Experimental and Theoretical Study on the Flexural Behavior of Recycled Concrete Beams Reinforced with GFRP Bars

Abstract

This paper experimentally investigated the flexural behavior of reinforced recycled aggregate concrete (RAC) beams reinforced with glass fiber-reinforced polymer (GFRP) bars. A total of twelve beams were built and tested up to failure under four-point bending. The main parameters were reinforcement ratio (0.38%, 0.60%, and 1.17%), recycled aggregate replacement ratio (R = 0, 50%, and 100%) and longitudinal reinforcement types (GFRP and steel). The flexural capacity, failure modes, flexibility deformation, reinforcement strains and crack distribution of the tested beams were investigated and compared with the calculation models of American code ACI 440.1-R-15, Canadian code CSA S806-12 and ISIS-M03-07. The tested results indicated that the reinforcement ratio has great influence on the ultimate load, crack width and deflection of GFRP-RAC beams, the recycled aggregate replacement ratio has little influence on it. However, it was found that the reinforcement ratio has no obvious influence on the cracking load which was only related to the recycled aggregate replacement ratio. The average cracking load decreased by 5% and 15% as the recycled aggregate replacement ratio increased from 0 to 50% and 100%. For the steel-RAC beams, the ultimate load was found to be about 1/2 of the ultimate load of GFRP-RAC beam under the same condition and the trend of strain, deflection and crack width were different from GFRP-RAC beams. This is due to the different material properties of GFRP bars and steel rebar. On the other hand, the calculation results showed that ACI 440.1-R-15 and CSA S806-12 underestimated the ultimate load of GFRP-RAC beams. Moreover, the deflection prediction of GFRP-RAC beams by CSA S806-12 is relatively accurate compared with ACI 440.1-R-15 and ISIS-M03-07. As for the prediction of crack width, the results of ACI 440.1-R-15 prediction were in good agreement with the experimental results at the ultimate load, with the average value of 1.09 ± 0.28.