Investigation of microscopic air void structure of anti-freezing asphalt pavement with X-ray CT and MIP

The dissolution of snowmelt agent Mafilon (MFL) causes complicated modifications in the pore structure of anti-freezing asphalt mixtures. In this research, X-ray computed tomography (X-ray CT) and mercury intrusion porosimetry (MIP) were employed to study the effects of salt content, soaking time and freeze-thaw cycle on the pore characteristics. The results indicate that the air void content increases dramatically with the salt content, water bath time and freeze-thaw cycles. The loss of MFL alters gradually from the capillary action to dissolution action. The totality of pores was increased by 35.5% after four freeze-thaw cycles and the increase most concentrated in the mesopores (0.2-0.6 mm). The freeze-thaw action increases the size and number of pores, leading to the accelerated dissolution of MFL, while the modification of pores and dissolution of MFL in turn intensify the freeze-thaw damage.