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Waterborne polyurethane asphalt emulsion (WPUA) is an environmentally friendly bituminous material, whose performance is highly dependent on the phase structure of the continuous phase. In this paper, WPUAs in the vicinity of phase inversion were prepared using waterborne polyurethane (WPU) and asphalt emulsion. The chemical structures, thermal stability, dynamic mechanical properties, phase-separated morphology and mechanical performance of WPUAs were studied. Fourier-transform infrared (FTIR) spectra revealed that there are no –NCO bonds in either the pure WPU or WPUAs. Moreover, the preparation of WPUA is a physical process. The addition of WPU weakens the thermal stability of asphalt emulsion. WPU improves the storage modulus of asphalt emulsion at lower and higher temperatures. The glass transition temperatures of the WPUA films are higher than that of the pure WPU film. When the WPU concentration increases from 30 wt% to 40 wt%, phase inversion occurs; that is, the continuous phase shifts from asphalt to WPU. The WPUA films have lower tensile strength and toughness than the pure WPU film. However, the elongations at break of the WPUA films are higher than that of the pure WPU film. Both the tensile strength and toughness of the WPUA films increase with the WPU concentration. Due to the occurrence of phase inversion, the elongation at break, tensile strength and toughness of the WPUA film containing 30 wt% WPU are increased by 29%, 250% and 369%, respectively, compared to the film with 40 wt% WPU. [ABSTRACT FROM AUTHOR]

This paper deals with the impact of polymer loading on the microstructure, viscosity, thermal properties and mechanical performance of recycled polyethylene (rPE) modified epoxy asphalt binder. With this aim, rPE was used as a modifier to improve the toughness of a hot-mix epoxy asphalt binder. rPE particles were found to be highly swollen by the asphalt. Double phase separation was observed in rPE modified epoxy asphalt binders: asphalts dispersed in the continuous epoxy phase and rPE particles distributed in the discontinuous asphalt phase. The viscosity of epoxy asphalt binders increased with more rPE contents but the allowable construction time for pavement remained long. Results revealed that the thermal stability of epoxy asphalt binders was slightly improved with the addition of rPE. Furthermore, rPE lowered the glass transition temperature and increased the storage modulus at the rubbery state. All rPE modified epoxy asphalt binders performed better damping behaviours. In addition, at low rPE concentrations, the mechanical properties of epoxy asphalt binders were improved while at rPE loading higher than 2%, the results were opposite. [ABSTRACT FROM AUTHOR]

Sasobit has been widely applied as warm-mix asphalt (WMA) additive in an environment friendly and energy saving pavement construction. Epoxy asphalt (EA) has been extensively used on the pavement of steel bridge decks. In the present paper, Sasobit was introduced into warm-mix epoxy asphalt binder (WEAB) to prepare Sasobit modified WEAB. The effect of Sasobit on the viscosity, thermal, damping and mechanical properties and morphology of the neat WEAB were investigated using various characterisation techniques. Sasobit significantly lowered the viscosity of the neat WEAB and prolonged the operational lifetime for mixture pavement. Sasobit lowered the glass transition temperature of the neat WEAB. Sasobit slightly decreases the damping properties and thermal stability of the neat WEAB. However, Sasobit increased the tensile strength of the neat WEAB. The crystalline network structures of Sasobit formed in asphalts were clearly observed. The lamellar crystalline structure of Sasobit turned to gel-like structure in curly ribbon shape with an increase of the WMA additive contents. Reaction-induced phase separation occurred in the neat WEAB and Sasobit modified WEABs. No crystalline network structures of Sasobit were observed in the dispersed asphalt phase of the modified WEABs. Sasobit decreased the size of asphalt particles in the continuous epoxy phase. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) with 0.2, 0.5, and 1.0 wt% loading was used to modify warm‐mix epoxy asphalt binders (WEABs). The thermal stability, structure of GO, rotational viscosity‐curing time performance, dynamic moduli, glass transitions, damping ability, mechanical performance, and phase‐separated morphology of GO/epoxy asphalt composites were investigated in the laboratory. GO significantly enhanced the thermal stability of the pure WEAB. X‐ray scattering analysis revealed that GO layers were delaminated in the epoxy asphalt binder. GO accelerated the cure reaction of the pure WEAB and thus resulted in higher rotational viscosity of GO/epoxy asphalt composites. Furthermore, the viscosity of the modified WEABs slightly increased in the GO content. GO increased the dynamic moduli and Tgs of both epoxy and asphalt for the pure WEAB. However, the damping ability of GO/epoxy asphalt composites was similar to that of the pure WEAB. Confocal microscopy observations revealed that GO was dispersed in both asphalt and epoxy phases of the phase‐separated WEAB. The asphalt domains in the continuous epoxy phase became more spherical and uniform with the existence of GO. Moreover, the dispersion of epoxy in the discontinuous asphalt phase became more evident. The mechanical properties of the pure WEAB were greatly improved with the addition of GO. The tensile toughness and strength of the pure WEAB increased by 31% and 33%, respectively, with the addition of 0.2 wt% GO. [ABSTRACT FROM AUTHOR]

Highlights • Sasobit modified epoxy asphalt rubber (EAR) has been developed. • The addition of Sasobit lowers the viscosity and glass transition temperature of the neat EAR. • The inclusion of Sasobit increases the number of spherical AR particles in the continuous epoxy phase. • The mechanical properties of the neat EAR are enhanced with the addition 1 wt% Sasobit. Abstract The utilization of crumb rubber to produce asphalt rubber (AR) for asphalt mixture pavement has been proven to be an economical and environmental way for the disposal of waste tires. As one of the most significant thermosetting polymer modified asphalt with prominent performances, epoxy asphalt (EA) has been widely used on the pavement of steel bridge decks. In present study, the mixture of epoxy oligomer and curing agent was incorporated into AR to prepare epoxy asphalt rubber (EAR). To lower the viscosity of AR, a WMA additive, Sasobit was introduced into AR to prepare Sasobit modified EARs. The effects of Sasobit on the rotational viscosity, glass transition temperature (T g), damping performance, mechanical properties and phase-separated morphology of the neat EAR were investigated. The inclusion of Sasobit significantly decreased the viscosity of the neat EAR during the whole curing process and prolonged the operational lifetime for asphalt mixture pavement. The addition of Sasobit slightly decreased the T g of the neat EAR. The T g of Sasobit modified EARs decreased with WMA additive content increasing. Meanwhile, the presence of Sasobit improved the damping properties of the neat EAR. The existence of Sasobit enhanced the mechanical properties of the neat EAR at lower WMA additive concentration. The mechanical properties of Sasobit modified EARs decreased with increasing WMA additive content. Morphological observations revealed that the phase-separated microstructures of the neat EAR consisted of the dispersed spherical and co-continuous AR particles and the continuous epoxy phase. The existence of Sasobit decreased the number of co-continuous AR particles in the epoxy matrix. In addition, the number of co-continuous AR particles decreased with increasing WMA additive content. The presence of Sasobit decreased the average diameter of the dispersed AR particles and area fraction of AR domains in the neat EAR. [ABSTRACT FROM AUTHOR]

Styrene-butadiene-styrene triblock copolymer (SBS) and epoxy resin have been widely applied in asphalt modification. In the present work, industrial SBS-modified asphalt (SBA) was used to prepare epoxy SBS-modified asphalt (ESBA). The morphology, rheological, thermal and mechanical properties of ESBAs were characterized. LSCM observations revealed that the formation of phase-separated microstructures between epoxy and SBA in ESBAs. Secondary phase separation occurred in epoxy asphalts (EAs) with 50 and 60 wt% asphalts. The phase inversion occurred in epoxy asphalt with 60 wt% asphalt. In addition, the morphology of ESBAs also exhibited secondary phase separation. Two interlocked continuous phases appeared in SBA domains of ESBA with 40 wt% SBA. No phase inversion was observed in ESBA with 60 wt% SBA. The presence of SBS decreased the average size of dispersed domains in EA. The existence of SBS increased the initial viscosity of the epoxy asphalt during cure reaction. The viscosity of ESBA was low enough to satisfy the requirement for the pavement of steel bridge decks. The thermal stability of EA was enhanced with the existence of SBS. Furthermore, the presence of SBS significantly improved mechanical properties of the epoxy asphalt. Especially, the tensile strength, elongation at break and toughness of ESBA containing 60 wt% SBA were 125%, 55% and 113% higher than those of the epoxy asphalt with the same content of asphalt. [ABSTRACT FROM AUTHOR]

[Display omitted] • Core-shell rubbers (CSRs) with two core polymers have been used to toughen epoxy asphalt (EA). • 2 wt% CSR with polybutadiene (PB) core alters the phase separation mechanism of EA. • Both swollen polymer and asphalt particles form in the continuous epoxy phase of EA. • The area fraction of swollen PB particles is higher that of swollen SB particles. • EA modified by CSR with PB core exhibits higher damping and mechanical properties. Core-shell rubber (CSR) is a good candidate for toughening epoxy asphalt binders. However, the knowledge of the effect of the core polymer on the performance of CSR modified hot-mix epoxy asphalt binder (HEAB) is not completed and systematic yet. In this paper, CSR modified HEABs were prepared by the incorporation of 2 wt% CSR particles with different core polymers, which were in turn subjected to viscous measurements, confocal microscopy, thermogravimetric analysis, dynamic mechanical analysis and tensile tests. The results revealed that the viscosity of CSR with styrene-butadiene copolymer (SB) core (CSR SB) modified HEAB is higher than that of CSR with polybutadiene (PB) core (CSR PB) modified HEAB during curing. The shell destruction of CSR particles resulted in the swelling of the core polymers and dispersion of swollen core polymer particles in the epoxy phase in the micron scale along with asphalt particles. The phase separation of CSR PB modified HEAB occurred in the spinodal decomposition mode, which was different from the nucleation and growth mechanism of the neat and CSR SB modified HEABs. The area fraction of swollen PB particles in the CSR modified HEAB was greater than that of swollen SB particles. The core polymer had a negligible effect on the thermal stability of CSR modified HEABs. The glass transition temperatures of epoxy and asphalt, damping ability and mechanical properties of the neat HEAB were increased with the addition of CSR particles. Especially, CSR PB modified HEAB had higher tensile strength and toughness than CSR SB modified HEAB. With 2 wt% CSR PB particles being adding, the tensile strength, elongation at break and toughness of the neat HEAB were increased by 53%, 42% and 110%, respectively. [ABSTRACT FROM AUTHOR]

[Display omitted] • Eco-friendly fire-retarded warm-mix epoxy asphalt binders (WEABs) have been developed. • RPFR of significantly improved the fire retardancy of the pure WEAB. • RPFR hinders WEAB's cure reaction and extends the allowable construction time of WEAB mixtures. • RPFR improves the glass transition temperature and thermal stability of the pure WEAB. • Double phase separation forms in RPFR modified WEABs. Epoxy asphalt binder is flammable and plenty of fumes are produced during its high-temperature pavements in tunnels. To improve fire retardancy and reduce asphalt fumes, eco-friendly flame-retarded warm-mix epoxy asphalt binders (WEABs) for road tunnel pavements were developed by incorporation of reactive polymeric flame retardant (RPFR), which was composed of a reactive polymeric brominated epoxy oligomer (BEO) and antimony oxide. The influence of RPRF on flame retardancy, rotational viscosity, microstructures, thermal properties and mechanical performance of the pure WEAB was investigated using various techniques: oxygen index instrument, Brookfield viscometer, confocal microscope, differential scanning calorimeter, thermogravimetric analyzer and universal testing machine. The presence of RPFR significantly improved the limited oxygen index (LOI) of the pure WEAB. The LOI of RPFR modified WEABs increased in the flame retardant loading. The reaction of epoxide groups of RPFR with the curing agents of epoxy asphalt reduced the viscosity of the pure WEAB and extended the allowable construction time of the WEAB mixture. The inclusion of RPFR increased the glass transition temperature (T g) of the pure WEAB. For modified WEABs, the T g increased in the RPFR loading. RPFR reacted into the epoxy asphalt backbone through the reaction between epoxy groups and curing agents. The incorporation of RPFR improved the thermal stability of the pure WEAB. The addition of 8 wt% RPFR increased the tensile strength of the pure WEAB, while the inclusion of RPFR slightly decreased the break elongation of the pure WEAB. Double phase separation occurred in RPFR modified WEAB: the main phase separation included the continuous epoxy phase and the discontinuous asphalt domains, in which the secondary phase separation formed with asphalt as the continuous phase and spherical BEO domains as the discontinuous phase. The particle size of BEO domains decreased with the increase of the RPFR loading. [ABSTRACT FROM AUTHOR]

• Phase separation of ESBA disrupts the original dispersion of SBS in the asphalt. • The size of SBS domains in ESBAs increases in the SBS loading. • ESBA's viscosity increases in the SBS loading. • The thermal stability of ESBAs enhances with the increase of SBS loading. • The neat EA's elongation at break increases by 56% with the addition of 3 wt% SBS. Both styrene–butadiene-styrene copolymer (SBS) and epoxy resin have been widely applied in the asphalt modification. The influence of SBS concentration on the morphology, viscosity, thermal stability, glass transition temperature (T g), damping performance and mechanical behaviors of the neat EA binder was studied. Double phase separation occurred in the epoxy SBS modified asphalt (ESBA): main phase separation between epoxy and the SBS modified asphalt (SBA) and secondary phase separation between asphalt and SBS. The occurrence of phase separation in the ESBA disrupted the original dispersion of SBS particles in SBA and resulted in the redistribution of SBS in the form of smaller spherical particles. The inclusion of SBS increased the viscosity of the neat EA. Furthermore, the viscosity of ESBAs increased with the SBS content. ESBAs had as long as 150-min construction time for the mixture pavement. The presence of SBS improved the thermostability of the neat EA. In terms of ESBAs, the thermostability increased with the SBS content. The addition of SBS lowered the T g of the neat EA when the SBS content was lower than 4 wt%. The T g of ESBAs increased with the SBS content. The incorporation of SBS significantly enhanced the damping behaviors of the neat EA. The tensile strength of the neat EA was improved with the addition of 2 wt% SBS. The inclusion of SBS improved the elongation at break and the toughness of the neat EA when the SBS loading was greater than 1 wt%. [ABSTRACT FROM AUTHOR]

• Core-shell rubber (CSR) nanoparticle toughened epoxy asphalt (EA) has been developed. • The toughness of the pure EA increases by 2-fold with only addition of 1 wt% CSR. • The shell of CSR is broken and the core of CSR swells in the EA. • Newly micro-scale CSR phase uniformly disperses in the epoxy phase of the EA. • CSR nanoparticles alters the mechanism of phase separation of the pure EA. Core-shell rubber (CSR) has been widely applied in the improvement of the toughness for the brittle epoxy resin. In this study, an epoxy asphalt (EA) binder has been toughened by the inclusion of CSR nanoparticles with approximately 100–200 nm in diameter. The incorporation of CSR nanoparticles significantly increased the viscosity of the pure EA during curing. Even with 5 wt% CSR, the EA blend exhibited extremely long operational lifetime (more than 2.5 h) for mixture pavements. The glassy shell of CSR nanoparticles was broken and the rubbery core of CSR nanoparticles swelled in the EA. New micro-scale CSR domains formed and uniformly dispersed in the epoxy phase of the cured EA. The inclusion of CSR nanoparticles altered the phase separation mechanism of the pure EA. The sea-island morphology of the pure EA took place through the nucleation and growth (NG) mechanism, while co-continuous microstructures in the EA blends with 3 wt% and 5 wt% CSR formed through the spinodal decomposition (SD) mechanism. Both sea-island and co-continuous microstructures via combined the NG and SD mechanisms were observed in the EA blend containing 1 wt% CSR. The glass transition temperature and thermal stability of the pure EA was improved by the inclusion of higher CSR loadings. The incorporation of CSR greatly enhanced the mechanical properties of the pure EA. In the case of 1 wt% CSR inclusion, 29% increase in the tensile strength, 60% improvement in the elongation at break and 2-fold increment in the toughness were obtained. [ABSTRACT FROM AUTHOR]

• Waste cooking oil (WCO) modified epoxy asphalt binder (EAB) has been developed. • WCO lowers the viscosity and thus extends the construction time of the neat EAB. • Phase inversion in WEAB occurs when 6 wt% WCO is added. • WCO improves the low-temperature performance of the neat EAB. • WCO enhances the damping properties and thermal stability of the neat EAB. Waste cooking oil (WCO) was used as a warm mix asphalt (WMA) additive to modify warm-mix asphalt binder (WEAB) with the expectation of lowering the viscosity and prolonging the construction time of the binder. The viscosity, phase separation, viscoelasticity, thermostability and mechanical properties of WCO modified WEABs were studied and compared with the neat WEAB. WCO significantly reduced the WEAB's viscosity and extended the construction time of the neat WEAB. Moreover, the reducing and prolonging effects increased with the WCO content. Phase-inverted microstructure and secondary phase separation formed in the modified WEAB with 6 wt% WCO. The inclusion of WCO improved the low-temperature performance of the neat WEAB. The damping behavior and thermostability of the neat WEAB were improved with the inclusion of WCO. The presence of WCO increased the elongation at break of the neat WEAB when the waste oil content was lower than 4 wt%. [ABSTRACT FROM AUTHOR]

• Brominated SBS (BrSBS) modified epoxy asphalt (EBrSA) binder has been developed. • The nucleophilic substitution reaction occurs between BrSBS and amine curing agent. • Phase inversion takes place in the EBrSAs with higher BrSBS contents. • The flame retardancy of the neat HEAB is significantly improved by BrSBS. • BrSBS greatly increases the glass transition temperature of the neat HEAB. Brominated styrene–butadienestyrene triblock copolymer (BrSBS) is a novel polymeric flame retardant (PolyFR), which is eco-friendly due to its huge molecule weight. In this paper, BrSBS was added into an epoxy asphalt binder (EAB) to enhance the flame resistance of EAB. The microstructure, viscosity, fire resistance, thermal stability, dynamic mechanical behaviors and mechanical properties of BrSBS modified EABs (EBrSAs) were studied. Double phase separation occurred in EBrSAs. BrSBS modified asphalt (BrSA)-rich phase co-continuously dispersed in the continuous epoxy matrix when BrSBS content was lower. However, phase-inverted morphology appeared when the BrSBS content was higher. In other words, the epoxy-rich phase dispersed in the continuous BrSA-rich phase. The amine curing agent reacted with BrSBS through a bimolecular nucleophilic substitution (S N 2) mechanism, resulting in the formation of epoxy/BrSBS interpenetrating polymer networks (IPNs). The incorporation of BrSBS greatly increased the viscosity of the neat EAB due to the nucleophilic substitution reaction between BrSBS and amine curing agent. BrSBS with lower loading significantly improved the flame retardancy of the neat EAB. BrSBS lowered the thermal stability, mechanical and damping behaviors of the neat EAB. However, the glass transition temperature (T g) of the neat EAB was notably enhanced with the inclusion of BrSBS. [ABSTRACT FROM AUTHOR]