Serviceability performance of fiber-reinforced lightweight aggregate concrete beams with CFRP bars

Abstract

Six lightweight aggregate concrete (LWC) beams reinforced with carbon fiber–reinforced polymer (CFRP) bars were tested under a four-point bending load with different steel fiber contents, reinforcement ratios, and clear span lengths to investigate their flexural behavior and serviceability performance. The test results showed that using steel fiber–reinforced lightweight aggregate concrete (SFLWC) and increasing the reinforcement ratio enhanced the serviceability performance of the beams. The incorporation of 0.6% by volume of steel fibers reduced the midspan deflection by 22.70%–36.87% at the same load level in service stage. At service load, all the CFRP-reinforced beams exhibited conservative deflections when compared to the deflection limits recommended by ACI 440.1 R and GB 50608, and satisfied the crack width limit of 0.7 mm. Comparing the measured maximum crack widths with the corresponding predictions revealed that the bond-dependent coefficient value of 1.4 specified in ACI 440.1 R was reasonable yet conservative. Moreover, an energy-based method was adopted to quantify the influence of the fibers on the beam stiffness. On this basis, a rational deflection model for SFLWC beams reinforced with CFRP bars was suggested.