Flexural Behaviors of ECC and Concrete/ECC Composite Beams Reinforced with Basalt Fiber-Reinforced Polymer

The use of fiber-reinforced polymer (FRP) reinforcement in structural engineering has attracted great attention due to high tensile strength, good fatigue performance, and inherent corrosion resistance. Engineered cementitious composite (ECC) is a class of high-performance cementitious composites with pseudo-strain-hardening behavior and excellent crack control. Substitution of concrete with ECC can avoid the cracking and durability problems associated with brittleness of concrete. In this paper, six FRP-reinforced ECC, or ECC/concrete composite beams with various longitudinal and transverse reinforcement ratios and ECC thicknesses, are tested in bending. According to the test results, FRP-reinforced ECC beams show much better flexural properties in terms of load-carrying capacity, shear resistance, ductility, and damage tolerance compared with FRP-reinforced concrete beams. For the FRP-reinforced ECC beam without stirrups, final failure occurs in shear. However, the ultimate load capacity and deformation are comparable to the FRP-reinforced concrete beams with properly designed stirrups, and the failure process is ductile due to the strain hardening behavior of ECC materials. For ECC/concrete composite beams, strategic application of ECC can lead to considerable increase of energy dissipation capacity. When a layer of ECC is placed in the tension zone, the crack width along the beam can be well controlled. High residual strength and stiffness of the composite beam can hence be obtained. In addition to experimental work, a theoretical model is proposed to predict the moment-curvature responses of FRP-reinforced ECC beams. Model results are found to be in good agreement with test data. Theoretical analysis is then conducted to illustrate the effect of reinforcement ratio, compressive strength, and thickness of ECC on the ultimate moment, curvature and ductility of beams.