Feasibility study on macro synthetic fibre reinforced concrete for sleeper applications

Abstract

With the increase in railway traffic and axle loads over the last few decades, traditional sleepers are experiencing more premature failure, resulting in significant maintenance costs. Indeed, most recent studies have revealed that sleepers made of either timber, steel or prestressed concrete are not entirely adequate for modern railway operational conditions. While concerns about sleeper materials have long been acknowledged, in practice, replacement with composite alternatives remains fairly limited. In this thesis, the implementation of macro synthetic fibre reinforced concrete (MSFRC) for railway sleeper applications is comprehensively assessed under static loading conditions. The macro synthetic fibre reinforcement adopted is the high-performance structural BarChip fibres that are typically used to increase toughness and ductility, and also eliminate durability concerns due to corrosion. Because of these encouraging benefits in the fundamental mechanical properties of concrete, a thorough experimental program is developed to evaluate the optimum fibre dosage and fibre type. Subsequently, the mix design is optimised to ensure industry compliance prior to investigating the full-scale structural performances of MSFRC sleepers subjected to positive and negative bending moments. The results achieved with the integration of macro synthetic fibres at 1.0% volume ratio was most beneficial at improving the residual capacity, cracking resistance and overall ductility of both the material and structural responses. The optimised MSFRC sleeper is shown to be a feasible design that delivers adequate structural capacity through a more sustainable reinforcement system, with the potential to provide a cost-efficient alternative for the railway industry. Using a life cycle costing approach, the long-term financial benefits of macro synthetic fibre reinforcement in sleepers are acknowledged despite their relatively high investment costs. These cost savings mainly depend on the partial elimination of prestressing wires and the extended service life provided by incorporating macro synthetic fibres, compared with the conventional sleeper materials. While the financial analysis includes a degree of variability based on the economic conditions, a sensitivity study is also conducted to demonstrate the cost-effectiveness of MSFRC over traditional sleepers at various risk levels. Based on the economic comparison, this research offers recommendations for sleeper manufacturing facilities and track owners to promote the adaptation of macro synthetic fibre reinforced concrete in railway sleepers.

Date of Award	2021
Original language	English