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SBS-modified bitumen (SMB) is susceptible to aging, which seriously influences its service performance and life. In order to strengthen the anti-aging ability of SMB, triethoxyvinylsilane was designed to organically modify layered double hydroxides (LDHs) and was applied to modify SMB. The dispersibility and storage stability of LDHs in SMB were markedly enhanced after triethoxyvinylsilane organic modification, and the compatibility and storage stability of SBS in bitumen were simultaneously enhanced. Compared with SMB, the introduction of LDHs and organic LDHs (OLDHs) could ameliorate the high-temperature properties of SMB, and the thermostability of SBS in bitumen at a high temperature was also distinctly improved, especially OLDHs. After aging, due to the oxidation of molecular bitumen and the degradation of molecular SBS, SMB became hardened and brittle, and the rheological properties were significantly deteriorated, which had serious impacts on the performance of SMB. LDHs can mitigate the detriment of aging to bitumen and SBS, and the deterioration of the rheological properties of SMB is obviously alleviated. As a result of the better dispersibility and storage stability, OLDHs exerted superior reinforcement of the anti-aging ability of SMB.
Canlin Zhang; Hongjun Dong; Zhengli Yan; Meng Yu; Ting Wang; Shi Xu; Zhenliang Jiang; Changbin Hu. SBS Modified Bitumen with Organic Layered Double Hydroxides: Compatibility and Aging Effects on Rheological Properties. Materials 2021, 14, 4201 .
AMA StyleCanlin Zhang, Hongjun Dong, Zhengli Yan, Meng Yu, Ting Wang, Shi Xu, Zhenliang Jiang, Changbin Hu. SBS Modified Bitumen with Organic Layered Double Hydroxides: Compatibility and Aging Effects on Rheological Properties. Materials. 2021; 14 (15):4201.
Chicago/Turabian StyleCanlin Zhang; Hongjun Dong; Zhengli Yan; Meng Yu; Ting Wang; Shi Xu; Zhenliang Jiang; Changbin Hu. 2021. "SBS Modified Bitumen with Organic Layered Double Hydroxides: Compatibility and Aging Effects on Rheological Properties." Materials 14, no. 15: 4201.
Self-healing asphalt, which is designed to achieve autonomic damage repair in asphalt pavement, offers a great life-extension prospect and therefore not only reduces pavement maintenance costs but also saves energy and reduces CO2 emissions. The combined asphalt self-healing system, incorporating both encapsulated rejuvenator and induction heating, can heal cracks with melted binder and aged binder rejuvenation, and the synergistic effect of the two technologies shows significant advantages in healing efficiency over the single self-healing method. This study explores the fatigue life extension prospect of the combined healing system in porous asphalt. To this aim, porous asphalt (PA) test specimens with various healing systems were prepared, including: (i) the capsule healing system, (ii) the induction healing system, (iii) the combined healing system and (iv) a reference system (without extrinsic healing). The fatigue properties of the PA samples were characterized by an indirect tensile fatigue test and a four-point bending fatigue test. Additionally, a 24-h rest period was designed to activate the built-in self-healing system(s) in the PA. Finally, a damaging and healing programme was employed to evaluate the fatigue damage healing efficiency of these systems. The results indicate that all these self-healing systems can extend the fatigue life of porous asphalt, while in the combined healing system, the gradual healing effect of the released rejuvenator from the capsules may contribute to a better induction healing effect in the damaging and healing cycles.
Shi Xu; Xueyan Liu; Amir Tabaković; Erik Schlangen. Experimental Investigation of the Performance of a Hybrid Self-Healing System in Porous Asphalt under Fatigue Loadings. Materials 2021, 14, 3415 .
AMA StyleShi Xu, Xueyan Liu, Amir Tabaković, Erik Schlangen. Experimental Investigation of the Performance of a Hybrid Self-Healing System in Porous Asphalt under Fatigue Loadings. Materials. 2021; 14 (12):3415.
Chicago/Turabian StyleShi Xu; Xueyan Liu; Amir Tabaković; Erik Schlangen. 2021. "Experimental Investigation of the Performance of a Hybrid Self-Healing System in Porous Asphalt under Fatigue Loadings." Materials 14, no. 12: 3415.
Aqueous solution is one of the main factors of asphalt pavement disease. However, the physicochemical changes of asphalt are ambiguous during immersion in different aqueous solutions. This study evaluated the physicochemical properties of asphalt under the action of different aqueous solutions to further understand the mechanism of moisture erosion. The morphology, chemical structure and four components of asphalt were observed after immersion, while the pH value, total organic carbon (TOC) and characteristic functional groups of residual solutions were monitored. The test results showed that aqueous solution could change the bee structure on the asphalt surface and increased the mean roughness. The carbonyl index (IC=O) and sulfoxide index (IS=O) of asphalt increased with immersion time. And the asphaltenes of asphalt fluctuated and eventually increased during immersion. Solute could accelerate the erosion on asphalt through interaction, the degree of which increased in the order, Na2SO4 saline < NaCl saline < pH 3 acid < pH 11 alkali.
Yingxue Zou; Serji Amirkhanian; Shi Xu; Yuanyuan Li; Yafei Wang; Jianwei Zhang. Effect of different aqueous solutions on physicochemical properties of asphalt binder. Construction and Building Materials 2021, 286, 122810 .
AMA StyleYingxue Zou, Serji Amirkhanian, Shi Xu, Yuanyuan Li, Yafei Wang, Jianwei Zhang. Effect of different aqueous solutions on physicochemical properties of asphalt binder. Construction and Building Materials. 2021; 286 ():122810.
Chicago/Turabian StyleYingxue Zou; Serji Amirkhanian; Shi Xu; Yuanyuan Li; Yafei Wang; Jianwei Zhang. 2021. "Effect of different aqueous solutions on physicochemical properties of asphalt binder." Construction and Building Materials 286, no. : 122810.
Microwave heating has been shown to be an effective method of heating asphalt concrete and in turn healing the damage. As such, microwave heating holds great potential in rapid (1–3 min) and effective damage healing, resulting in improvement in the service life, safety, and sustainability of asphalt pavement. This study focused on the microwave healing effect on porous asphalt concrete. Steel wool fibres were incorporated into porous asphalt to improve the microwave heating efficiency, and the optimum microwave heating time was determined. Afterwards, the microwave healing efficiency was evaluated using a semi–circular bending and healing programme. The results show that the microwave healing effect is largely determined by the steel fibre content and the mix design of the porous asphalt concrete.. Besides, the uneven heating effect of microwave contributes to an unstable damage recovery in the asphalt mixture, which makes it less efficient than induction heating. However, microwaves exhibited the ability to penetrate further into the depth of the test specimen and heat beneath the surface, indicating deeper damage recovery prospects.
Shi Xu; Xueyan Liu; Amir Tabaković; Erik Schlangen. The Prospect of Microwave Heating: Towards a Faster and Deeper Crack Healing in Asphalt Pavement. Processes 2021, 9, 507 .
AMA StyleShi Xu, Xueyan Liu, Amir Tabaković, Erik Schlangen. The Prospect of Microwave Heating: Towards a Faster and Deeper Crack Healing in Asphalt Pavement. Processes. 2021; 9 (3):507.
Chicago/Turabian StyleShi Xu; Xueyan Liu; Amir Tabaković; Erik Schlangen. 2021. "The Prospect of Microwave Heating: Towards a Faster and Deeper Crack Healing in Asphalt Pavement." Processes 9, no. 3: 507.
Rejuvenator encapsulation technique showed great potential for extrinsic asphalt pavement damage healing. Once the capsules are embedded within asphalt pavement, the healing is activated on-demand via progressing microcrack. When the microcrack encounters the capsule, the fracture energy at the tip opens the capsule and releases the rejuvenator. Then the released rejuvenator wets the crack surfaces, diffuses into and softens the aged bitumen, allowing two broken edges to come in the contact, preventing further asphalt pavement deterioration. The quality and speed of the damage repair process strongly depend on the quality of rejuvenator, thus it is important to choose a proper rejuvenator with good abilities to restore the lost properties of bitumen from ageing and show a sustainable performance after healing. To this aim, three different rejuvenators were studied and ranked based on the performance of their rejuvenated bitumen, including physical properties, rheological properties, chemical properties and the performance after re-ageing. Furthermore, these rejuvenators were encapsulated in calcium alginate capsules and the tests on these capsules indicate the diameter, mechanical resistance and thermal stability of the capsules are influenced by the encapsulated rejuvenator. The findings will benefit the development of rejuvenator encapsulation technique and the optimization of the capsule healing system towards a better healing effect in asphalt pavement.
S. Xu; X. Liu; A. Tabaković; P. Lin; Y. Zhang; S. Nahar; B.J. Lommerts; E. Schlangen. The role of rejuvenators in embedded damage healing for asphalt pavement. Materials & Design 2021, 202, 109564 .
AMA StyleS. Xu, X. Liu, A. Tabaković, P. Lin, Y. Zhang, S. Nahar, B.J. Lommerts, E. Schlangen. The role of rejuvenators in embedded damage healing for asphalt pavement. Materials & Design. 2021; 202 ():109564.
Chicago/Turabian StyleS. Xu; X. Liu; A. Tabaković; P. Lin; Y. Zhang; S. Nahar; B.J. Lommerts; E. Schlangen. 2021. "The role of rejuvenators in embedded damage healing for asphalt pavement." Materials & Design 202, no. : 109564.
The rejuvenator dosage in bituminous binders is critical, as it has to be balanced to ensure the restoration of rheological properties without over-softening the recycled binders. In this study, the impact of dosage of different rejuvenators on a polymer modified bitumen was evaluated by conducting rheological tests at low, medium and high temperatures using a dynamic shear rheometer. This paper also presents the results from a differential scanning calorimetry in an effort to assess the glass transition of new recycled binders. The results indicate that the complex modulus and phase angle, Glover-Rowe parameter and glass transition temperature can be successfully used to evaluate the effectiveness of rejuvenators. Moreover, the maximum and minimum rejuvenator dosage was selected by performing multiple stress creep recovery and frequency sweep tests, respectively, and particularly by balancing between creep compliance and complex modulus results. Compared with the commercial rejuvenators, the lab prepared rejuvenator can effectively recover the cracking and fatigue resistance, without dramatically scarifying the rutting resistance. Overall, a procedure was proposed to select the appropriate dosage and type of rejuvenator for polymer modified binders toward engineering durable and long-lasting recycled pavement materials.
Peng Lin; Xueyan Liu; Panos Apostolidis; Sandra Erkens; Shisong Ren; Shi Xu; Tom Scarpas; Weidong Huang. On the rejuvenator dosage optimization for aged SBS modified bitumen. Construction and Building Materials 2020, 271, 121913 .
AMA StylePeng Lin, Xueyan Liu, Panos Apostolidis, Sandra Erkens, Shisong Ren, Shi Xu, Tom Scarpas, Weidong Huang. On the rejuvenator dosage optimization for aged SBS modified bitumen. Construction and Building Materials. 2020; 271 ():121913.
Chicago/Turabian StylePeng Lin; Xueyan Liu; Panos Apostolidis; Sandra Erkens; Shisong Ren; Shi Xu; Tom Scarpas; Weidong Huang. 2020. "On the rejuvenator dosage optimization for aged SBS modified bitumen." Construction and Building Materials 271, no. : 121913.
Self-healing asphalt, aimed to produce a sustainable asphalt pavement using green technology, has been studied in the past two decades. Technologies including encapsulated rejuvenator and induction heating have been proposed, demonstrated in the laboratory, and gradually evaluated in field application. This paper looks into the synergy effect of the above two technologies, where induction heating serves as the asphalt damage repair mechanism, requiring just 2 min heating time and encapsulated rejuvenator will replenish (rejuvenate) aged asphalt binder and reinstate bitumen’s healing ability. Moreover, the increased temperature from induction heating could in turn accelerate the diffusion process of rejuvenator into aged bitumen. In this paper, the healing efficiency of the combined healing system was tested in comparison with autonomous asphalt healing system, induction healing system and capsule healing system. Porous asphalt concrete with various healing systems were prepared and a laboratory ageing procedure was followed to simulate the condition when healing was needed (after years of serving). X-ray computed tomography was employed to visualize the material composition and distribution inside of each healing systems. The properties of binder extracted from the porous asphalt samples were examined by dynamic shear rheometer. Indirect tensile strength and indirect tensile stiffness modulus tests were employed to characterize the mechanical properties of the porous asphalt samples with various healing systems. Finally, the cracking resistance of these healing systems was investigated by semi-circular bending test, and the healing efficiency was evaluated using a bending and healing programme. The results indicated that the combined healing system, with synergistic effects of aged binder rejuvenation and crack healing, shows a longer life extension prospect over the other healing systems.
S. Xu; X. Liu; A. Tabaković; Erik Schlangen. A novel self-healing system: Towards a sustainable porous asphalt. Journal of Cleaner Production 2020, 259, 120815 .
AMA StyleS. Xu, X. Liu, A. Tabaković, Erik Schlangen. A novel self-healing system: Towards a sustainable porous asphalt. Journal of Cleaner Production. 2020; 259 ():120815.
Chicago/Turabian StyleS. Xu; X. Liu; A. Tabaković; Erik Schlangen. 2020. "A novel self-healing system: Towards a sustainable porous asphalt." Journal of Cleaner Production 259, no. : 120815.
Induction healing is a proven technology which is able to improve the self-healing capacity of asphalt concrete. Healing is achieved via electromagnetic current produced by passing induction machine, where steel asphalt constituents heat up which in turn soften the bitumen in the asphalt layer, allowing it to flow and close cracks, repairing the damage. This paper reports on the study which investigated the influence of ageing on the healing capacity of Porous Asphalt (PA) concrete. Porous Asphalt concrete mix was prepared first, then subjected to an accelerated (laboratory) ageing process using a ventilated oven. In order to further evaluate the induction healing efficiency of asphalt concrete, Semi-circular bending (SCB) and healing cycles were performed on asphalt concrete specimens. The results show that with an increase of the ageing level of porous asphalt concrete, the induction healing efficiency decreases.
Shi Xu; Xueyan Liu; Amir Tabaković; Erik Schlangen. The influence of asphalt ageing on induction healing effect on porous asphalt concrete. RILEM Technical Letters 2019, 3, 98 -103.
AMA StyleShi Xu, Xueyan Liu, Amir Tabaković, Erik Schlangen. The influence of asphalt ageing on induction healing effect on porous asphalt concrete. RILEM Technical Letters. 2019; 3 ():98-103.
Chicago/Turabian StyleShi Xu; Xueyan Liu; Amir Tabaković; Erik Schlangen. 2019. "The influence of asphalt ageing on induction healing effect on porous asphalt concrete." RILEM Technical Letters 3, no. : 98-103.
It has been demonstrated that calcium alginate capsules can be used as an asphalt healing system by pre-placing rejuvenator (healing agent) into the asphalt mix and releasing the rejuvenator on demand (upon cracking). This healing mechanism relies on the properties of capsules which are determined by the capsule preparation process. In this study, to optimize the calcium alginate capsules, capsules are prepared using varying Alginate/Rejuvenator (A/R) ratios. Light microscope microscopy and Environmental Scanning Electron Microscope (ESEM) are employed to characterize the morphology and microstructure of these capsules. Thermal stability and mechanical property are investigated by thermogravimetric analysis (TGA) and compressive tests. The testing results indicate that higher alginate content results in smaller diameter and lower thermal resistance, but higher compressive strength. The optimum A/R ratio of calcium alginate capsules is found to be 30/70. To prove the effectiveness of the optimized capsules, the capsules are embedded in asphalt mortar beams and a bending and healing program is carried out. The effect of capsule shell material on the mechanical response of asphalt mixture is evaluated through three-point bending on the mortar beams embedded with blank capsules (without the healing agent). Aged mortar beams containing alginate capsules encapsulating rejuvenator demonstrate a higher strength recovery after bending tests, which indicates effective healing due to the release of the rejuvenators from the capsules.
Shi Xu; Amir Tabaković; Xueyan Liu; Damian Palin; Erik Schlangen. Optimization of the Calcium Alginate Capsules for Self-Healing Asphalt. Applied Sciences 2019, 9, 468 .
AMA StyleShi Xu, Amir Tabaković, Xueyan Liu, Damian Palin, Erik Schlangen. Optimization of the Calcium Alginate Capsules for Self-Healing Asphalt. Applied Sciences. 2019; 9 (3):468.
Chicago/Turabian StyleShi Xu; Amir Tabaković; Xueyan Liu; Damian Palin; Erik Schlangen. 2019. "Optimization of the Calcium Alginate Capsules for Self-Healing Asphalt." Applied Sciences 9, no. 3: 468.
Improving the healing capacity of asphalt is proving to be an effective method to prolong the service life of an asphalt pavement. The calcium alginate capsules encapsulating rejuvenator have been developed and proved to provide successful localized crack healing in asphalt mastic. However, it is not known whether this self-healing asphalt system will improve healing capacity of a full asphalt mix. To this aim, this paper reports on study which investigate effect of the calcium alginate capsules onto self-healing capacity of the porous asphalt mix. X-ray computed tomography (XCT) was used to visualize the distribution of the capsules in porous asphalt. The effect of the capsules on fracture resistance of porous asphalt concrete was studied by semi-circular bending (SCB) tests. A semi-circular bending and healing programme was carried out to evaluate the healing effect of these capsules in porous asphalt concrete. Indirect Tensile Stiffness Modulus (ITSM) tests were employed in order to investigate the influence of the capsules on the stiffness of the porous asphalt concrete. The results indicate that incorporating calcium alginate capsules significantly improve the healing capacity of porous asphalt concrete without compromising its performance.
Shi Xu; Xueyan Liu; Amir Tabaković; Erik Schlangen. Investigation of the Potential Use of Calcium Alginate Capsules for Self-Healing in Porous Asphalt Concrete. Materials 2019, 12, 168 .
AMA StyleShi Xu, Xueyan Liu, Amir Tabaković, Erik Schlangen. Investigation of the Potential Use of Calcium Alginate Capsules for Self-Healing in Porous Asphalt Concrete. Materials. 2019; 12 (1):168.
Chicago/Turabian StyleShi Xu; Xueyan Liu; Amir Tabaković; Erik Schlangen. 2019. "Investigation of the Potential Use of Calcium Alginate Capsules for Self-Healing in Porous Asphalt Concrete." Materials 12, no. 1: 168.
In recent decades, researchers have revealed the great healing potential of asphalt and proposed various novel methods to inspire and improve the self‐healing capacity of asphalt aimed to prolong the service life of asphalt pavement. In this review, up to date research progresses in induction healing and embedded rejuvenator encapsulation are presented, respectively. Meanwhile, the trial section applications of induction healing and capsule healing are highlighted, which show promising results. Finally, some recommendations for the future development of self‐healing asphalt are proposed.
Shi Xu; Alvaro García; Junfeng Su; Quantao Liu; Amir Tabaković; Erik Schlangen. Self-Healing Asphalt Review: From Idea to Practice. Advanced Materials Interfaces 2018, 5, 1 .
AMA StyleShi Xu, Alvaro García, Junfeng Su, Quantao Liu, Amir Tabaković, Erik Schlangen. Self-Healing Asphalt Review: From Idea to Practice. Advanced Materials Interfaces. 2018; 5 (17):1.
Chicago/Turabian StyleShi Xu; Alvaro García; Junfeng Su; Quantao Liu; Amir Tabaković; Erik Schlangen. 2018. "Self-Healing Asphalt Review: From Idea to Practice." Advanced Materials Interfaces 5, no. 17: 1.
Shi Xu; A. Tabaković; X. Liu; Erik Schlangen. Calcium alginate capsules encapsulating rejuvenator as healing system for asphalt mastic. Construction and Building Materials 2018, 169, 379 -387.
AMA StyleShi Xu, A. Tabaković, X. Liu, Erik Schlangen. Calcium alginate capsules encapsulating rejuvenator as healing system for asphalt mastic. Construction and Building Materials. 2018; 169 ():379-387.
Chicago/Turabian StyleShi Xu; A. Tabaković; X. Liu; Erik Schlangen. 2018. "Calcium alginate capsules encapsulating rejuvenator as healing system for asphalt mastic." Construction and Building Materials 169, no. : 379-387.