Performance Assessment of Self-Healing Polymer-Modified Bitumens by Evaluating the Suitability of Current Failure Definition, Failure Criterion, and Fatigue-Restoration Criteria

Abstract

Fatigue cracking is a common form of flexible pavement distress, which generally starts and spreads through bitumen. To address this issue, self-healing elastomer (SHE) modified bitumens were elaborated to assess whether these novel materials can overcome the neat asphalt (NA) fatigue performance and whether the current failure definition, failure criterion, and fatigue-restoration criteria can fit their performance. All bitumens were subjected to short-term and long-term aging. Linear amplitude sweep (LAS) test, LAS with rest period (LASH), and simplified viscoelastic-continuum-damage (S-VECD) model were utilized to appraise the behavior of the mentioned bitumens. The results showed that maximum stored pseudo-strain energy (PSE) and tau (τ) × N (number of loading cycles) failure definitions exhibited high efficiency to accommodate the fatigue life of NA and SHE-modified bitumens. Both failure criteria identified that SHE-modified bitumen (containing 1% of SHE) showed the highest increment of fatigue performance (67.1%) concerning NA. The failure criterion based on total released PSE, in terms of the area under the released PSE curve, was the only failure concept with high efficiency (R2 up to 0.999) to predict asphalt binder fatigue life. As well, the current framework to evaluate bitumen self-restoration failed to fully accommodate asphalt binder behavior, because bitumen with higher restoration could not exhibit greater fatigue performance. Consequently, a new procedure to assess this property including fatigue behavior was proposed, showing consistent results, and confirming that SHE-modified bitumen (containing 1% of SHE) exhibited the highest increment of fatigue performance (154.02%) after application of the rest period. Hence, the optimum SHE content in NA was 1%. Furthermore, it was found that a greater number of loading cycles to failure (Nf) did not ensure better fatigue performance and stored PSE influenced the bitumen fatigue behavior.

Development of a Framework for Assessing Bitumen Fatigue Cracking Performance under Different Temperatures and Aging Conditions

“…Table 1 shows the 70# NA physical properties used in this study, which is the continuation of the research work of ref. [23]. In summary, only the stored PSE peak as the failure definition and the G R based on TRPSE were effective in accommodating bitumen fatigue behavior.…”

“…Lv et al [23] confirmed that the stored PSE peak (failure definition) identifying the 𝑁 linked with long-term aged NA and self-healing poly bitumen (SPB). However, their study identified that bitumens with highe show greater fatigue behavior in terms of DCC analysis, demonstrating ranking inadequacies between the failure definition and DCC assessment.…”

“…Their study proposed a new parameter (but as it is based on τ, it is not convenient): the average reduction in C up to the failure point is used to determine N f . Lv et al [23] confirmed that the stored PSE peak (failure definition) is suitable for identifying the N f linked with long-term aged NA and self-healing polymer-modified bitumen (SPB). However, their study identified that bitumens with higher N f failed to show greater fatigue behavior in terms of DCC analysis, demonstrating performance ranking inadequacies between the failure definition and DCC assessment.…”

“…Lv et al [23] assessed the efficacy of the power law function between W R sum and SE [14] and G R in both terms of W R r,sum [8], with TRPSE [27] as the failure criteria. Their study concluded that only a G R based on TRPSE was able to properly accommodate the bitumen fatigue behavior, which confirms the superiority of this concept over the other two.…”

“…In summary, only the stored PSE peak as the failure definition and the G R based on TRPSE were effective in accommodating bitumen fatigue behavior. However, the current failure definition and DCC analysis fail in consistently ranking a group of bitumen fatigue performances [9,23]. This inadequacy could define a key point in selecting the most convenient asphalt binder for a specific project.…”