An experimental study of the insulation performance of ballastless track slabs reinforced by new fiber composite bars

Due to inductive impedance caused by steel meshes in traditional reinforced ballastless track slabs, the electric properties, primarily rail resistance and inductance, of the track circuit are affected by electromagnetic induction between the slabs and the electric current in the rail. This problem results in poor transmission performance through the track circuit. Insulating heat-shrinkable sleeves between the steel meshes have been used to improve the insulation capability of steel meshes in slabs; however, they reduce the bonding performance between the steel bars and concrete. Because of the highly insulating properties of fiber reinforced polymer (FRP) and steel-fiber reinforced polymer composite bar (SFCB), these composite materials have shown promise to overcome the insulation problem. In the study reported in this paper, single and double layer meshes and ballastless track slabs were manufactured and tested for the first time. In the research reported herein, basalt fiber reinforced polymer (BFRP) and SFCB were used in meshes and slabs, respectively. The electric properties of the rail affected by these meshes and slabs were investigated and compared with steel meshes and ordinary reinforced ballastless track slabs (RC). As the test results demonstrated, the signal frequency and distance between the slabs or meshes and the rail had a significant impact on the electric properties of the rail. Furthermore, the variation in rail resistance induced by the slabs or meshes increased drastically, while the change in rail inductance increment varied slowly. BFRP and SFCB used as transverse reinforcement of slabs or meshes reduced the variation in the electric properties of the rail. BFRP reinforced ballastless track slabs had the highest insulating performance, while those with SFCB demonstrated the second highest performance.