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Improving bonding and mechanical strengths is important for the application of bond coats used in the construction of steel deck bridges. Graphene nanoplatelets (GNPs) are attractive nanofillers for polymer modification because of their low cost, ultra-high aspect ratio, and extraordinary thermal and mechanical performance. In this paper, GNPs were used to reinforce the epoxy asphalt bond coat (EABC). The morphology, viscosity–time behavior, contact angle, dynamic mechanical properties, and mechanical and bonding strengths of GNP-reinforced EABCs were investigated using laser confocal microscopy, a Brookfield rotational viscometer, a contact angle meter, dynamic mechanical analysis, a universal test machine, and single-lap shear and pull-off adhesion tests. GNP dispersed non-uniformly in the asphalt phase of EABC. The viscosity of the neat EABC was lowered with the inclusion of GNPs and thus the allowable construction time was extended. The existence of GNPs enhances the hydrophobicity of the neat EABC. When adding more than 0.2% GNP, the storage modulus, crosslinking density and glass transition temperatures of both asphalt and epoxy of the neat EABC increased. The mechanical and bonding properties of the neat EABC were greatly enhanced with the incorporation of GNPs. Furthermore, the mechanical and bonding strengths of the modified EABCs increased with the GNP content. GNP-reinforced EABCs can be utilized in the pavement of long-span steel bridges with long durability. [ABSTRACT FROM AUTHOR]

The application of crumb rubber from end-of-life tires and waste cooking oil (WCO) in road pavements is of significant importance from an economic and environmental viewpoint. However, the incorporation of crumb rubber greatly shortens the allowable construction time of epoxy asphalt binders due to the high viscosity of the epoxy asphalt rubber (EAR) binder and poor compatibility between crumb rubber and asphalt binder. To lower the viscosity of asphalt rubber, extend the allowable construction time and improve the compatibility of EAR binder, waste cooking oil (WCO) was introduced. The effect of WCO on the viscosity–time behavior, thermal stability, dynamic modulus, glass transitions, crosslink density, damping ability, compatibility, mechanical properties and phase separation of WCO-modified EAR binders was investigated by using the Brookfield viscometer, thermogravimetric analysis, dynamic mechanical analysis, universal testing machine and laser confocal microscopy. The test results demonstrated that the incorporation of WCO declined the viscosity and extended the allowable construction time of the unmodified EAR binder. The inclusion of WCO improved the compatibility between asphalt and crumb rubber and the damping ability and elongation at the break of the unmodified EAR binder. The presence of WCO had a marginal effect on the thermal stability of the unmodified EAR binder. Confocal microscopy observation revealed that asphalt rubber particles aggregated in the epoxy phase of the unmodified EAR binder. With the inclusion of WCO, co-continuous asphalt rubber particles became more spherical. [ABSTRACT FROM AUTHOR]

Bisphenol A epoxy resin cured with a mixture of dimerized and trimerized fatty acids is the first epoxy vitrimer and has been extensively studied. However, the cure behavior and thermal and mechanical properties of this epoxy vitrimer depend on the epoxy/acid stoichiometry. To address these issues, epoxy vitrimers with three epoxy/acid stoichiometries (9:11, 1:1 and 11:9) were prepared and recycled four times. Differential scanning calorimetry (DSC) was used to study the cure behavior of the original epoxy vitrimers. The dynamic mechanical properties and mechanical performance of the original and recycled epoxy vitrimers were investigated by using dynamic mechanical analysis (DMA) and a universal testing machine. Furthermore, the reaction mechanism of epoxy vitrimer with different epoxy/acid stoichiometry was interpreted. With an increase in the epoxy/acid ratio, the reaction rate, swelling ratio, glass transition temperature and mechanical properties of the original epoxy vitrimers decreased, whereas the gel content increased. The recycling decreased the swelling ratio and elongation at break of the original epoxy vitrimers. Moreover, the elongation at break of the recycled epoxy vitrimers decreased with the epoxy/acid ratio at the same recycling time. However, the gel content, tensile strength and toughness of the original epoxy vitrimers increased after the recycling. The mechanical properties of epoxy vitrimers can be tuned with the variation in the epoxy/acid stoichiometry. [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) has been widely used as a bonding layer in the construction of orthotropic steel deck bridges. To withstand the vibration of the steel deck, EABC needs to have strong bonding strength. In present article, sodium montmorillonite (Mt) was used to reinforce the neat EABC. The morphology and properties of EABC/Mt nanocomposites were characterized by scanning electron microscopy, X‐ray diffraction, Brookfield rotational viscometer, dynamic mechanical analysis, thermogravimetric analysis, automatic adhesion tester, and universal testing machine. No intercalation structure formed in the EABC/Mt nanocomposites. Mt dispersed uniformly in the EABC matrix. The inclusion of Mt increased the viscosity of the neat EABC in the initial stage of chemical reaction. Whereas, in the later curing stage, the viscosity of the neat EABC was higher than those of EABC/Mt nanocomposites. The presence of Mt slightly reduced the glass transition temperature of the neat EABC. The damping performance of the neat EABC was improved with the inclusion of 1 wt% Mt. Mt had a marginal effect on the thermal stability of the neat EABC. The incorporation of Mt significantly enhanced the mechanical properties of the neat EABC. The tensile strength and toughness of the neat EABC increased by 30% and 26%, respectively, with the inclusion of 3 wt% Mt. The existence of Mt greatly enhanced adhesion strength of the neat EABC. The lap‐shear adhesion strength and pull‐off adhesion strength of the EABC nanocomposite with 5 wt% Mt were 33% and 29% higher than those of the neat EABC. [ABSTRACT FROM AUTHOR]

• Performance of epoxy asphalt binders and bond coats during and after curing is reviewed. • Phase separation evolution and final phase-separated morphology of epoxy asphatls are discussed. • The effect of additives on the properties and phase separation of epoxy asphalts is addressed. • Difference between thermoplastic and thermosetting polymer modified asphalts is compared. • The future outlooks of epoxy asphalts is highlighted. Epoxy asphalt is a unique representative of thermosetting polymer modified asphalt, which has been widely used in the construction of orthotropic steel deck bridges. This paper reviewed the performance and phase separation of epoxy asphalt binders and bond coats. To well understand the characteristics of the main components of epoxy asphalts, epoxy resin and asphalt were introduced. The history and classification of epoxy asphalt were described. The importance of viscosity-curing time behavior for controlling the allowable construction time of epoxy asphalt mixtures was discussed due to the reactive nature of epoxy asphalt binders. The factors that affect the mechanical and bonding properties and thermal stability of epoxy asphalt were analyzed. Cure behaviors of epoxy asphalts characterized by different models of differential scanning calorimetry (DSC) were compared. The relationship between dynamic shear rheometry (DSR) and dynamic mechanical analysis (DMA) for studying the viscoelastic properties of epoxy asphalt was interpreted. The two glass transitions, damping properties and Cole-Cole plots of epoxy asphalt obtained by DMA were reviewed. Although scanning electron microscopy (SEM) and fluorescence microscopy (FM) can be used to observe the phase-separated microstructures of epoxy asphalts to some extent, there were still some disadvantages, such as the inability for observation of phase separation evolution, difficulty in sample preparation and low contrast and resolution. The principle of laser scanning confocal microscopy (LSCM) with high image resolution and contrast was introduced. The phase separation mechanism of epoxy asphalt and polymer modified epoxy asphalts was compared. Influence of phase-separated morphology on the mechanical properties of cured epoxy asphalts and polymer modified epoxy asphalts was analyzed. [ABSTRACT FROM AUTHOR]

• Epoxy asphalt binders with three different epoxy oligomer contents have been developed. • Viscosity of epoxy asphalt binders decreases in the oligomer content. • Allowable construction time of epoxy asphalt binders increased in the oligomer content. • Glass transition temperatures of both epoxy and asphalt increases in the oligomer content. • The damping ability and tensile strength of epoxy asphalt binders increase in the oligomer content. The impact of oligomer content on the viscosity, dynamic mechanical properties and mechanical behaviors of hot-mix epoxy asphalt binders was investigated by Brookfield viscometer, dynamic mechanical analysis and universal testing machine. The viscosity of epoxy asphalt binders during curing decreased in the oligomer content. However, the allowable construction time increased with the oligomer content. The storage modulus of epoxy asphalt binders at the glassy stage decreased in the oligomer content, whereas an opposite trend appeared at the rubbery stage. Epoxy asphalt binders exhibited two glass transition temperatures (T g s) for both epoxy resin and asphalt, and increased in the epoxy oligomer content. The T g of epoxy of epoxy asphalt binder increased from 30.9 to 42.4 °C when the mass fraction of oligomer increased from 23.5 % to 25.5 %. The damping properties and tensile strength of epoxy asphalt binders increased in the oligomer content, while the elongation at break and toughness showed a contrary trend. The tensile strength of epoxy asphalt binder with 23.5 % oligomer was only 0.89 MPa, which was much lower than the specification required. [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]