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Civil-Comp Proceedings
ISSN 1759-3433
CCP: 110
Edited by: J. Pombo
Paper 24

Unbound Granular Materials for Sub-Ballast Layers and their Mixing with Rubber Particles from Scrap Tyres

C. Hidalgo Signes1, P. Martínez Fernández2, M.E. Garrido de la Torre1 and R. Insa Franco2

1Department of Geotechnical and Geological Engineering, Universidad Politécnica de Valencia, Spain
2Department of Transport Engineering and Infrastructure, Universidad Politécnica de Valencia, Spain

Full Bibliographic Reference for this paper
C. Hidalgo Signes, P. Martínez Fernández, M.E. Garrido de la Torre, R. Insa Franco, "Unbound Granular Materials for Sub-Ballast Layers and their Mixing with Rubber Particles from Scrap Tyres", in J. Pombo, (Editor), "Proceedings of the Third International Conference on Railway Technology: Research, Development and Maintenance", Civil-Comp Press, Stirlingshire, UK, Paper 24, 2016. doi:10.4203/ccp.110.24
Keywords: railways, scrap tyres, waste tyres, unbound granular material, subballast, bearing capacity, degradation.

Nowadays scrap tyres pose a significant environmental threat. Reusing them as a raw construction material is one of the most promising alternatives for their disposal. Within this context, the present paper proposes reusing scrap tyres in the form of unbound aggregate-rubber mixtures to be used as a subballast layer. This option offers two potential advantages. On the one hand, it allows the reuse of large quantities of this problematic waste material. On the other hand, in Eastern Spain most aggregates are supplied from quarries located in calcareous formations. These materials usually present a high degree of fragmentation and are not particularly resistant to degradation.

The main objective of the project, described in this paper, is to characterise rubber-aggregate mixtures in order to assess their reliability as a substitute for traditional subballast. Therefore, aggregates from five different quarries located in Eastern Spain have been sampled and tested according to the requirements fixed by the PF-7, including the Los Angeles and Micro-Deval tests as well as permeability tests. Afterwards, mixes were prepared with varying percentages of rubber content, namely 2.5, 5 and 10 percent in terms of weight. These mixes were tested, and the results show that an addition of about 7.5 percent provides a lighter material with enhanced resistance to degradation and fragmentation.

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