@article{xue_gulzar_castorena_2024, title={Linear viscoelastic, viscoplastic, and damage characterization of recycled asphalt binders and mixtures containing recycling agents with long-term aging}, url={https://doi.org/10.1007/s11043-024-09721-4}, DOI={10.1007/s11043-024-09721-4}, journal={Mechanics of Time-Dependent Materials}, author={Xue, Lei Gabriel and Gulzar, Saqib and Castorena, Cassie}, year={2024}, month={Jun} }
 @article{gulzar_xue_preciado_fried_castorena_underwood_habbouche_boz_2024, title={Phenomenological modeling of aging and rejuvenation on asphalt binder fatigue characteristics}, volume={425}, ISSN={["1879-0526"]}, DOI={10.1016/j.conbuildmat.2024.135929}, abstractNote={Recycling agents (RAs) have been explored as additives to enhance the properties of recycled asphalt binders. Despite extensive research on RAs, a critical knowledge gap exists regarding their impact on fatigue cracking of asphalt binders, especially considering the aging processes. This study aims to comprehensively investigate the effects of recycling agents on the fatigue properties of asphalt binders, with a specific focus on the influence of aging and rejuvenation. The current Linear Amplitude Sweep (LAS) test analysis procedure is utilized to assess the fatigue properties, and the efficacy of existing LAS test-based indices is evaluated. Furthermore, a novel index based on the simplified viscoelastic continuum damage (S-VECD) theory framework is proposed to monitor changes in fatigue properties with aging and rejuvenation. A total of 26 recycled binder blends are studied and the results demonstrate that the proposed index consistently tracks the effects of aging and rejuvenation in recycled binder blends containing recycling agents. Additionally, cross-scale assessments are conducted by correlating the proposed index with mixture performance, specifically the Indirect Tensile-Cracking Test parameter (CTindex). The findings indicate that the proposed index exhibits a correlation with the CTindex after 1-day Long Term Aging testing and effectively captures the aging sensitivity across different scales.}, journal={CONSTRUCTION AND BUILDING MATERIALS}, author={Gulzar, Saqib and Xue, Lei and Preciado, Jaime and Fried, Andrew and Castorena, Cassie and Underwood, Benjamin Shane and Habbouche, Jhony and Boz, Ilker}, year={2024}, month={Apr} }
 @article{alvis_pape_xue_castorena_2023, title={Effects of Asphalt Mixture Constituents on the Recycled Binder Contribution}, volume={4}, ISSN={0361-1981 2169-4052}, url={http://dx.doi.org/10.1177/03611981231165021}, DOI={10.1177/03611981231165021}, abstractNote={ Reclaimed asphalt pavement (RAP) and recycled asphalt shingles (RAS) are incorporated into some asphalt mixtures produced today. The use of recycled asphalt materials (RAM) in asphalt mixtures encompasses engineering challenges pertaining to uncertainty in the proportion of the recycled binder that is in contact with and blends with the virgin binder in the asphalt mixture, termed recycled binder contribution (RBC) here. Recent research shows that agglomerations of RAM particles are the main cause of partial RBC. These agglomerations prevent recycled binder from interacting with the virgin binder. However, current practices generally assume complete RBC and a detailed understanding of the role of asphalt mixture constituents on RBC does not at present exist. The use of softer binders, extenders, and recycling agents has been proposed in high-RAM-content mixtures to restore recycled binder stiffness and embrittlement. However, the effects of asphalt binder variables as well as RAM type, source, and content on RBC is at present poorly understood. This paper aims to investigate the effects of asphalt mixture constituents on the RBC in asphalt mixtures using energy-dispersive x-ray spectroscopy (EDS) tracer-based microscopy analysis. It is found that the virgin binder, RAM type, and source significantly influence RBC in asphalt mixtures. However, RAP age level and content as well as additives are found to have only marginal impacts on RBC. }, journal={Transportation Research Record: Journal of the Transportation Research Board}, publisher={SAGE Publications}, author={Alvis, Maria Aparicio and Pape, Sonja and Xue, Lei Gabriel and Castorena, Cassie}, year={2023}, month={Apr}, pages={036119812311650} }
 @article{fried_xue_gulzar_preciado_underwood_castorena_2022, title={Evaluation of Recycling Agent and Extender Dosage Selection Procedures to Restore the High-Temperature Climatic Performance Grade}, volume={2676}, ISSN={0361-1981 2169-4052}, url={http://dx.doi.org/10.1177/03611981221074361}, DOI={10.1177/03611981221074361}, abstractNote={ Dosage selection is important for effective use of recycling agents and extenders in asphalt pavements. A standardized protocol for extender and recycling agent dosage selection does not presently exist. NCHRP Project 09-58 established a recycling agent dosage selection procedure that aims to restore the desired high-temperature grade of a blend of recycled binder, virgin binder, and additive. Their simplified procedure relies on the existence of class-specific relationships between the blended system high-temperature grade and additive content. Further, the dosage selection procedure assumes complete recycled binder availability. There is general consensus that complete recycled binder availability is not achieved in practice, which may yield asphalt mixtures with poor rutting performance. This study seeks to evaluate the universality of the slopes proposed in NCHRP Project 09-58 to both extenders and recycling agents and evaluate the rutting resistance of asphalt mixtures prepared using additive dosages selected to restore the high-temperature grade of the blended binder system. This study encompasses one reclaimed asphalt pavement (RAP) and one recycled asphalt shingles (RAS) mixture. Two extender and two recycling agent products were evaluated. The results indicate that different additive types yield different slopes of the blended system high-temperature grade versus additive content. The results also show that uncertainty should be accounted for when establishing a dosage selection procedure to ensure that the blended binder grade does not fall below the desired value. The rutting resistance of mixtures prepared using additive dosages intended to restore the high-temperature grade all passed recommended Hamburg wheel-track criteria. }, number={6}, journal={Transportation Research Record: Journal of the Transportation Research Board}, publisher={SAGE Publications}, author={Fried, Andrew and Xue, Lei Gabriel and Gulzar, Saqib and Preciado, Jaime and Underwood, B. Shane and Castorena, Cassie}, year={2022}, month={Feb}, pages={302–314} }
 @article{wang_xue_xie_cao_2020, title={Investigation on self-healing of neat and polymer modified asphalt binders}, volume={20}, ISSN={1644-9665}, url={http://dx.doi.org/10.1007/s43452-019-0006-8}, DOI={10.1007/s43452-019-0006-8}, number={2}, journal={Archives of Civil and Mechanical Engineering}, publisher={Springer Science and Business Media LLC}, author={Wang, C. and Xue, L. and Xie, W. and Cao, W.}, year={2020}, month={Mar} }
 @article{wang_xue_xie_you_yang_2018, title={Laboratory investigation on chemical and rheological properties of bio-asphalt binders incorporating waste cooking oil}, volume={167}, ISSN={0950-0618}, url={http://dx.doi.org/10.1016/j.conbuildmat.2018.02.038}, DOI={10.1016/j.conbuildmat.2018.02.038}, abstractNote={Recent efforts are being conducted to develop alternative asphalt binders from various bio-mass resources for future flexible pavements construction due to their renewability and the increasing costs of conventional petroleum-based asphalt. The objective of this paper is to investigate the potential of using the waste cooking oil (WCO) based bio-oil as a modifier for petroleum based neat asphalt binder and Styrene-Butadiene-Styrene (SBS) modified binder by means of chemical and rheological approaches. A series of tests were conducted for such purpose, including the infrared spectroscopy test, frequency sweep rheological test, multiple stress creep recovery test, and linear amplitude sweep test. The infrared spectroscopy results indicate identical chemical functional groups between the bio-oil and the petroleum asphalt binder though acid, ether, ester and alcohol compounds were also observed within the bio-oil. The bio-oil modified binders display increased carbonyl index with increasing the bio-oil percent weight whereas the sulfoxide index almost exhibits the same level as that of the control asphalt. Frequency sweep tests show that the bio-oil addition obviously decreased the binder stiffness according to the dynamic shear modulus master curve. Due to this softening effect from the bio-oil modifier, the weakened rutting resistance of bio-binders are demonstrated for both neat and SBS binders at the high temperature range. The fatigue life of bio-binders at intermediate temperature under cyclic fatigue loading are found to be significantly improved by increasing bio-oil content but the binder yield energy simultaneously decreased. It can be preliminarily concluded that the WCO based bio-oil tested in this study could be used as a potential bio-modifier to produce a sustainable asphalt binder.}, journal={Construction and Building Materials}, publisher={Elsevier BV}, author={Wang, Chao and Xue, Lei and Xie, Wei and You, Zhanping and Yang, Xu}, year={2018}, month={Apr}, pages={348–358} }
 @article{xue_xie_wang_wang_2017, title={Characterizing Fatigue Failure Behavior of Modified Asphalt Binders from Linear Amplitude Sweep Test}, volume={5}, ISSN={2572-889X}, url={http://dx.doi.org/10.12783/dtmse/ictim2017/9900}, DOI={10.12783/dtmse/ictim2017/9900}, abstractNote={The fatigue characteristics of asphalt binder contributes to the fatigue resistance of asphalt concrete and pavements. The linear amplitude sweep (LAS) test (AASHTO TP 101) has been developed as the accelerated testing procedure for fatigue specification of asphalt binders in the United States. Recently a newly energy-based fatigue failure definition and unified failure criterion have been proposed for improving the LAS procedure and data interpreting. However, these new improvements need more verification and calibration on more materials with different modifiers for distinguishing the fatigue performance. In this paper, the improved LAS testing procedure was applied on totally two neat asphalt binders and six modified asphalt binders, which covered the high modulus asphalt binders (HMABs), SBS modified binder, high viscosity (HV) binder and crumb rubber (CR) modified binder. Based on the simplified-viscoelastic continuum damage (S-VECD) modeling approach, three material properties of linear viscoelastic property, damage characteristic curve and failure criterion were characterized for fatigue life prediction of all tested binders. Test results indicates that the CR binder demonstrated the highest failure strain followed by the SBS and compound SBS+HV binders, HMABs and neat binders. Further results of predictive fatigue life also verified the best fatigue life of CR binder followed by SBS+HV binders, SBS binder and HMABs. The HV additives to SBS binder was found to linearly increase the binder fatigue lives and the HMAB-RA showed better fatigue performance than HMAB-PR. Generally, the fatigue life ranking determined from the multiple-loading rates of LAS tests is consistent to the failure strain results and thus, the failure strain identified from the standard LAS-5 test could be used as a fatigue performance parameter.}, number={ictim}, journal={DEStech Transactions on Materials Science and Engineering}, publisher={DEStech Publications}, author={Xue, Lei and Xie, Wei and Wang, Yang and Wang, Chao}, year={2017}, month={May} }