Protection of concretes against chemically aggressive environments

• Author(s): Aguiar, J. L. Barroso de ; Camões, Aires ; Moreira, Pedro M.
• Date: 2008
• Persistent ID: http://hdl.handle.net/1822/12864
• Origin: RepositóriUM - Universidade do Minho
• Subject(s): Silicone hydrophobic agent; Acrylic coating; Epoxy coating; Protected concrete; Chemical attack
• Document Type: Part of book or chapter of book
• Language: English

Description

It is now accepted that the durability of reinforced concrete depends mainly on the composition and properties of the concrete surface layer. This layer, sometimes with a thickness close to the cover of the reinforcement, is most of the times the only responsible for the corrosion protection of the reinforcement. Surface treatments act as a barrier between the environment and the concrete. They prevent or retard the entry of harmful substances such as water, chlorides, etc.. A lot of research is made on water repellent treatment of building materials, as well as on the effect of these agents on barrier properties. Four international conferences were dedicated to the subject, of which the first took place in Delft in 1995, followed by Zürich (1998), Hannover (2001) and Stockholm (2005). Barrier properties are discussed and surface coatings with appropriate “barrier” characteristics can cut off the transportation path into concrete. The European standard EN 1504-2, establishes as a minimum requirement for the coated concrete ingress that the capillary absorption and the water permeability coefficient should not exceed 0.1 kgm-2h-0.5 and the CO2 permeability should at least correspond to a sD (thickness of air layer with equivalent diffusion) value of 50 m. With a wide range of hydrophobic agents and coatings available in the market, it becomes extremely difficult to choose the right type of these products, since similar generic types are known to possess considerably different diffusion characteristics. The performance of the available generic types under different service conditions needs to be studied. There is also a need to develop performance criteria for evaluation of concrete coatings and guidelines for the selection of appropriate products for various exposure conditions.