Steel and concrete structures are often exposed to many adverse conditions which are not conducive to their performance parameters. They require to be protected with protective coatings.
These coatings are of many types. Stubborn coatings, sacrificial coatings and few more of them.
The aggressive corrosive conditions are on their steep rising trend. They are often found capable of severely and seriously deteriorating the concrete and steel structures. Conventionally designed protective coatings which are commensurate with their ultimate functional needs; also might fall short at times in their performance and hence they need very precise and appropriate reinforcement.
The most commonly used reinforcement of such heavy duty coatings is fiber. Carbon fiber, glass fiber and polypropylene fibers are normally used for reinforcing the protective coatings. All these fibers have their specific function according to their material properties.
Carbon fibers are the most versatile of all the fibers as listed above. They have high inherent strength and excellent inertness to majority of variety of chemicals with corrosive v=magnitude for concrete and steel. At times, carbon fibers replace steel bars which are used for concrete reinforcement. Reinforcing of protective coating with carbon fibers is a unique technique which requires proper engineering for their blending with the coating.
Carbon fiber reinforcement
Similarly glass fibers do have high strength and fairly good chemical resistance to many corrosive chemicals. Glass fibers of appropriate density are to be selected depending upon the ultimate functional need of glass fiber reinforcement. Glass fibers are normally used for reinforcing the coating in more than one layer.
Polypropylene fibers are used for light duty reinforcement for the coating. They have few limitations for their utilization as reinforcement for protective coating hence they are preferred under the circumstances of budget constraints and for light duty requirements.
Execution of fiber as reinforcement for the protective coating needs to be checked with compatibility of both – fiber and the coating for their mechanical and dynamic properties. Coefficient of thermal expansion / contraction for both of them also needs to be examined with respect to the surrounding environmental conditions. One of the biggest advantages of these reinforcing materials is significant improvement in ductility of the members which are coated with these reinforced coatings.
Glass flakes are also used to reinforce the protective coating. Their shape and size is important criterion for their selection. Glass flakes generate micro layers within the coating due to which corrosive elements are restricted from entering the coating film.
Material of reinforcing the protective coating is always to be checked while selecting the same for its compatibility of coefficient of thermal expansion and contraction; the material of member on which it is being applied; desired shear strength and compressive strength.
Chirag K Baxi.
Technical Director – Prudent Forensic Consultancy Private Limited,
Honorary Director – Steuler Industrial Solutions Private Limited,
General Manager – K K Retroflex solutions.