Advanced hybrid nonmetallic composite reinforcement for concrete structures

Abstract

During the last decades, fiber reinforced polymer (FRP) reinforcing bars for concrete structure has been extensively investigated and a number of FRP bars became commercially available. However, major shortcomings of the existing FRP bars are its low elastic modulus and high initial cost compared to conventional steel bars. The possibility to obtain a hybrid composite reinforcement (HCR) with increased performance based on glass and carbon fibers (GCFRP) is considered. The optimal content of carbon fibers in the amount of 6.3 − 6.5 % of the mass of the HCR was established. Further increase in the carbon fiber content gives a slight improvement in physical and technical characteristics, which is not comparable to the increase in the cost of the material. The manufacturing technology of HCR has been developed. The effect of hybridization on tensile properties of FRP bars were obtained by comparing the results of tensile test with those of non-hybrid GFRP bars. Operation regularities of HCR in the bent concrete beams are established. HCR can increase the stiffness of concrete beams by 15 % and crack resistance by 12 % in comparison with glass composite reinforcement. Dependences for predicting the HCR elasticity modulus are established. Physical and technical characteristics of HCR, including adhesion to concrete and resistance to the alkaline medium, were established. High durability of HCR for more than 50 years is experimentally shown. Experimental-industrial concrete piles, reinforced with GCFRP bars were produced and tested. For further development, new types of HCR, as well as a study of prestressed concrete structures are recommended.