Influence of Physical Hardening on the Low-Temperature Properties of Bitumen and Asphalt Mixtures

A laboratory study was carried on the effects of physical hardening on the low-temperature performance of bitumen and corresponding asphalt mixtures. Bitumen testing involved measurements of glass transition temperature and creep stiffness at various isothermal storage times. Mixture testing included evaluation of glass transition temperature, thermal stress build-up in restrained conditions and thermal strains in non-restrained conditions. A physical hardening rate was introduced both for bitumen and mixtures (PHRB and PHRM). Results indicated that glass transition temperatures can be reduced passing from bitumen to mixtures and a correlation can be found between the hardening rates PHRB and PHRM.