Contex a weapon against corrosion
Hempel has been on the road promoting its solution to the harmful environmental effects on reinforced concrete. Its anti-carbonation coating system Contex is a proven ‘first line of defence’ against corrosion, says the leading paints and coatings manufacturer.
HEMPEL, a global leader in the production and sales of protective and decorative coatings, recently organised a Middle East roadshow as part of its efforts to communicate with specifiers and customers and introduce new solutions to solve certain engineering problems.
The roadshow seminars, held last month (May 4 to 17) in Kuwait, Bahrain and Saudi Arabia (Riyadh, Jeddah and Makkah), covered two topics that concern both civil and architectural interests – concrete protection and colour trends.
Moataz Kamel, marketing manager for Hempel Middle East (West), spoke about concrete protection, focusing on the aggressive environmental elements that concrete is exposed to and the damage that can occur through exposure to these aggressive agents.
He also presented Contex, Hempel’s highly effective solution for the protection of reinforced concrete against these elements.
A proven ‘first line of defence’, Contex is an anti-carbonation coating system that provides proactive protection to concrete against a wide range of possible attacks and in turn protects steel rebar from corrosion, maintaining both the compressive and tensile strengths of the concrete structure.
Says Kamel: “Reinforced concrete, as an engineering material, is widely used in most civil structures. When used in various structural elements, it needs to withstand various loads that the skeleton of the building is subjected to.
“Reinforced concrete consists of concrete mix comprising cement, water and aggregate in addition to steel rebar. After hardening and curing, the concrete mix acts as a passive layer protecting the steel rebar from corrosion. This protection comes mainly due to the alkalinity of the concrete, which exceeds pH12.”
Reinforced concrete in buildings may come under attack from a number of elements in the environment. These include liquid water, intrusion of carbon dioxide (CO2) and chloride ions, and sulphate attack.”
Carbonation
Elaborating on the process of carbonation, he says: “Carbon dioxide ingresses through pores in the concrete and in the presence of liquid water, it reduces the pH value of the concrete down to pH9. This reduced alkalinity makes the media aggressive on the steel rebar, which starts to corrode.
This apart, the CO2 reacts with calcium hydroxide (CaOH3), one of the chemical compounds in concrete, to produce calcium carbonate (CaCO3), which weakens the material and causes spalling of the concrete cover.
“Also when steel rebar corrodes, its cross-section increases, resulting in internal stresses, which in turn causes cracks in the concrete cover. This process leads to cracking and spalling of the concrete cover, which will further expose the steel rebar to the environment.”
Chloride intrusion
The highly alkaline environment of good quality concrete forms a passive layer surrounding the embedded rebar, which normally prevents the steel from corroding. However, chloride ions if present in the concrete facilitate a local breakdown of the passive layer when the pH value is reduced, resulting in pitting of the steel rebar. Pitting is a form of localised corrosion and occurs mainly in the presence of neutral or acidic solutions containing chlorides or other halides.
Other factors
Concrete surfaces may also crack due to various reasons, such as volumetric changes taking place due to drying of concrete; thermal cracks and tension cracks due to tensile stresses, says Kamel.
“These cracks also contribute the process of corrosion by allowing aggressive elements to get inside the concrete section and reach the steel rebar,” he adds.
Contex’s range of acrylic coating systems provides the most comprehensive solution for these problems within the civil industry, providing both water-borne and solvent-borne systems in a wide variety of finishes.
“Contex prevents liquid water, CO2 and chlorides from reaching both the concrete and steel rebar, thus preventing all expected chemical reactions that could cause concrete degradation and initiate steel rebar corrosion,” says Kamel.
At the same time, Contex allows the entrapped humidity to be released from the concrete section, facilitating the breathability of the building.
Finally, Contex has a crack-bridging ability to overcome cracks which may occur on the concrete surface due to previously-mentioned causes. This ability ensures the integrity of the coating system, preventing it from cracking and leaving the concrete section exposed to aggressive environmental effects.
Each of Hempel’s Contex anti-carbonation coating systems has been independently tested and certified by Taylor Woodrow laboratories in the UK, as being able to provide proactive protection to concrete structures against a wide range of possible attacks and defects, he says.
These include chloride intrusion, concrete carbonation, alkali degradation, rebar corrosion, water/vapour entrapment, crack-bridging ability, ultraviolet degradation, and mechanical/impact damage.
Colour trends
As part of the road show, Hempel also focused on the latest colour trends, which will shape the fashion, interiors and many other disciplines during autumn/winter of this year. Mohamed Baitie, regional brand manager, Hempel Middle East (West), presented four main trends to the audience – Contour, Punch, Opal and Roma.
With his presentation, Baitie took the audience on a journey of how the trends were identified before they were finally presented to designers. This was achieved through workshops that brought together selected designers from different industries to create colour palettes to represent the colour trends.
The workshops were conducted by the UK-based Global Colour Research Company, which is one of the leading colour research bureaus in the world in the field of shaping the colour trends globally.
Baitie also went through the concept of every colour trend and its main elements, pointing out however that these trends do not represent certain colour schemes and hence cannot be used directly as colour cards by designers. The four palettes represent the trends of colour, texture, transparency and glossiness, which Hempel takes and translates into its colour proposition through different colour cards that are provided to its customers.
“Hempel as a worldwide leader in the paint industry is keen to base its colour proposition on the latest colour trends created by the most reliable colour research company worldwide,” Baitie concluded.
Hempel has been on the road promoting its solution to the harmful environmental effects on reinforced concrete. Its anti-carbonation coating system Contex is a proven ‘first line of defence’ against corrosion, says the leading paints and coatings manufacturer. …
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