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Epoxy asphalt has been extensively utilized in the construction of long-span steel deck bridges. Due to its thermosetting nature, however, the end-of-life epoxy asphalt cannot be reclaimed as thermoplastic polymer modified asphalts. In this paper, recyclable epoxy asphalt vitrimers (EAVs) were developed by introducing bond-exchange reactions into epoxy resin with fatty acids as curing agents. The existence of asphalt accelerated the bond-exchange reaction of the epoxy vitrimer (EV). Furthermore, the relaxation time of EAVs decreased with the asphalt concentration. The recycling enhanced the storage modulus of EAVs at the glassy stage. However, the glass transition temperature remained after recycling. The recycling lowered the mechanical properties of EAVs. However, both tensile strength and elongation at break of EAVs increased with the recycling time. For EAV containing 45% asphalt binder, the tensile strength and elongation at break after three-time recycling were onefold and twofold higher than those after only one-time recycling. The use of renewable epoxy resin in the development of epoxy asphalt not only reduces the dependence on petroleum resources but also makes the recycling of epoxy asphalt feasible. [ABSTRACT FROM AUTHOR]

Epoxy asphalt mixtures have been extensively used in the construction of steel deck bridges. The fatigue cracking formed during long-term service has become the main failure of epoxy asphalt mixtures due to the inherent brittleness of epoxy resin. To improve the toughness of the mixture to resist fatigue cracking, graphene nanoplatelets (GNPs) were used to modify the warm-mix epoxy asphalt binder (WEAB). The thermal stability, viscosity-curing time behavior, phase separation, dynamic mechanical properties and mechanical performance of GNP modified WEABs were investigated by various techniques. The presence of GNPs enhanced the thermal stability of the neat WEAB. The addition of GNPs increased the viscosity of the neat WEAB at the later stage of cure reaction and thus shortened the allowable construction time of epoxy asphalt mixtures. However, the viscosities of all modified WEABs containing less than 1.0 wt% GNPs meet the general specifications of epoxy asphalt materials for paving roads and bridges. Confocal microscopy observation revealed that GNPs dispersed in the discontinuous asphalt phase of epoxy asphalt binder. Meanwhile, the existence of GNPs altered the phase-separated morphology of the neat WEAB. GNPs slightly lowered the glass transition temperatures of both epoxy and asphalt and the damping ability of the neat WEAB. GNPs significantly improved the mechanical properties of the neat WEAB, especially for their tensile strength and toughness, increased by 46% and 41%, respectively, with the addition of 0.2 wt% GNPs. [ABSTRACT FROM AUTHOR]

Asphaltenes tend to aggregate to nanoparticles or clusters in crude oil and solvents over a wide concentration and temperature range. In the present paper, asphaltenes extracted from the base asphalt was used as a filler to introduce into epoxy resin. The microstructure and evolution of asphaltenes aggregation in the epoxy resin were observed using laser scanning confocal microscopy. Furthermore, the effect of asphaltenes on the viscosity, dynamic mechanical behavior, thermostability, mechanical properties of epoxy resin was evaluated by Brookfield rotational viscometer, dynamic mechanical analysis, thermogravimetric analysis and universal testing machine. The presence of asphaltenes increased the viscosity of the neat epoxy during all stages of cure reaction. The viscosity of epoxy/asphaltenes composites increased with the filler concentration. Fractal asphaltenes aggregation formed in the composites with 1 mass% asphaltenes. Network microstructures of asphaltenes aggregation appeared in the epoxy phase with a further increase of asphaltenes content. Moreover, the increase of asphaltenes loading resulted in denser network microstructures in the epoxy matrix. Aggregation evolution revealed that asphaltenes particles redispersed evenly in the epoxy resin in the form of some aggregates at the beginning of curing. During the cure reaction of epoxy, asphaltenes aggregates started to agglomerate and grow to network microstructures. The presence of asphaltenes led to the enhancement of the storage modulus of the neat epoxy at the rubbery stage. The glass transition temperature (Tg) of the epoxy composites slightly increased with the increase of asphaltenes loading. The epoxy composite with 5 mass% asphaltenes had higher Tg than the neat epoxy. The inclusion of asphaltenes had a negligible effect on the damping properties and thermal stability of the neat epoxy. The aggregation and heterogeneous dispersion of asphaltenes resulted in the decrease of the tensile strength and elongation at break of the neat epoxy. However, the inclusion of asphaltenes significantly enhanced Young's modulus of the neat epoxy. Young's modulus of the neat epoxy was increased by more than fourfold with the addition of 5 mass% asphaltenes. [ABSTRACT FROM AUTHOR]

Epoxy asphalt bond coat (EABC) is one of the thermosetting polymer-modified asphalts, which has been widely employed as a strong waterproof bonding layer between the asphalt concrete and the orthotropic steel bridge deck. In the present work, the influences of asphalt content on the phase separation, viscosity, thermal stability, viscoelastic behavior, mechanical performance, pull-off strength, and adhesive performance of EABCs were characterized by various instruments. Laser scanning confocal microscopy observations showed that phase separation occurring in EABCs depended on the curing time. The asphalt merged to form large spherical particles in the continuous epoxy phase during the cure reaction. The size of asphalt particles increased in the asphalt content. Viscosities of EABCs were higher than that of the pure epoxy and increased with the asphalt content in the initial curing stage. However, the opposite trend was observed in the latter curing stage. The presence of asphalt slightly improved the glass transition temperature and the damping properties of the pristine epoxy. For EABCs, the damping behaviors slightly increased with the asphalt content. The thermal stability of the pristine epoxy was enhanced by the incorporation of asphalt. The addition of asphalt decreased the mechanical, adhesive properties, and pull-off strength of the pristine epoxy. What's more, these properties of EABCs decreased in the asphalt content. [ABSTRACT FROM AUTHOR]

Brittleness is an inherent shortcoming of epoxy resin which results in the longitudinal fatigue cracking of mixtures during the long service time of orthotropic steel deck bridges. In this paper, this problem was addressed by introducing a reactive thermoplastic elastomer, epoxidized styrene–butadiene–styrene copolymer (ESBS) into epoxy asphalt binder (EAB). Epoxy ESBS modified asphalts (EESBAs) with various epoxidation degrees were prepared. Double phase separation occurred in the EESBAs. In the EESBAs with 18% and 31% epoxidation degrees, most of ESBS domains dispersed on the edge of the secondary asphalt phase and in the epoxy phase. Furthermore, the size and number of ESBS domains decreased in the epoxidation degree. However, un-epoxidized SBS domains completely dispersed the asphalt phase and all ESBS domains moved to the epoxy phase when the epoxidation degree increased to 39%. In EESBAs, the average diameters of asphalt domains increased in the epoxidation degree. The inclusion of ESBS increased the viscosity of the pure EAB and the viscosity of EESBAs increased in the epoxidation degree. Nevertheless, all EESBAs had at least a 150-min allowable construction time. By adding 2 wt% ESBS with 39% epoxidation degree, the glass transition temperature (Tg) decreased. The Tg of EESBAs decreased in the epoxidation degree. The inclusion of ESBS greatly enhanced the damping properties of the pure EAB. The elongation at break and toughness of the pure EAB were remarkably increased by 263% and 93%, respectively, with the incorporation of 2 wt% ESBS with 39% epoxidation degree. Furthermore, the toughness of EESBAs increased in the epoxidation degree. [ABSTRACT FROM AUTHOR]

As the most important thermoplastic and thermosetting modifiers, styrene-butadiene-styrene triblock copolymer (SBS) and epoxy resin have been widely applied in asphalt modifications. In this paper, epoxy SBS-modified asphalts (ESBAs) were prepared with epoxy monomer, curing agent and SBS-modified asphalts (SBAs) with various styrene-butadiene structures, which in turn were subjected to laser scanning confocal microscopy (LSCM), viscous measurements, thermal analysis and tensile tests. The LSCM results revealed that both polymer-rich phase and fluorescent particle-rich phase were observed in the asphalt matrix. Moreover, the number of SBS particles in SBAs increased with the increase of styrene contents. The presence of SBS decreased the size of dispersed domains in the continuous epoxy phase of the neat epoxy asphalt binder (EAB). For ESBAs, a double phase separation occurred between SBA and epoxy in the continuous epoxy phase and between asphalt and SBS in the dispersed SBA phase. Both number and size of SBS domains in the dispersed SBA phase of ESBAs increased with the increase of styrene contents. The inclusion of styrenic polymers increased the viscosity of the neat EAB. The viscosity of ESBAs increased with the increase of average molecular weights of the styrenic polymers. The addition of styrenic polymers increased the glass transition temperature (Tg) and storage modulus (E′) of the neat EAB. Meanwhile, the inclusion of styrenic polymers weakened the damping properties of the neat EAB. The styrene-butadiene structures had little effect on the Tg and damping properties of ESBAs. The E′ of ESBAs decreased with the increase of styrene contents. The presence of SBS enhanced the thermal stability of the neat EAB. Tensile results showed that the addition of SBS increased the tensile strength of the neat EAB. [ABSTRACT FROM AUTHOR]