i know that there are some differences between each of steel, glass, and polypropylene fibers. but is there any disadvantages of using them in repairing of concrete members. who is the best type of them?
Dear Ahmed ,,hope this article interested for you.......
Different Types of Fibers Used for Concrete Reinforcement
Natural fiber reinforced concrete (NFRC) consists of cellulose fibers that are processed from pine trees. This category is also producing good results. The recycled carpet waste has been successfully used for concrete reinforcement by using the waste carpet fibers.
Polypropylene Fiber Reinforced (PFR) concrete: Polypropylene is a cheap and abundant polymer widely used due to its resistance to forming chemical reactions.
Asbestos Fibers: These fibers are cheap and provide the cement with mechanical, chemical and thermal resistance, although the asbestos fiber reinforced concrete appears to have low impact strength.
Carbon Fibers: These fibers have been recently used due to their very high modulus of elasticity and flexural strength. Characteristics such as strength and stiffness are better than those of steel fibers, although they are more susceptible to damage.
Steel fiber reinforced concrete is a composite material that can be sprayed. It consists of hydraulic cements with steel fibers that are dispersed randomly and possess a rectangular cross-section. The steel fibers reinforce concrete by withstanding tensile cracking. The flexural strength of fiber reinforced concrete is greater than the un-reinforced concrete. Reinforcement of concrete by steel fibers is isotropic in nature that improves the resistance to fracture, disintegration, and fatigue. Steel fiber reinforced concrete is able to withstand light and heavy loads.
Every fiber type has its own advantages as well as disadvantages depending upon what type of load the member under repair is supposed to carry. In the area of maximum deflection in flexure, the fibers of higher modulus of elasticity like glass, polymers and carbon fibers are to be preferred. While for failures due to shear, steel fibers will be advantageous.
Fiber types mentioned above are very different taking into account main criteria: strength, ultimate strain, corrosion resistance, technological, ecological, special (functional) properties and, of course, cost of material. Particularly, steel fibers are preferable for the filling of concrete which is used for the electromagnetic radiaton protection. In some cases, we may combine the advantages of different fibers by their mixing (so-called hybrid fiiling).
Fibers are utilized in cement to manage the cracking characteristics and reduce permeability. The surrounding concrete protects the steel used for reinforcement. Glass fiber reinforced concrete is used for architectural products and steel fibers are mostly used for paving and inside tunnels.
You can find further details on the given link.
http://www.brighthubengineering.com/concrete-technology/47714-types-of-reinforced-concrete/
Yes as he fibers are different categories they have different properties like E, tensile strength, elongation etc. For the repairing purpose PP or Glass fiber is a good selection as compare to steel fiber. As steel fiber is a corrosion material. PP cost is also less as compared to Glass fiber and steel fiber. old RCC beam can be repair by using retrofitting techniques.
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