In silico simulation study on moisture- and salt water-induced degradation of asphalt concrete mixture.

The moisture- and salt water-induced degradation of asphalt concrete molecular systems was investigated via molecular dynamics simulations. To establish the microstructure-to-property relationship of asphalt concrete mixture under hygroscopic aging, water molecules and sodium chloride (NaCl) ionic solutes were uniformly distributed in the binder or concentrated at the interface. The mechanical properties of the binder were slightly degraded by moisture and NaCl solutes. The viscosity of the binder decreased with distributed water, whereas it increased as the content of NaCl solute in the salt water increased. Moreover, the NaCl solutes promoted the hygroscopic eigenstrain of the asphalt binder. The interfacial properties between the binder and aggregate were not noticeably affected when moisture and NaCl solutes were uniformly distributed in the binder. While the moisture penetration into the interface was thermodynamically spontaneous when the amount of water was sufficient, the NaCl solutes in the water hindered the diffusion of moisture into the interface. Nonetheless, salt water penetrated into the interface seriously reduced the interfacial adhesion and the cohesive law in mode I and mode II decohesion than pure water. The condensation of penetrated salt water and the associated peeling mechanism of the interface were discussed to clarify the hygroelastic damage mechanism of the asphalt concrete mixture. • Degradation of hygroscopically aged asphalt concrete mixture was studied. • Moisture and Salt water resulted in hygroscopic swelling and remarkable change in viscosity of AAA-1 binder. • Penetration of water molecules in asphalt mixture was thermodynamically spontaneous and degraded the interface. • Dissolved NaCl mitigated the penetration of salt water while seriously deteriorated the interface in asphalt mixture. • Hygroelastic properties of binder and interface essential to constitutive modelling of asphalt mixture were determined. [ABSTRACT FROM AUTHOR]