Full metadata record
| DC Field | Value | Language |
|---|---|---|
| dc.contributor | Department of Civil and Environmental Engineering | en_US |
| dc.contributor.advisor | Leng, Zhen (CEE) | en_US |
| dc.creator | Yang, Bin | - |
| dc.identifier.uri | https://theses.lib.polyu.edu.hk/handle/200/13666 | - |
| dc.language | English | en_US |
| dc.publisher | Hong Kong Polytechnic University | en_US |
| dc.rights | All rights reserved | en_US |
| dc.title | Preventive maintenance of porous asphalt pavement through surface treatment asphalt emulsion : working mechanism and material optimization | en_US |
| dcterms.abstract | Porous asphalt (PA) pavement has been widely applied worldwide because of its numerous merits, such as improved drainage, reduced noise, and enhanced skid resistance. However, the open-graded structure of PA increases the susceptibility of bitumen to aging, which makes PA more vulnerable to the ravelling distress at the early stage compared to conventional dense-graded and gap-graded asphalt pavement. Several measures have been applied to alleviate ravelling, such as using polymer modified asphalt binders, adding fibers/anti-stripping additives, and substituting conventional asphalt binder with epoxy, but the ravelling destress is still of frequent occurrence after a few years of service. Therefore, an effective preventive maintenance technique is necessary to alleviate ravelling during the road service period. Recent field trials in Europe showed that spraying surface treatment (ST) asphalt emulsion to existing PA pavement could mitigate ravelling and extend its service life. However, despite limited field experience and lab results, the interaction mechanisms of ST emulsion in old PA mixture remains unclear. In addition, there is a lack of scientific effort on how to optimize the ST emulsion for this purpose. To fill these research gaps, this study aims to reveal the working mechanism of ST emulsion in PA and optimize the material design of ST emulsion for improving maintenance effectiveness through a multiscale investigation. | en_US |
| dcterms.abstract | At the macroscale, the key factors affecting the recovery efficiency of ST emulsion on the ravelling resistance of damaged PA were first investigated and the optimal application conditions of ST were determined. Subsequently, the effects of ST on the mechanical and functional properties of the damaged PA were systematically evaluated. The results showed that both application rate and solid content of ST emulsion have significant effects on the ravelling resistance recovery of the damaged PA mixtures. The optimum application rate of 0.6 kg/m2 and solid content of 60% were recommended. The negative effect of ST emulsion on the functional performance (e.g.: noise reduction, permeability, and skid resistance) of PA was found to be insignificant. Meanwhile, the ST treated PA mixtures achieved superior rutting, fatigue, and cracking resistances. | en_US |
| dcterms.abstract | At the mesoscale, the penetration behavior of ST emulsion in damaged PA was investigated by X-ray Computer Tomography (CT). A series of image-related MATLAB algorithms were developed to identify and quantify the penetration status of three selected ST scenarios. The spatial distribution of ST emulsion in the damaged PA presented a gradient characteristic along the depth direction. The ST application reshaped the interconnected pore microstructure, including the size, number, area, interconnectivity, and tortuosity of air voids. The PA specimen treated by the ST emulsion with an application rate of 0.6kg/m2 and a solid content of 60% showed the best coating efficiency and the best ravelling resistance among the three ST conditions. | en_US |
| dcterms.abstract | At the microscale, the diffusion phenomena between ST residues and aged asphalt mortars within PA mixtures were observed via the Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS). TiO2 nano powder was selected as a tracer to tag the ST emulsion. The PA specimen preparation and analysis method for SEM/EDS testing were developed. The results showed that the diffusion rate at 60 °C was approximately 5 times faster than that at 25 °C. Thus, it is recommended to spray ST emulsions on old PA pavements in hot weather to accelerate the diffusion efficiency. | en_US |
| dcterms.abstract | Due to the nonuniform distribution and slow diffusion efficiency of conventional asphalt emulsion in PA mixture, rejuvenator was added to optimize ST asphalt emulsion. It was suggested to be emulsified first before directly mixing with asphalt emulsion for better compatibility. The optimal dosage of rejuvenator emulsion was determined by balancing the apparent viscosity, wettability, and bonding strength of ST emulsion. The CT images revealed that the rejuvenator-optimized ST emulsion was uniformly distributed in the PA mixture with a higher coating efficiency, which improved the ravelling resistance of PA. The physicochemical analysis implied that the penetrated rejuvenator-optimized ST residues replenished new asphalt binders and softened aged asphalt binders, decreasing the molecular weight of aged asphalt binder. The rheological results showed the rejuvenator-optimized ST residues improved the stress relaxation property and cracking resistance of aged asphalt binders but might compromise rutting resistance. | en_US |
| dcterms.extent | xx, 170 pages : color illustrations | en_US |
| dcterms.isPartOf | PolyU Electronic Theses | en_US |
| dcterms.issued | 2025 | en_US |
| dcterms.educationalLevel | Ph.D. | en_US |
| dcterms.educationalLevel | All Doctorate | en_US |
| dcterms.LCSH | Pavements, Asphalt -- Maintenance and repair | en_US |
| dcterms.LCSH | Pavements -- Maintenance and repair | en_US |
| dcterms.LCSH | Asphalt emulsion mixtures | en_US |
| dcterms.LCSH | Hong Kong Polytechnic University -- Dissertations | en_US |
| dcterms.accessRights | open access | en_US |
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