BITUMEN STABILIZED BALLAST: A FULL-SCALE INVESTIGATION ON ITS USE FOR EXISTING AND NEWLY CONSTRUCTED RAILWAY TRACKBEDS

Despite its worldwide spread, traditional ballasted track still presents considerable problems of settlement and particle degradation, which lead to high maintenance costs and low durability. In this regard, in recent years, to mitigate these issues mainly related to the unbound nature of ballast, several solutions have been proposed to reinforce or stabilize aggregate by means of polymers or resins. In this context, the use of bitumen stabilized ballast (BSB) has been recently proposed as relatively economic solution to extend ballast service life with an easy to apply (maintenance) practice. The aim of this study was to analyze the viability and effectiveness of using BSB in order to reduce the need for maintenance associated with ballast settlement and degradation. For this purpose, a two stages methodology was completed. The first part focused on the influence of bitumen emulsion properties on stabilization method and on selection of most desirable design parameters to pass on a full-scale investigation aimed at testing BSB effectiveness on trackbed mechanical performance and durability when applied at both track construction and maintenance level. Results showed that the bitumen emulsion properties play an essential role on stabilization method (higher viscosity and faster setting BE being more appropriate) obtaining lower settlement than conventional ballast while its stiffness and damping capacity are modified, which could be appropriate for the optimization of track behavior. In addition, this technology was able to reduce stress transmitted to sub-layers as well as particle degradation, suggesting the potential for a more durable trackbed.