Effects of blast furnace slag and steel fiber on the impact resistance of railway prestressed concrete sleepers

This study aims to investigate the effects of ground granulated blast furnace slag (GGBFS) and steel fibers on the flexural behavior of railway prestressed concrete (PSC) sleepers under static and impact loads. For this, two types of railway PSC sleepers with 14 or 16 prestressing strands were fabricated, and two different hammers with weights of 400 and 500 kg dropped at a height of 2 m for providing two potential energies of 7.85 and 9.81 kJ for the impact resistance. The structural integrity of the sleepers after impact damage was examined by evaluating their residual flexural performance. Test results indicated that the addition of 0.75 vol% hooked steel fibers was effective in improving the flexural performance of the sleepers at both static and impact loads, while the inclusion of GGBFS led to an improvement in the static flexural performance only. Based on our analysis of cracking behavior, enhancements in static and impact resistance of the sleepers with steel fibers were caused by the limited formation of cracks and a decrease in maximum crack width. Higher flexural strengths of all tested sleepers were also obtained under the impact load than under the static load, and the increase was higher for higher potential energies because of the strain-rate effect. The enhanced residual capacity (i.e., higher strength and stiffness) of the PSC sleepers was obtained by including steel fibers and increasing the number of strands. In addition, slightly lower dynamic load factors were observed for the fiber-reinforced PSC sleepers than those without fibers, meaning that the sleepers with steel fibers were less sensitive to the strain-rate than their counterparts without fibers.