مهدي ابراهيم زاده شيراز

Given the significant role of fatigue in reducing pavement durability, the necessity of understan‎ding long-term performance, an‎d the increasing use of polymers in pavement engineering, this study simultaneously eva‎luates the fatigue behavior of bitumen an‎d asphalt mixtures using the same analytical approach. Moreover, the LAS test results an‎d their associated failure criteria are validated, an‎d subsequently, a predictive model is developed to estimate the fatigue life of polymer-modified asphalt mixtures under different aging conditions. Initially, polymer-modified binders containing four different waxes, two domestically produced waxes (Slack wax an‎d recycled polyethylene wax) an‎d two imported waxes (Sasobit an‎d Deurex), as well as a wax-free polymer-modified binder were prepared. To investigate the differences among the selec‎ted waxes, a rotational viscosity test was conducted on the modified binders. The results showed that Deurex, Slack wax, recycled polyethylene wax, an‎d Sasobit reduced the viscosity of the polymer-modified binder by 46.5%, 29.9%, 26.5%, an‎d 23.2%, respectively. Subsequently, the modified binders were conditioned in the laboratory at four aging levels, an‎d their rheological properties were examined an‎d eva‎luated at each aging level. In addition, to assess the fatigue behavior an‎d resistance of the binders at intermediate temperatures an‎d their sensitivity to aging, the Linear Amplitude Sweep (LAS) test was employed, an‎d fatigue testing was conducted for all aging levels. The results indicated that the failure strain of all polymer-modified samples decreased by approximately 45% after 40 hours of aging in the PAV, with the greatest reduction observed for the recycled polyethylene wax. Slack wax was found to improve the fatigue life under both low-strain an‎d high-strain conditions, while Sasobit also enhanced the fatigue performance of the polymer-modified binder, ranking second after Slack wax. In contrast, Deurex an‎d recycled polyethylene wax exhibited adverse effects on the fatigue life of the polymer-modified binders. The results indicated that Slack wax can be considered an economical alternative; however, for regions where rutting is the dominant distress, combining this wax with Sasobit is recommended. Next, the results of the binder tests were eva‎luated using dynamic modulus an‎d fatigue tests conducted on asphalt mixture specimens. By comparing these findings with the fatigue-life analysis of the binders, it was observed that the influence of aging on the fatigue behavior of asphalt mixtures showed greater similarity to the effects of aging on binder fatigue life obtained through the pseudo-strain energy-based analytical method an‎d the maximum-stress failure criterion, with both exhibiting decreasing trends. Therefore, it is recommended that, for assessing the aging sensitivity of binders with similar base characteristics, the pseudo-strain energy-based method an‎d the maximum-stress criterion be employed. Finally, to predict the fatigue life of polymer-modified binders an‎d asphalt mixtures, two neural-network models with the same overall architecture but different numbers of hidden layers were developed an‎d their performance was eva‎luated. The results demonstrated that the proposed models were able to accurately capture the complex relationships among strain level, binder type, aging level, an‎d fatigue life at both scales. The binder model, with a simpler configuration, an‎d the asphalt-mixture model, with a more complex structure, were both capable of reliably predicting the fatigue behavior of the materials under various aging conditions.

،پيرشدگي، , ،ترك خوردگي خستگي، , ،مخلوط آسفالتي، , ،قير پليمري، , ،واكس، , ،شبكه عصبي مصنوعي،

،Aging، , ،Fatigue cracking، , ،Asphalt mixture، , ،Polymer-modified binder، , ،Wax، , ،Artificial Neural Network (ANN)،

Mehdi Ebrahimzadeh Shiraz

Mahmoud Ameri