A fracture-based approach to characterize long-term performance of asphalt mixes under moisture and freeze-thaw conditions

• Published in: Engineering fracture mechanics Vol. 241; p. 107418
• Main Authors: Karimi, Mohammad M., Dehaghi, Ehsan Ahmadi, Behnood, Ali
• Format: Journal Article
• Language: English
• Published: New York Elsevier Ltd 01-01-2021; Elsevier BV
• Subjects: Asphalt mix; Asphalt mixes; Asphalt pavements; Cracking (fracturing); Damage detection; Fracture resistance; Fracture toughness; Freeze thaw cycles; Freeze-thaw damage; Freeze-thaw durability; Impact damage; Moisture; Moisture damage; Properties (attributes); Semi-circular bending; Service life; Strain energy release rate; Stress intensity factors; Testing; Semi-circular bending; Moisture damage; Freeze-thaw damage; Fracture resistance; Asphalt mix
• ISSN: 0013-7944; 1873-7315
• DOI: 10.1016/j.engfracmech.2020.107418

Case I:
The asphalt mix experiences damages due to traffic loading and environmental conditions. In a mild climate region, the main reason for damages is the repeated traffic loading, and the environmental conditions have minor effects on the reduction of pavement serviceability.
Case II:
In harsh climate regions (e.g., cold and tropical), moisture and freeze-thaw damages intensify damages caused by the traffic loading. In this case, the final serviceability of pavement is much lower than that in mild climate regions (Case I). Therefore, a comprehensive and precise approach is required to assess the long-term fracture resistance of asphalt mixtures under moisture and freeze-thaw damages.
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•The impacts of moisture and freeze-thaw damages on fracture properties were evaluated.•The semi-circular bending tests were conducted at intermediate and low temperatures.•Various levels of moisture and freeze-thaw damages were imposed on asphalt mixes.•The mode I critical stress intensity factor, fracture energy, and J-integral were calculated.•An approach was proposed to rank the long-term fracture resistance of asphalt mixes.
This study aims to quantify the fracture properties of asphalt mixes varying degrees of moisture and freeze-thaw damages. The frequent occurrence of moisture and freeze-thaw cycles are predominant environmental damages in asphalt pavement. These factors not only can cause distresses in asphalt mixes but also can accelerate damages caused by traffic loading and reduce the resistances of asphalt mixes against cracking. It is known that different asphalt mixtures can give different ranks of fracture properties under varying degrees of moisture and freeze-thaw damages. Thus, fracture characteristics at varying levels of environmental damage are needed to rank the fracture resistance. In this paper, to study the fracture properties of asphalt mixtures, the semi-circular bending (SCB) tests were conducted on neat and modified asphalt mixtures after experiencing varying cycles of moisture and freeze-thaw. Then, the load and displacement at failure, the mode I critical stress intensity factor (KIC), strain energy (U), critical strain energy release rate (Jc), and fracture energy (Gf) were calculated to identify the damage level at each cycle of moisture and freeze-thaw damages. To incorporate the impacts of moisture and freeze-thaw damages on the service life, we defined the area under the critical strain energy release rate (Jc) and fracture energy (Gf) versus the service time as an indication of the overall fracture resistance of asphalt mixtures. The results show that the area under the curve of the fracture property versus service time can offer a proper index to investigate the long-term fracture resistance of asphalt mixtures. The proposed approach can concurrently address the fracture resistances of the asphalt mixture to moisture and freeze-thaw damages at different environmental conditions and damage evolution rates over service time.