Structural performance of reinforced self-compacting lightweight concrete beams with pozzolana aggregates under elevated temperatures

Self-compacting lightweight concrete (SCLWC) incorporating natural pozzolana aggregates has attracted increasing attention as a sustainable material due to its reduced self-weight, enhanced workability, and potential resistance to elevated temperatures. However, the combined influence of thermal exposure and reinforcement configuration on both the flexural and shear performance of pozzolana-based SCLWC beams remains insufficiently investigated, representing the primary motivation and novelty of the present study, and distinguishing it from prior related studies that examined the flexural or shear behavior of pozzolana lightweight concrete beams separately, thereby contributing new experimental evidence to the existing body of knowledge on lightweight and self-compacting concrete. This study experimentally investigated the flexural and shear behavior of reinforced normal-weight concrete (NWC) and SCLWC beams under ambient conditions and after exposure to 600°C. A total of eighteen beams were tested to evaluate the influence of concrete type, longitudinal reinforcement ratio, shear reinforcement ratio, and thermal exposure on ultimate load, displacement capacity, stiffness, ductility, and failure characteristics. The results showed that replacing conventional aggregate with natural pozzolana lightweight aggregate reduced concrete density by 24.2%, while the corresponding reduction in ultimate load generally remained below 10% for most specimens. Furthermore, SCLWC beams exhibited greater deformation capacity than the corresponding NWC beams. Exposure to 600°C resulted in moderate reductions in ultimate load ranging from 3% to 19%, whereas stiffness degradation was considerably more pronounced, reaching 49% in some specimens. Despite thermal exposure, the tested SCLWC beams retained satisfactory structural performance and load-carrying capacity. Overall, the findings demonstrate that natural pozzolana-based SCLWC provides a favorable balance between weight reduction, structural efficiency, and post-fire resistance, confirming its suitability for structural applications such as multi-story buildings, bridge decks, and precast elements, where weight reduction and fire resistance are important design considerations.