851 have been supplied to the Q-Chem II ethylene derivatives plant, where the design engineer wanted guaranteed protection from aggressive saline ground conditions to avoid costly repairs and disruption during the design life of the structure. It has also been applied over many kilometres to the wave protection wall at the Corniche in Doha. Prior to the reinstatement and protection works specified by Halcrow, the sea wall was in an advanced state of deterioration, but many years of maintenance-free service can now be anticipated,” he point out.
Highlighting some of the benefits of the system, the spokesman says: “One clear advantage is that application on to damp concrete is encouraged, immediately eliminating one of the biggest problems faced with traditional coating systems during tight construction programmes. In fact, Flexcrete also recommends its 851 system for slipformed structures because of the excellent bond achieved to green concrete and the significant cost benefit of applying a coating as the form is raised, providing both long-term chloride protection and early age curing in a single treatment.”
A major factor determining the durability of reinforced concrete structures is the effectiveness of the cover to the reinforcement with respect to depth and quality. The role of concrete cover is primarily to protect the reinforcing steel from corrosion by maintaining an alkaline environment and preventing the ingress of the common agents for corrosion. While the cover concrete can generally be disregarded when calculating the load-bearing capacity of reinforced concrete elements, failure to achieve adequate cover for prevalent exposure conditions can be potentially disastrous. If ignored, low cover will lead to a legacy of expensive maintenance and the design life of the structure will not be met.
“Historically, partial demolition and recasting has been the only viable option for addressing low cover – a process that is costly, disruptive and time consuming. Now, the easiest and most cost effective way of reinstating cover is with brush or spray application of a cementitious coating. Extrapolation from the oxygen diffusion coefficient demonstrates that from a standard 2 mm thickness of Cementitious Coating 851, the equivalent of close to 70 mm of additional concrete cover is conferred, giving complete assurance that the reinforcing steel is correctly protected throughout its design life,” the spokesman states. “Similarly, an excellent barrier to carbonation is provided by using Cementitious Coating 851. The equivalent air layer thickness achieved from the 2 mm film is 5,200 m, over 100 times better than the acknowledged minimum standard for an anti-carbonation coating. Cementitious Coating 851 is also highly waterproof with tests showing it is impermeable even when subjected to a 100-m hydrostatic head.”
As the coating does not release solvents, application can be undertaken in confined areas.
“Superior performance characteristics, ease of use and reliability are additional important hallmarks of this environmentally-friendly technology,” the spokesman concludes.