Decarbonization of the concrete railway sleeper production: bringing the low-dosage pozzolanic cement usage in the sleeper production via novel laminated CFRPU reinforcement technique

This study presents four new concrete railway sleeper models' environmental emission and service life investigations. Both of these two factors are crucial for a sustainable railway sleeper model. Investigated sleepers are solely reinforced with engineered laminated carbon-fiber-reinforced polyurethane (L-CFRPU) materials. This novel concrete sleeper reinforcement technique was needed to overcome the following two challenges preferred because of the environmental sustainability objectives: First, the new LCR-G-type sleepers are produced with a 30% lower (on average) cement dosage. Second, an eco-friendly cement containing approximately 50% natural pozzolan is utilized. Accordingly, the new sleeper model's total concrete raw materials-based equivalent CO2 emission value is 54% less (on average) than conventional concrete railway sleepers. This emission decrease (decarbonization) rate is well above the other eco-friendly concrete sleeper studies in the literature. However, the compressive strength of the sleeper concrete has almost halved. For this reason, investigations continued with the mechanical strength tests specified in the concrete sleeper standards for preliminary service life evaluations. For these purposes, in this study, the latest EN 13230-3:2016 standard test setup was used with some improvements, such as precise deflection measurements oriented to the sleeper-rail-seat- center points. The test results show that all four models of new LCR-G-type sleeper variations have met the sleeper technical specifications' static strength limits and crack-reclosing conditions. Consequently, it is recommended to investigate further the sustainability potential of this new concrete sleeper production method, whose preliminary evaluations have been made in this study for the first time in the literature