Experimental study on transfer length of an eco-friendly prestressed concrete sleeper

• An eco-friendly PC sleeper was developed by using GGBF slag and EAF oxidizing slag.
• CO2 emissions and the usage of natural were reduced.
• The transfer lengths in the eco-friendly concrete sleeper were measured.
• The transfer lengths of the eco-friendly concrete sleeper were significantly improved.
• The long-term effects of the eco-friendly concrete were relatively insignificant.

This study focuses on investigating transfer length in a newly developed eco-friendly concrete prestressed concrete sleeper. A next generation prestressed concrete sleeper was developed at the Korea Rail Research Institute (KRRI) in order to improve structural performances of the current prestressed concrete sleepers while addressing some environmental issues such as CO2 emissions and a lack of natural resources. The authors used ground granulated blast furnace (GGBF) slag and electric arc furnace (EAF) oxidizing slag to reduce the amount of Portland cement (III) and natural sand. To ensure the safety and structural integrity of the newly developed sleeper prior to a mass production and installation in the field, the structural performances of this newly developed eco-friendly concrete sleeper ought to be studied. One of important structural performances of prestressed concrete members which should be measured is transfer length. Unlike other civil engineering fields, no design guidelines for transfer length in prestressed concrete sleepers have been established in the railway industry. For example, the American Concrete Institute Building Code and the American Association of State Highway and Transportation Officials Bridge Design Specifications specify the required transfer length in prestressed concrete beams or girders depending on the size of prestressing wires or strands. Therefore, this study examines transfer length in the newly developed eco-friendly concrete sleeper and compares that with the transfer length in traditional prestressed concrete sleepers. Four sleepers are manufactured for each concrete, and the transfer length in each sleeper is monitored at the day of prestress release, and 7, 28 and 90 days. As monitoring the behavior of the sleepers over 90 days, the long-term effect on the transfer length is also investigated. The study demonstrates that the transfer length in the eco-friendly concrete sleepers is not only shorter than that of the traditional prestressed concrete sleepers, but also found to be more desirable since the prestress is fully developed prior to the railseat area.