Behavior and Strength of Steel-Carbon-Plastic Hybrid Fiber Reinforced Concrete Beams

Abstract

Fibers like steel, carbon, plastic; polyester, jute, etc. are add up to concrete known as fiber reinforced concrete. To obviate the deficiencies of concrete, fibers are added to concrete to reform the behavior of concrete. The fibers serve as not only the cracking control reinforcement, but also the vehicle to allow for significant internal plastic stress redistribution to increase the strength of the specimens after the first crack forms[1]. In this study hybrid reinforced concrete is made by adding steel, carbon and plastic fibers. (Steel + carbon and plastic + carbon) are used in order to combine the advantages of all of them and to make the mixture more economical by substituting half of the addition of carbon fiber with steel fiber and plastic fiber which cheaper carbon fiber; Addendum of steel fibers can increase compressive, tensile, and flexural strengths of concretes along with the post-cracking ductility while plastic fibers increase the resistance of concrete to cracking. Six beams were molded and tested over an effective span length 1000 mm up to failure under two concentrated loads. One beam molded without any strengthen (as a reference beam). Three beams were strengthened with three types of fibers (carbon fiber, steel fiber and plastic fiber) and 0.2% volume fraction. While the two last beams were strengthened with hybrid fibers(carbon fiber + steel fiber and carbon fiber + plastic fiber) (0.1% + 0.1%) for each fiber. Estimation of load –deflection response to the six beams. The results show a good amelioration provided after using of fibers as matched with the reference beam (without fiber). The results also show that using of hybrid fiber lead to a good improvement in the ultimate load value [increased (Pu) by 58.5% for (S.F + C.F) and by 38.5% for (P.F + C.F), while when use only (S.F) alone ultimate load increased (Pu) by 55.4% and for (P.F) alone ultimate load increased (Pu) by 6.62%.