|Title:||Waterborne epoxy resin modified bitumen emulsion as a high-performance cold paving binder : working mechanism and engineering performance|
|Advisors:||Leng, Zhen (CEE)|
Asphalt emulsion mixtures
Hong Kong Polytechnic University -- Dissertations
|Department:||Department of Civil and Environmental Engineering|
|Pages:||xvii, 133 pages : color illustrations|
|Abstract:||Asphalt pavement is the major type of pavement worldwide for its various advantages, such as driving comfortability, low noise and ease of maintenance. However, the production and construction of conventional hot-mix asphalt (HMA) must be conducted at high temperature, leading to significant energy consumption and potential hazardous emissions. To address the environmental concerns of HMA, bitumen emulsion can be applied as a cold binder in place of asphalt cement, because its viscosity is low enough at ambient temperature to achieve good workability. Nevertheless, bitumen emulsion faces the major concern of poor mechanical performance especially at high service temperatures. Recently, waterborne epoxy resin has emerged as a promising high-performance modifier which can significantly improve the mechanical performance of bitumen emulsion, while maintaining its advantage of ambient temperature construction. However, the modification mechanism of waterborne epoxy resin and its effects on the microstructure, rheology, aging, and fatigue of bitumen emulsion have not been fully understood yet. To fill this gap, this study aims to investigate the modification mechanism of waterborne epoxy resin and comprehensively evaluate its effects on the performances of bitumen emulsion. To achieve the objectives of this study, a waterborne curing agent for epoxy resin was first synthesized in lab, which was then used to prepare the waterborne epoxy resin emulsion. The waterborne epoxy resin emulsion was subsequently mixed with bitumen emulsion in various percentages to produce the waterborne epoxy resin modified bitumen emulsions (WEMBEs), and the waterborne epoxy resin modified bitumen emulsion residues (WEBERs) were obtained after the drying process. Finally, comprehensive laboratory tests and constitutive modelling were conducted to characterize the properties of both WEMBEs and WEBERs, followed by a case study to demonstrate the performance of WEMBE as a tack coat material.|
The characterization tests conducted on the WEMBEs mainly include the confocal laser scanning microscopy (CLSM) test, zeta potential test, and viscosity test, which evaluates the morphology, stability, and viscosity properties of the WEMBEs, respectively. It was found that stability of bitumen emulsion was not affected by waterborne epoxy resin. All bitumen emulsions showed shear-thinning behavior within the low shear rate range (0-10 s-1). But within the high shear rate range (10-200 s-1), the pure bitumen emulsion behaved like a Newtonian fluid, while WEMBE showed shear-thickening behavior. To evaluate the performance of the WEBERs, the CLSM test, dynamic shear rheometer (DSR) test, pressure aging vessel (PAV) test, time-sweep and linear amplitude sweep (LAS) tests, boiling test, and bond strength test were conducted to characterize the distribution of waterborne epoxy resin in bitumen, the rheological properties, aging performance, fatigue performance and moisture susceptibility of the WEBERs, and the bonding between the WEMBEs and aggregate, respectively. The results indicated that the cured waterborne epoxy resin formed an inter-connected polymer-rich film when the waterborne epoxy resin content reached 3wt%. Such structure can dramatically improve the high temperature performance, fatigue resistance, aging resistance, adhesion with aggregate, and moisture damage resistance of the bitumen emulsion. Furthermore, it was found that the "2S2P1D" model can well describe the dynamic response of the WEBERs under loading in the frequency domain irrespective of the waterborne epoxy resin contents, and the Prony series can well fit the modulus data of the WEBERs in both the frequency and time domains. Overall, the outcome of this study suggested that waterborne epoxy resin can effectively improve the mechanical performance of bitumen emulsion. Apart from the tack coat application which has been explored in this study, WEMBE is also a very promising high-performance cold binder for various other paving applications, such as pavement surface treatment, cold recycling, and cold mixes.
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