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

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.

Automated summary

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. At service load, all the CFRP-reinforced beams exhibited conservative deflections and satisfied the crack width limit. Moreover, an energy-based method was adopted to quantify the influence of the fibers on the beam stiffness, leading to a rational deflection model for SFLWC beams reinforced with CFRP bars.