Influence of Freeze–Thaw Cycles on the Mechanical Properties of Highly Rubberised Asphalt Mixtures Made with Warm and Cold Asphalt Binders

Abstract

The present study has been developed to investigate the effect of freeze and thaw (F–T) cycles on the characteristics of highly rubberised asphalt materials to be used as impact-absorbing pavement (IAP) in urban road infrastructures. The tested samples were produced in the laboratory following the dry process incorporation. Two main types of crumb rubber particles in the range of 0–4 mm were used. Moreover, two types of binders, one warm and one cold, were utilised to prove the feasibility of cold-produced admixtures. The temperature range of the F–T procedure was comprised between −18 ± 2 °C (dry freezing), and 4 ± 2 °C (in water), and the cycles were repeated, on the samples, 10 times. At 0, 1, 5, and 10 cycles, the samples were tested with non-destructive and destructive testing methods, including air voids content, ITSM, ITS, and Cantabro loss. The waters of the thawing period were collected, and the pH, electric conductivity, and particle loss were measured. A consequent change in mechanical behaviour has been recorded between warm and cold produced samples. However, the tests found that the F–T cycles had limited influence on the deterioration of the highly rubberised samples. The loss of particles in the thaw waters were identified as being potentially caused by the temperature stresses. The research suggested various ways to optimise the material to enhance the cold-produced layer mechanical performances, aiming at a fume and smell-free industrialised solution and reducing the potential leaching and particle losses.

Mechanical and leaching characterisation of impact-absorbing rubberised asphalts for urban pavements

“…Preliminary studies have confirmed the feasibility and potential effectiveness of the impact-absorbing pavements (IAP) starting from various mix designs, using both warm [8,[10][11][12] and cold bituminous binders [13]; during their development process, a complete mechanical analysis of the material was required to assess their attenuation properties. The uniaxial compression test in different setups has usually been adopted to investigate the basic loading and relaxation behaviour of these materials [6,7] because the methods commonly used for traditional asphalt, like the ITSM test (EN 12697-26), are not able to describe the considerable soft behaviour of the samples.…”