Development and performance evaluation of self-healing concrete railway sleepers using different size PU tubes

The rail seats and middle are the main critical zones in railway concrete sleepers wherein the damage normally occurs due to high positive and negative bending moments, respectively. To address this issue, self-healing concrete railway sleepers (SHCRS) were developed by reinforcing the sleepers with polyurethane (PU) filled glass tubes, and their bending performance was subsequently investigated. A total of sixteen full-scale reinforced concrete railway sleepers with different diameters of glass tubes (4 mm and 9 mm) and lengths (50 mm and 200 mm) were manufactured and tested under three-point bending at the rail seat up to 440 kN for intact and 220 for damaged sleepers, as well as in the middle of the sleepers at 160 kN for intact and 70 kN for damaged sleepers. The digital image correlation (DIC) method was used to study the fracture behavior of SHCRSs, eval-uating the crack strains and crack width openings, and their behavior was compared with conventional rein-forced concrete sleepers. Short tube sleepers perform better in the rail seat where they have a further distance the maximum flexural zone than the middle does, almost 60 mm. Meanwhile, long tube sleepers have a better performance in the middle of the sleeper, with a distance of 40 mm from the maximum flexural zone due to the greater slenderness of long tubes as opposed to short tubes. A FE model was developed to measure different slenderness ratios for long and short tube sleepers. The results show that the slenderness ratio and surface area volume ratios (sa/vol) of the PU tubes have a significant effect on the healing of damaged sleepers. Decreasing the slenderness ratio from 250 to 200 on the short tubes increases the applied stress by 11 % in the rail seat and 450 % in the middle of the sleeper.