Organic coating, concrete

F ie 14.1 Schematic representation of the different types of surface treatment of concrete (o) organic coating, (fc) pore-lining treatments, (c) pore-blocking treatments, (d) thick cementitious coating, shotcrete or rendering, (6)... 

Organic coatings are used to block the penetration of carbon dioxide or chloride ions. They form a continuous polymeric film on the surface of the concrete, of a thickness ranging from 100 to 300 pm. The binder can already be present in the liquid paint as a polymer, or the polymer can be formed due to chemical reactions between monomeric components that are mixed just before application. Modem coating systems are usually built up of several layers applied consecutively. They are compatible with the alkalinity of the concrete and are based on various types of polymers (e. g. acrylate, polyurethane, epoxy), pigments and additives, and are made suitable for application by the addition of solvents or diluents. 

Organic coatings may vary from very dense to rather open for water vapour. A dense coating (ideally without flaws), based on epoxy, polyurethane or chlorinated rubber polymers, may block ingress of aggressive species. Nevertheless, the presence of such a layer strongly hinders the evaporation of the moisture that is present in the concrete at the time of treatment. This situation can lead to loss of adhesion to the concrete and thus to a loss of effectiveness of the coating. 

The anodic process can be stopped by applying a coating to the reinforcement that acts as a physical barrier between the steel and the repair mortar. For this purpose only organic coatings, preferably epoxy based, should be used. Protection is entirely based on the barrier between the reinforcement and the mortar, and passivation of steel cannot be achieved because contact with alkaline repair material is prevented. This method should be used to protect depassivated areas of the reinforcement only as a last resort, i. e. when other techniques are not applicable and only for small specific applications [1,4]. It may be used, for instance, when the thickness of the concrete cover is very low and it is impossible to increase it to the proper level, so that the repair material cannot provide durable protection to the embedded steel. 

The sulphur oxidizing bacteria can produce up to nearly 10% sulfuric acid, which is highly corrosive to metals, coatings, ceramics, and concrete. Other bacteria can produce formic and succinic acids, which are also harmful especially to some organic coatings (52). 

Floating platforms are generally protected by CP (sacrificial anodes or impressed current) combined with a high-quality paint system. Pipelines with an organic coating and an external concrete coating are also protected by sacrificial anodes. 

Keywords concrete surface, post-treatment, organic coating, XPS, FTIR, Raman... 

The CEN standard states in its scope that it refers to atmospherically exposed normal reinforced and prestressed concrete as uncoated and organic coated reinforcement. It is more detailed than the NACE standard (34 pages vs. 12) with far more on the assessment and repair of the structure and installation procedures. The criteria are buried in Section 8 of the standard. 

Saponification s9- pa-n9- fi [F saponifier, fr. L sapon-, sapo (1821) v. (1) Alkaline hydrolysis of fats whereby a soap is formed more generally, the hydrolysis of an ester by an alkah with the formation of an alcohol and a salt of the acid portion. (2) The decomposition of the medium of a paint or varnish film by alkah and moisture in a substrate, e.g., new concrete or fresh plaster. Saponified paint may become sticky and discolored. In severe cases, the film may be completely liquefied by saponification. Loss of adhesion may occur as a saponified layer develops next to the substrate. Morrison RT, Boyd RN (1992) Organic chemistry, 6th edn. Prentice-Hall, Englewood Chffs, NJ. Wicks ZN, Jones FN, Pappas SP (1999) Organic coatings science and technology, 2nd edn. Wiley-Interscience, New York. 

Guide to Specifying Coatings Conforming to Volatile Organic Compound (VOC) Content Requirements Guide for Coating Concrete... 

Experience in Great Britain (Sherwin, 1954) indicates that good-quality engineming brick without frogs, bonded with a latex hydraulic-type cement, is the most satisfactory type of massive construction material for silicon tetrafluoride-absorption towers. In the United States, the towers are more commonly constructed of FRP or wood, with or without a protective organic coating. Tower basins and sumps are usually constructed of conventional port-land-cement concrete. This material is apparently protected fiom severe attack by the precipitation of silica and other conqiounds in the pores as a result of the initial reaction between fluosilidc acid and constituents of the cement... 

Lead is relatively easily corroded where acetic acid fumes are present and under such conditions it either should not be used or should be efficiently protected. Generally, any contact between lead and organic material containing or developing acids will cause corrosion for instance, unseasoned wood may be detrimental. Trouble from this cause may be prevented by using well-seasoned timber, by maintaining dry conditions, or by separating the lead from the timber by bitumen felt or paint. Lead is also subject to attack by lime and particularly by Portland cement, mortar and concrete, but can be protected by a heavy coat of bitumen. A lead damp-proof course laid without protection in the mortar joint of a brick wall may become severely corroded, especially where the brickwork is in an exposed condition and is excessively damp. 

Substrates protected from different environmental conditions basically include the metals (steel, zinc, aluminum and copper), inorganic materials (plaster, concrete and asbestos), and organic materials (wood, wall-board, wallpaper and plastics). Metals may be surface coated to improve their workability in mechanical processing. 

These novel organic polymers were not developed solely for the CW or BW treatment market but are for much wider application. These same value-adding process additives are regularly incorporated into products for industrial and domestic cleaning, concrete, pulp and paper, metal finishing, paints and surface coatings, wastewater, seawater distillation, drilling muds, secondary oil-recovery, plastics extrusion, fibers, rubbers, and a host of other areas. 

Various forms of macro- and microelements differ in their ability to migrate and redistribute among the soil profile. The elements contained in clastic minerals are practically immobile. The elements, bound to finely dispersed clay minerals, are either co-transported with clay particles, or are involved in sorption-desorption processes. Part of the elements are found in concretions and also in very thin coating films of hydrated iron oxides some elements make a part of specially edaphic organic compounds. 

Coating compounds are used to cover the surfaces of many materials from plastic to paper to fabric to metal to concrete and so on. Many plastics produced are consumed as coating materials, including paints, primers, varnishes, and enamels. Metals may be surface coated to improve their workability in mechanical processing. Substrates protected from different environmental conditions basically include the metals (steel, zinc, aluminum, and copper), inorganic materials (plaster, concrete, and asbestos) and organic materials (wood, wallboard, wallpaper, and plastics). Different technical developments continue to occur in the... 

---