Page 7 - Research and innovation un materials applied to railways

The use of these recycled materials and the search for ecodesign solutions, capable of
improving the environmental performance of materials and products through the
incorporation of recycled plastic materials instead of raw materials, is becoming a general
trend. Often the construction of infrastructures, not only railways, is faced with a problem
of scarcity of materials, either due to environmental issues or the lack of availability of the
material in the required location. The solution of treating and stabilizing floors with lime,
cement or polymer can be costly which calls for a search for other more innovative and
competitive stabilizing materials, such as pozzolan material originating from residue
1
(CDW , slag, ash, glass,…) or wastewater residues, which contain lots of heavy metals; or
natural organic materials (micro-binding bacteria). The advantage of using recycled
materials extends, for example, to sleepers developed with thermoplastic waste, which are
otherwise hard to value.

Tracks set on concrete slabs, increasingly common especially in high speed and the urban
environment (trams), have traditionally been run on concrete, which reduces
maintenance costs and improves reliability. Currently, there are developments that are
helping to overcome issues associated with excessive rigidity and therefore noise and
vibrations. These developments are based on the use of bituminous mixes modified with
rubber powder derived from out of service tyres, which provide additional shock
absorption to reduce transmission.

The growing demand in use also has an impact on the actual tracks whose service
provision is being improved. The development of new pearlite, bainite and austenite
steels, the application of surface treatments that increase the hardness and resistance of
running surfaces, contribute to increasing the service life of the rail tracks.

Rails made from pearlite steel offer in general the greatest properties, whilst severe
service conditions, with heightened deformation in the head of rail, a strong abrasion, are
driving forward the development of new rails with improved properties (fracture
toughness, fatigue, slow crack growth and wear resistance). These new steels are based on
thermal treatments, over all the rail and head of rail, in such a way that the pearlite
structure obtained presents a finer microstructure, with less interlayer distance; or in the
use of microalloyed steel with small quantities of niobium, vanadium and chromium. The
objective of these microstructure developments is to gain a material of extreme toughness
but at the same time maintaining the contact fatigue.

Other developments, in addition to mechanical properties and durability, focus on the
optimization of soldering processes (products which are becoming progressively longer)
or the control of the entire manufacturing process, through the use of visual inspection
technologies through laser (3D reconstruction) for the detection of surface defects of
products at high temperatures.

The reduction of noise and vibrations, as well as the elastic properties of structure and
sub-structure components, require the development of new solutions in the form of
lighter and less costly materials that can be used, for example, in new acoustic barrier
applications that are also harmonious with the environment and landscape.

Noise minimisation can also be addressed through the development of new materials
applied to the rail tracks. For example, the OVERRAIL project, financed under the national
RETOS programme from the Spanish Ministry of Economy and Competitiveness, seeks the

1 Construction and demolition waste (translator note).

Position Paper: Research and innovation in materials applied to railways 6