Test and theoretical investigation of fiber-reinforced phosphogypsum short columns with steel- fiber composite bars (SFCB) and BFRP ties under axial compressive load

• Through seven experimental components, the influence of parameters such as fiber addition, SFCB configuration, stirrup spacing, and the number of longitudinal bars on the compression behavior of phosphogypsum short columns is systematically investigated. • The PVA fiber-reinforced phosphogypsum short column with SFCB as the longitudinal reinforcement and BFRP bars as the stirrups under axial compression load is increased by 217.62% to 275.10% compared to that of the phosphogypsum short column. • A modified formula for calculating the yield bearing capacity is proposed, which can accurately predict the yield bearing capacity of this type of component. The high brittleness and corrosiveness of phosphogypsum materials limit the structural application of such materials. To address this, PVA fibers and steel-FRP composite bars (SFCB) are synergistically employed to reinforce plain phosphogypsum short columns, aiming to enhance both their bearing capacity and ductility. This study systematically investigates the effects of key factors including PVA fiber content, SFCB configuration, BFRP stirrup spacing and the number of longitudinal bars on the compressive behavior of such columns through laboratory tests. Test results show that phosphogypsum columns reinforced with SFCB exhibit a substantial capacity increase of 144.56%, yet they remain susceptible to spalling and possess inadequate ductility. In contrast, the specimens with both SFCB reinforcement and PVA fiber exhibited the highest bearing capacity enhancement, reaching 275.10%, accompanied by the absence of noticeable phosphogypsum spalling, underscoring excellent overall structural integrity. The results show that PVA fibers can effectively inhibit the cracking in phosphogypsum, thereby enhancing the integrity of test specimens, while SFCB significantly increases their bearing capacity. To further support practical applications, a modified theoretical model and calculation formula were proposed to predict the load-stress relationship and load bearing capacity of the PVA fiber-reinforced phosphogypsum short columns with steel-basalt fiber composite bars columns. Comparative analysis reveals that this formula exhibits high accuracy when validated against test results.