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In order to understand the energy consumption and environmental pollution level of Shanxi highway construction, the life cycle environmental and energy impact assessment of asphalt mixture and cement concrete were conducted. One representative cement concrete pavement and two asphalt mixtures highways were selected for quantitative evaluation and LCA analysis. The total energy consumption values of Taichang highway are 20 % higher than that of the Dayun highway. The global warming potential indicators of Taichang (asphalt mixture), Dayun (asphalt mixture), and Deda (cement concrete) are 181 kg eq.CO2, 285 kg eq.CO2, and 330 kg eq.CO2, respectively during the materials production stage. The results indicated that the environmental effects of global warming had the biggest impact on the life cycle of the asphalt mixtures and the respective highways. Based on the study results, environmental pollution was highest on the Taichang highway whilst the Deda highway had the highest values of freshwater toxicity. Furthermore, energy consumption during the construction stage and environmental impacts at the end-of-life stage were found to be alarmingly high. Thus, reducing the energy consumption during the material preparation and highway construction stages as well as controlling the environmental pollutants and emissions during service are key to conserving energy, preserving the surrounding environment, and optimizing the life cycle of Shanxi highways.

In recent years, lignin has been receiving more coverage as an asphalt modifier because of its wide variety of sources, low price, renewability, and potential to improve the performance of asphalt pavement. This research aims to develop lignin-modified asphalt by adding soda lignin powder in different proportions to overcome some drawbacks of traditional modified asphalt. A series of tests, including empirical, viscosity, rutting, fatigue, cracking, storage stability, and chemical tests, were performed to determine the influence of soda lignin on asphalt binder. Test results revealed that the addition of lignin helps to reduce the temperature sensitivity of the asphalt by increasing its hardness and decreasing its ductility. At the same time, the incorporation of soda lignin powder also increased the viscosity of base asphalt with the increase in lignin content. Furthermore, rheological performance test results revealed that the addition of soda lignin significantly enhanced the rutting resistance and fatigue performance for all the dosages incorporated. And also, a slight reduction in low-temperature cracking performance was observed. In addition, the storage stability test result depicted that the dispersion of lignin powder in asphalt was comparatively uniform and stable, indicating excellent thermal storage stability for all the lignin amounts incorporated. Moreover, chemical test results suggest that the soda lignin and bitumen can be mixed physically without new chemicals.

Adoption of renewable energy sources such as biomass has been increasing worldwide. In this study, fast pyrolysis as an acceptable and viable method to get renewable bio-oil and biochar is used. Different temperatures and N2 flow velocities were used in the fast pyrolysis process to evaluate the pyrolysis yield of biochar and bio-oil. The waste wood and pig manure were utilized to prepare biochar and bio-oil. X-ray fluorescence, X-ray diffraction, high-pressure liquid chromatograph, Micro confocal laser Raman spectrometer, Fourier transform infrared spectrometer, and dynamic shear rheometer were used to measure the chemical compositions, structure, and pyrolysis yield of biochar and bio-oil. The obtained results indicate that pyrolysis temperature increases the purity of inorganic oxide in biochar and N2 flow velocity promotes the yield of carbon in biochar. The increase of N2 flow velocity would increase the acid property of bio-oil and damage the products yield of bio-oil. It was also observed that biochar could remarkably alter the fundamental performances of petroleum asphalt including penetration, softening point, ductility, viscosity, and complex modulus. The most important is that the upgraded bio-oil can be used to replace partly or fully the petroleum asphalt which is a promising biomass application.

Presence of moisture can weaken the asphalt-aggregate bond and result in aggregate stripping and moisture damage in asphalt mixture. This study investigates how the moisture affects the asphalt-aggregate bond and simulates moisture distribution of nano-scale in asphalt-aggregate interface. Effects of aggregate type (basalt, dolomite and limestone minerals), humidity and hydraulic pressure on moisture diffusion in asphalt-aggregate interface are studied. Diffusion coefficient (D), radial distribution function (RDF), contact angle (CA), free volume (FV) are calculated through molecular dynamic simulations. Polarizability of moisture in the asphalt-aggregate interface was measured using density function theory (DFT). Nano-scale moisture migration model in the asphalt-aggregate interface is built for the first time. The results show that D depends more on the hydraulic pressure than humidity and aggregate type which represents the significance of hydraulic pressure on the moisture diffusion. In addition, the aggregate type has significant effects on RDF, CA and FV. DFT results indicate that polarizability of moisture changes for different types of aggregate and hydraulic pressure values. In the asphalt-water-aggregate interface, the asphalt competitively interacts with moisture and ions from minerals through intermolecular forces.

Volatile organic compounds (VOCs) emission not only cause the environmental pollution, but also severely threaten human health as they are known to be toxic and carcinogenic. This study investigates the effects of biochar on removing the VOCs emission from asphalt. The biochar was obtained from the pyrolyzed productions of pig manure, waste wood and straw biomasses. Molecular model for the adsorption of the VOCs was developed and used to measure the adsorption energy and heat. The VOCs removal model was built and used to determine the VOCs removal mechanism in the asphalt. The results showed that biochar could remove alkanes, polycyclic aromatic hydrocarbons (PAHs) and sulphide compounds because of its intrinsic carbon negativity and porosity. Furthermore, source of the biochar was an influential factor on the adsorption of the VOCs compounds. Based on the results, waste wood-based biochar had the best adsorption performance which could be related to the amorphous carbon, graphite and its porous structure. Also, it shows that biochar has the great potential to be used as VOCs inhibitors.

To understand the prospects of rubber-modified and polymer-modified asphaltic materials, pavement engineers must have a proper knowledge of the physical mechanisms of polymer materials in asphalt binder so that asphalt materials reflect the various rheological properties and pavement distresses along the wide range of testing conditions. Accordingly, the study reported here is aimed to present a mechanistic investigation on characteristics of rubber-modified and polymer-modified asphalt binders based on the evaluation of various rheological properties and primary modes of failure (i.e. low-temperature cracking, rutting and fatigue cracking in this study). In this experimental work, crumb rubber (hereinafter referred to as rubber), styrene–butadiene styrene (SBS), and ethylene–vinyl acetate (EVA), were introduced individually to the asphalt binder at different rates to prepare the blends. The physical and mechanical characteristics of the modified asphalt binders were discussed in the light of rotational viscosity (before and after aging), linear and nonlinear rheological measurements, rutting susceptibility, fatigue cracking, and relaxation modulus. Susceptibility to low-temperature cracking also was analyzed for all possible aging states. The results revealed that the viscosity of modified asphalt binders (using rubber, SBS, and EVA) is highly dependent on the aging state and the additive type and the content. The modified binders are able to allow good stress relaxation and better resistance to low-temperature cracking (even after short- and long-term aging), rutting, and fatigue cracking. Interestingly, the low-temperature cracking performance of the SBS-modified asphalt binder had improved much more after long-term aging compared to the unmodified binder and rubber/EVA modified binders. EVA-modified binder can sustain higher strains than rubber-modified binder (RMB), while comparing both small and large shear strain measurements. Storage and viscous moduli were determined to identify the rheological properties along the range of linear and nonlinear domains, and polymer-modified binders (PMBs) showed higher moduli in linear and nonlinear rheological conditions compared to the unmodified binder. Likely, higher cross-linking generated by polymer is the main contributory cause of such result. EVA polymer is a good choice to mitigate rutting, whereas SBS is more helpful to control fatigue cracking of the binders.

Bio-asphalt replaced petroleum-asphalt for paving asphalt pavements, which is a technology with a wide range of application prospect. This work is aimed at improving the performance of aged bio-oil modified asphalt (bio-asphalt) for use in road pavement construction. Biochar and bio-oil are renewable resources and use in this research that are pyrolyzed from waste wood. The effects of different aging conditions on biochar-modified bio-asphalt and ordinary bio-asphalt were investigated in terms of their chemical functional groups, molecular formulas, radius distribution functions, rheological parameters, and phase separation. The aging conditions considered in this research are short-term aging, ultraviolet (UV) aging, pressure aging vessel (PAV), and low-temperature hardening. Biochar plays a significant role in the UV aging process. This study found that, with an increase in biochar modification, the alkyl group numbers increased and the sulfoxide and carbonyl numbers decreased during the aging process of bio-asphalt. It also shows that the inclusion of biochar improved the aging resistance of the bio-asphalt, but that biochar modification did not affect the bio-asphalt’s low-temperature hardening performance. Four asphalt components were studied: saturates, asphaltenes, resins, and aromatics (SARA). The effects of biochar on saturates and aromatics were significant, and the biochar was able to adsorb these components. This study also found that, with an increase in UV aging and PAV, the phase separation grows.

The paper at hand focuses on modeling the stress response of different mastics and asphalt binders exposed to small and large shear strains using Bergstrom-Boyce (BB) constitutive model as well as Finite Element (FE) approach. In this paper, a set of experiments based on Large Amplitude Oscillatory Shear (LAOS) test were designed and conducted to capture the state of strain dependence of bituminous mastics and binders over a broad spectrum of strain domain (0.5%, 10%, 20%, 30%, and 40%) pertaining linear and nonlinear regimes of such materials. Using the experimental data, the BB constitutive model was utilized to describe the attained behavior at two temperatures (30 °C and 40 °C) and varied strain amplitudes. The material properties derived from the BB model were further implemented into a Finite Element Model (FEM) using the ABAQUS platform to simulate the stress response of bituminous materials for a wide range of strain amplitudes. It has been shown that the bituminous mastics and binders have strong nonlinearity at high strain amplitudes, depicted graphically based on the progressive distortion from the elliptical form of Lissajous-Bowditch (LB) plot. Based on the observed goodness of fitting, the BB model well-described the experimental results for linear and nonlinear behaviors. Using the optimized parameters, it was confirmed that the BB model is well suited to build a numerical model that could reproduce stress responses derived from the LAOS results for a wide range of strain levels. The advantage of the methodology presented herein allows adaptable model constants of the BB model depending on the imposed level of strain and temperature and hence, the FEM can describe both linear and nonlinear behaviors of bituminous mastics and binders. From this paper, researchers can take advantage of capturing the stress response of binders and mastics under small and large strain amplitudes to stimulate the research on better representation of the complex behavior of asphalt mixes based on the role of mastic and asphalt binder.

Quantitative analysis was conducted in this study using a three-dimensional field microscope, scanning electron microscope, energy dispersive spectroscopy, and molecular simulation to investigate the surface and interface adhesive properties of three fine aggregate asphalt mixtures (FAM): basalt, steel slag, and andesite. The roughness of the aggregate and the contact angle of the asphalt on the aggregate surfaces also were analyzed quantitatively. Molecular dynamics simulations were carried out to evaluate the adhesive properties, molecular diffusion, and interfacial failure mechanisms of the basalt-, steel slag-, and andesite-based FAM. The average roughness values of the basalt, steel slag, and andesite were found to be 138.2 µm, 244.0 µm, and 185.2 µm, respectively. The stripping percentages of the basalt, steel slag, and andesite were 11.3%, 3.3%, and 10.8%, respectively. The diffusion coefficients of the resins (3.32 × 10−9 m2/s) and asphaltenes (3.05 × 10−9 m2/s) were higher than the diffusion coefficient of the oils (2.98 × 10−9 m2/s). The results indicate that the surface roughness and adhesive capacity of the aggregate used in this study can be ranked in decreasing order as steel slag, andesite, and basalt. The asphaltenes and resins contributed to the asphalt’s increased adhesion to the aggregate particles. Both adhesive and cohesive failure were found for the basalt-, steel slag-, and andesite-based FAM, but the steel slag FAM exhibited more cohesive failure, whereas the basalt and andesite FAM exhibited more adhesive failure.

Flow-induced crystallization (FIC) in polymers is an important problem that occurs on a very rapid time scale. This study aims to evaluate the flow-induced crystallization of bio-asphalt modified with different contents of biochar under various aging conditions. Small angle X-ray scattering and molecular dynamic simulations were performed to impose extensional deformation and the nucleation process. The rheological properties were measured using the dynamic shear rheometer (DSR) and the morphology of biochar modified bio-asphalt (BMBA) was measured using an optical microscope. The relative scattering intensity during crystallization appeared to peak at four strain rates: 13.2 s−1, 19.6 s−1, 25.4 s−1, and 27.3 s−1. The results showed that the addition of biochar could improve the flow-induced crystallization and enhance the high-temperature properties of bio-asphalt. Moreover, crystallization status of BMBA is lamellar crystals. Ultraviolet and pressure aging vessel aging could remarkably affect the crystallization status of BMBA and promote the formation of crystals.

Warm mix asphalt (WMA) is good technique to reduce temperature of 20–30 °C. It has developed for more than a decade, but it is still challenging to determine the mixing and compaction temperatures of asphalt mixture. The objective of this study is to use a “equi-torque temperature” method that determin the mixing and compaction temperatures conveniently and accurately. The workability of WMA was measured by a prototype workability device. A criterion torque range was proposed by measuring the workability of mixtures with virgin bitumen. Three different warm-mix additives (including Aspha-Min®, Sasobit®, and Evotherm DAT®) were studied by identical SBS modified asphalt mixture to assess the reasonableness of the mixing and compaction temperatures determined according to the torque range. The results indicated that the criterion torque range was reasonable and the production temperatures of WMA mixtures determined in this study were approximately consistent with other references. The final performance tests also indicated that the “equi-torque temperature” methodology was feasible and effective.

A phase change material (PCM) has a significant capacity to store thermal energy. Because of the complex and tough environment of a highway such as traffic load, drainage, and ultraviolet light, the recent studies on PCM cannot be directly applied to highway construction. The composite shape-stabilized phase change material (CPCM) was prepared by using a membrane layer to encapsulate the PCM to ensure stability. Preparation of the CPCM in highway construction discussed in this research includes: (a) CPCM material properties, (b) proper proportioning for preparing the CPCM by Scanning Electronic Microscope (SEM), Differential Scanning Calorimetric (DSC) and the orthogonal test. CPCM was developed using Teradecane, silica, Ethyl Cellulose (EC) and a dispersant. Performance of the CPCM due to the influence of EC and a dispersant also studied to determine exact proportions used in the CPCM. The optimized ratio of Teradecane, silica, EC and dispersant is 1:1:0.1:0.1. Phase change enthalpy of the PCM was calculated to be 178 J/g and the phase change temperature was determined to be 5.8 °C.