Recycling of reclaimed fibers from end-of-life tires in hot mix asphalt

Nowadays, the disposal of end-of-life tires (ELT) is worldwide one of the major concerns for the environment as well as for public health. Crumb rubber and steel wires, the main by-products (in terms of weight) deriving from the ELT processing, can be recycled in several ways. However, the textile fiber, representing about 10% of the waste by weight, is typically not reused and ends up in landfills or incinerators. The present paper deals with the use of reclaimed fibers from ELT in hot mix asphalt (HMA), with the aim to improve its performance. The study included the preliminary characterization of the fiber through microscope observation and Fourier trans form infrared (FTIR) spectroscopy and then the investigation of the mechanical properties of HMA containing ELT fibers, in comparison with an ordinary HMA with no fibers. In particular, indirect tensile strength (ITS), indirect tensile stiffness modulus (ITSM), semi-circular bending (SCB), three point bending (3PB) and indirect tensile fatigue (ITF) tests were carried out. The results showed that the use of ELT fibers does not reflect in a significant improvement in terms of strength and stiffness properties. However, the ELT fibers determine a noticeable increase of the HMA resistance to fatigue, probably related to the ability of the fibers in sewing the micro-crack edges and contrasting the macro-crack opening.