Experimental and theoretical investigation of basalt FRP-strengthened lightweight self-compacting concrete rectangular columns

The importance of investigating the use of basalt fiber-reinforced polymers (basalt FRP) bars in lightweight self-compacting concrete (LWSCC) generally stems from its potential to offer more environmentally friendly, durable, and effective solutions for a variety of construction projects while addressing issues with conventional materials and methods. Literature shows that the use of basalt FRP along with spiral-hoops lateral strengthening in FRP-strengthened LWSCC columns has not been examined by researchers considering different formations. Therefore, the present study has endeavored to investigate the different configurations of lateral strengthening in FRP-strengthened LWSCC concrete rectangular columns including exterior basalt FRP hoops and interior basalt FRP spiral, interior and exterior basalt FRP hoops providing double restraints, and single basalt FRP hoops. Various parameters of fabricated columns are investigated including the diameter of crosswise strengthening, longitudinal strengthening material type, the vertical spacing of hoops, and different configurations of hoops. A new theoretical model is also suggested to predict the compressive load of LWSCC columns by involving the contribution of longitudinal and crosswise basalt FRP bars. The outcomes of the current investigation depicted that the use of basalt FRP along with spiral-hoops crosswise strengthening in FRP-strengthened LWSCC columns is the most efficient in terms of core restraint and compressive load compared with the other two configurations. The ductility of the samples reduced from 15.91 to 13.16 depicting a reduction of 20.89%, after lowering the pitch of hoops from 100 to 50 mm. By reducing the vertical distance between crosswise strengthening, the ductility of the columns improved with secondary peaks in the load-deflection curves. The proposed theoretical model performed well in capturing the compressive load of FRP-strengthened LWSCC columns.