“Subballast project” design of a new recycled crumb rubber bituminous layer in the railway track subgrade

Bituminous subballast rail track, compared to conventional granular
subballast track not only reduces maintenance costs, but also increases subgrade bearing
capacity and impermeability. Furthermore, bituminous products are likely to be mixed with
recycled materials, which is useful to environment. Because of that, improved viscoelastic
properties can be achieved as it is provided a better vibration reduction. In addition, the main
problem of granular subballast as a track material is its low level of obtainment from quarry.
“SUBBALLAST PROJECT” pretends to take advantage from bituminous material
properties so that these kinds of products take part into the subgrade. Thus, two main
premises have been set up. On the one hand, the features of this new solution have to improve
or equalize granular subballast ones. On the other hand, the final investment has to be lower.
In this way, another condition has been established. It is pretended to find the right
bituminous dosage which is able to offer a similar structural behaviour as granular materials
Three different types of bituminous dosages have been taken into account, and their
mechanical behaviour has been established. According to this research, asphalt with crumb
rubber provides relevant advantages by the time the environment is respected as crumb
rubber particles come from outdated car tires. In order to attain the correct bituminous layer
thickness, a finite element model has been performed. Then a testing track is going to be built
so that the solution is tested in a real situation.