Lightweight concrete (LWC) offers significant advantages in reducing self-weight of structures; however, its porous aggregates and weak aggregate-matrix interfaces reduce strength and limit confinement efficiency under multiaxial stress states. This study experimentally investigates the synergistic effects of steel fiber reinforcement and lateral confinement on the triaxial compressive behavior of structural-grade LWC. Cylindrical specimens reinforced with 0.5%, 1.0%, and 1.5% hooked steel fibers were tested under confinement pressures of 5 and 10 MPa. Results show that lateral confinement and steel fibers jointly enhance strength and deformation capacity by altering failure mechanisms: steel fibers bridge microcracks and delay tensile splitting, while confinement suppresses lateral dilation and promotes shear-dominated crushing. Under 10 MPa confinement, compressive strength increased from 33.1 MPa for plain LWC to 54.5 MPa for specimens with 1.5% fibers. Mohr-Coulomb analysis demonstrates a substantial increase in confinement efficiency, with the confinement coefficient K rising from 1.8 for LWC to 3.37 for fiber-reinforced LWC, approaching values reported for normal-weight concrete. The findings demonstrate that appropriate combinations of fiber volume (1-1.5%) and confinement pressure can mitigate the inherent weaknesses of LWC, providing quantitative parameters for the design of confined LWC columns, seismic elements, and lightweight modular structural systems.
Sorkohi et al. (Wed,) studied this question.