Experimental Analysis And Flexural Behavior Of Reinforced Concrete Beams Reinforced With GFRP

The world today is faced with major housing and transportation crises. Steel, wood and concrete are the major economical and available construction materials. Wood is not used extensively in the tropics due to its susceptibility to termite damage. Cement is the most expensive ingredient in concrete. Minerals required to make cement are present on our earth in almost limitless quantities and are geographically widely distributed.The last two decades have seen a rapid growth in the use of high strength concrete. The use of high strength concrete permits structural elements with smaller cross-sections. Larger spans are feasible in bridges resulting from the reduced dead loads. High strength concrete is more brittle than the previously used normal strength concrete, making it a prime candidate for fiber reinforcement.The art of reinforcing clay with straw in the manufacture of bricks can be traced back to biblical times. Steel, polypropylene, glass and natural fibers continue to be tested for structural applications.Natural fibers can be cheaply extracted from a variety of plants that grow in various geographical regions. Some natural fibers have been used in non structural cement mortar composites. The dwindling material resources and meager economic resources in most of the third world, and the threat from natural disasters like earthquake effects on buildings and bridges, call for an investigation of the feasibility of using natural fibers in high strength concrete.The suitability of using a natural fiber to reinforce high strength concrete for structural purpose was investigated. The compression and tension behavior of high strength concrete reinforced with glass fibers were compared with the behavior of high strength concrete without fiber reinforcement and with high strength concrete reinforced with either steel or polypropylene fibers. Flexural behavior was investigated by comparing results from beams reinforced as follows, (1) Conventional reinforced concrete, (2) conventional reinforced concrete with glass fibers, (3) Conventional reinforced concrete with steel fibers and (4) Conventional reinforced Concrete with polypropylene fibers.Glass fibers showed an inferior performance compared to steel and polypropylene fibers when used in high strength concrete. Steel, wood and concrete are the major economical and available construction materials. Each material has unique strength and stiffness behavior which is incorporated into design. It is not uncommon to use the three materials together where each material's properties are complemented by the others as required in design.Wood is not used extensively in the tropics due to its susceptibility to termite damage. Concrete is made from sand, gravel, water and cement. Cement is the most expensive ingredient in concrete. Using cement, which can be produced for a small fraction of energy required to produce steel or plastics, will enable our resources to be stretched further. Furthermore, minerals required to make cement are present on our earth in almost limitless quantities and are geographically widely distributed. These factors have contributed to the vast usage of reinforced concrete. Concrete used in conjunction with steel forms the composite material called reinforced concrete which possesses strength, stiffness and ductility properties.Fiber-reinforced-polymers are a manufactured material that can be designed for specific characteristics required by the engineer. FRP products are common in recreational equipment, such as fishing poles, skis, water craft, and in the military, products range from helmets to fighters. However, use of FRP products in the infrastructure has been limited because of their relative cost. Recently there has been an increasing interest in the use of FRP reinforcement in bridges and improved manufacturing technology has reduced FRP production costs. As a result, these products have become an economical and advantageous alternative to steel reinforcement in corrosive environments.There is a wide variety of currently available FRP reinforcement systems, including ropes for prestressing applications, grids for slab reinforcement and rods for conventionally reinforced members. The systems are assembled from the basic FRP bars made from commercially available fibers, such as carbon, aramid and glass. The bars are formed through a pultrusion process that pulls continuous fibers through a resin bath into a forming/curing die to form a generally smooth composite rod. Glass-fiber-reinforced-polymer (GFRP) rebar is the least expensive of the three FRPs listed above and represent the most likely alternative to bridge deck reinforcement. Overall, GFRP reinforcement has significant advantages over normal steel reinforcement:high strength to weight ratio (10 to 15 times steel), excellent corrosion resistance, and excellent electromagnetic neutrality. However, the disadvantages need to be carefully considered:questionable fatigue characteristics, higher cost (five times steel), low modulus of elasticity (resulting in excessive deflections), low failure strain, long-term strength that can be lower than short-term static strength, and unknown durability in concrete due to the alkali-silica reaction. Additionally, there is a lack of manufacturing and testing standards for GFRP rebar. Its performance as a reinforcement is not sufficiently understood to warrant unconditional use in the infrastructure. Extensive research is required to understand its strengths and weaknesses. The benefit of this new material is the possible savings of billions of dollars in costly corrosion problems.The overall study plan includes (1) development of design procedures for an GFRP hybrid reinforced beams system; (2) laboratory studies of static and fatigue bond performances and ductility characteristics of the system; (3) accelerated durability tests of the hybrid system; and (4) static and fatigue tests on full-scale hybrid reinforced composite bridge decks. This paper presents the results relating to the flexural behavior of the polypropylene-fiber-reinforced-concrete beams reinforced with GFRP rebars.