Development and Implementation of Innovative and Sustainable Technologies for the Use of Scrap Tyre Rubber in Road Pavements

PROJECT DESCRIPTION

BACKGROUND

Europe produces an estimated 250 million used rubber tyres annually. Moreover, this number is expected to increase with an increase in vehicle fleet numbers and reduced numbers of reconditioned tyres. Historically the majority of end-of-use tyres were sent to landfill sites. However, the landfilling of whole tyres – which creates significant environmental problems – has been banned since July 2006, under the EU Landfill Directive (1999/31/CE). Moreover, the revised EU End-of-Life Vehicles Directive (2011/37/EU) now requires the reuse and/or recovery of almost all used tyres. One alternative that has been widely investigated and reported upon by scientists worldwide is the reuse of scrap rubber tyres as a material in the construction of pavements. Previous experiences in Europe and the US have validated a so-called ‘wet’ technology, based on the use of finely ground tyre rubber (with maximum particle size smaller than 0.8 mm) that is added to the binding phase of bituminous mixtures used in pavement materials. This technology has been successfully implemented with the development of appropriate standards for the design and laying of special bituminous mixtures which, depending on their composition and on their corresponding functional and structural properties, are referred to as ‘gap-graded’ or ‘open-graded”. Recent trials carried out by the Province of Turin and the Turin polytechnic (Politecnico di Torino) have examined the use of such gap-graded mixtures for the maintenance of pavements of the local road network.

OBJECTIVES

The TyRec4LIFE project’s overall objective is to expand the use of bituminous materials containing used tyre rubber for pavements, focusing on issues that are currently limiting their widespread use. It will validate the use of ‘open-graded’ and ‘controlled texture’ bituminous mixtures.

Specific goals include:

The development of solutions for the reduction of energy consumption and emissions i.e. the project will consider the use of special viscosity-reduction additives (paraffins, zeolites, etc) for the reduction of mixing temperatures of bituminous mixtures containing used tyre rubber. This will also enable maintenance and construction operations to be carried out more efficiently and in more demanding environmental conditions;

Conducting trials for the preliminary implementation of the ‘dry’ technology, whereby coarser used tyre rubber is used in bituminous mixtures as a partial substitute for fine aggregates. This goal is of particular interest since this application requires much greater quantities of used tyre rubber than in the ‘wet’ process, thus providing an ideal end-use for these materials.

Expected results:

Updated standards for the construction of gap-graded bituminous mixtures with a particular emphasis on working with reduced temperature and with recycled aggregates deriving from industrial processes;

Innovative standards for the construction of ‘controlled-texture’ mixtures with a particular emphasis on creating a balance between structural and functional properties;

An innovative mixing technology for the implementation of the ‘dry’ technology;

A complete environmental assessment of the proposed technologies, with the inclusion of risk assessment concepts in the traditional lifecycle analysis;

A complete financial and economic assessment of the proposed technologies in the context of local and urban road networks;

A public database of the experimental results on various types of aggregates, scrap tyre rubber products and bituminous mixtures; and

A public database of field data from the pilot-scale and full-scale field trials.