Influence of low-temperature physical hardening on stiffness and tensile strength of asphalt concrete and stone mastic asphalt

• Stiffness of asphalt mixes increased after isothermal storage at low temperature.
• No changes of tensile strength after isothermal storage were noted.
• Physical hardening of asphalt concrete and stone mastic asphalt was different.
• Two measures of physical hardening of asphalt mixes were proposed.

This paper presents laboratory testing of stiffness modulus and indirect tensile strength of three asphalt concrete (AC) and three stone mastic asphalt (SMA) mixes after isothermal storage at temperature of −20 °C, at different time intervals up to 16 days. The tests under repeated dynamic loading showed physical hardening of all tested mixes which was manifested by an evident increase of their stiffness moduli after isothermal storage. Contrary to expectations, the tests on all mixes did not show any evident changes of the indirect tensile strengths which after isothermal storage remained almost constant, within normal scatter range. The differences in the physical hardening of asphalt concrete AC and stone mastic asphalt SMA were found. At the beginning of isothermal storage at −20 °C the physical hardening was slower for the SMA. After 5–16 days of storage the SMA showed greater physical hardening than the asphalt concrete AC. Two measures which allowed the quantification of intensity of the physical hardening were introduced.