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• Oxidative aging promoted and further stabilized asphaltene aggregation. • The driving force for aggregation was dispersion between the fused aromatic cores. • All additives reduced asphaltene aggregation and improved orientational randomness. • TBC exhibited the highest potential due to spatial distribution of four polar sites. Economic and environmental sustainability has been a significant stimulus to the use of recycled asphalt materials in the pavement industry. In this practice, rejuvenators are usually required to treat the oxidized asphalts with the aim to restore the physical properties and engineering performance. A critical function required for rejuvenators is that they can deagglomerate the asphaltene aggregates by effectively interacting with them. This study employed the techniques of molecular dynamics simulations and quantum chemical calculations, and investigated the impacts of oxidation on asphaltenes and the deagglomerating potential of three selected additives with different molecular structures and polarities, i.e., tributyl citrate (TBC), limonene, and myristamide. Analyses based on the aggregation number, orientational order parameter, and decomposition of the interaction energy indicated that oxidation strengthened the binding between the asphaltenes and thus promoted their aggregation behaviors. Among the three additives, TBC exhibited the highest rejuvenating effectiveness as it restrained the formation of large asphaltene aggregates and improved the orientational randomness of the aromatic cores. This capability was attributed to the highest number of polar sites in TBC and its three-dimensional spatial structure, which enhanced the compatibility and interactions with the aged asphaltenes. Based on the independent gradient model (IGM) method, the asphaltene aggregation is driven by the π-π interactions dominated by dispersion forces between the fused aromatic cores. The additives weakened the asphaltene interactions to different degrees, but the reversing effects were limited compared to the unaged state. [ABSTRACT FROM AUTHOR]

This study aims to explore the feasibility of using dry flue gas desulphurization ash (DFGDA) as a filler in asphalt pavements. Two DFGDA materials were added into the base asphalt with different mineral powder proportions to prepare asphalt mastic and mixture, and the pure mineral powder asphalt mastic and mixture were used as the blank control group to evaluate the properties of DFGDA-doped asphalt mastic and mixture. The results show that the addition of DFGDA can improve the high-temperature rheological property and reduce the low-temperature rheological property of asphalt mastic; similarly, the high-temperature stability of asphalt mixture can be greatly improved, while its low-temperature performance and water stability are reduced; despite these decreases, all outcomes still meet the requirements of relevant specifications. No chemical reactions are observed between DFGDA and asphalt, indicating that the physicochemical properties of fillers are responsible for the change in the properties of DFGDA-doped slurry and mixture. Notably, the DFGDA-added asphalt mixture does not bring additional negative effects to the environment. Based on cost analysis, the high-quality use of DFGDA in asphalt mixture can save direct material costs of about $920,000 per 100 kilometers of asphalt road construction. In summary, the application of DFGDA in the asphalt mixture can not only meet the basic performance requirements of asphalt pavements but also greatly save material costs and protect the environment. • The feasibility of using DFGDA as an alternative filler in asphalt was examined. • DFGDA decreased the asphalt mastic strain and enhanced rutting resistance. • DFGDA reduced the low temperature performance and water stability of mixture. • Asphalt mastic performance depends on the physicochemical properties of fillers. • The application of DFGDA can save material costs and protect the environment. [ABSTRACT FROM AUTHOR]

• Moisture damage was induced in the PAM via freeze–thaw (F-T) cycling. • The PAM strength decreased with F-T cycle following an exponential decay function. • At higher stresses the PAM exhibited higher fatigue dependence on moisture damage. • Predictive models were developed for the single- and two-stage IDT fatigue loading. • Miner's sum M < 1 for the H-L sequence and M > 1 for the L-H sequence. This study investigated the fatigue behavior of a porous asphalt mixture (PAM) considering the effect of moisture damage. The PAM was designed with a high-viscosity asphalt and target air void of 20%. Moisture damage was induced through freeze–thaw (F-T) conditioning with 1, 3, 5, 10, and 15 cycles, and was quantified in terms of loss in the indirect tensile (IDT) strength. The IDT fatigue test with the single- and two-stage loading patterns was employed. Results indicated that the strength decreased with the number of F-T cycles following an exponential decay function. Moisture damage rendered the PAM more susceptible to fatigue loading, and at higher stress levels the material exhibited higher fatigue dependence on moisture damage. In the S-N relationships established from the single-stage fatigue characterization, the role of moisture damage was incorporated into the intercept and slope as exponential functions. The two-stage characterization resulted in the Miner's sum M < 1 for the high-to-low loading sequence, and M > 1 for the low-to-high sequence. The power-law nonlinear damage rule was adopted, in which the dependence of the exponent on moisture damage was found to follow an exponential decay function. In the predictive models developed for both loading patterns, the effects of moisture damage and loading level were mathematically described in uncoupled forms, as a result of no moisture damage progression during fatigue loading. [ABSTRACT FROM AUTHOR]

Compaction is a critical assurance for the quality and performance of asphalt pavement in terms of durability and serviceability. At present, there is a knowledge gap in the roller-pavement interaction in terms of energy variation during the process of asphalt pavement compaction. This paper aims to reveal the interaction and energy variation between the vibrating drum and pavement surface course during compaction process. Based on field tests, vibration signals of both the vibrating drum and pavement (i.e., the top, middle and bottom surface layers) were captured by acceleration sensors, and then the Hilbert marginal spectrum of the signals was obtained by the Hilbert-Huang Transform (HHT) for interpreting the signal features. Based on the marginal spectrum, the energy variation of the vibrating system (drum and pavement) during compaction was obtained. A predictive model of pavement compactness was further established according to the observed linear relationships between the pavement compactness and the energies of the vibrating system, and was then validated in the field application. The findings show that the energy-based approach adopted herein is able to not only characterize the compactness of asphalt pavement, but also reflect the uniformity of compaction. The developed relationships have a good potential as a useful tool for quality control in the field compaction practice. ● Mutual feedback and energy variation of roller-pavement interaction is investigated. ● Hilbert-Huang Transform is adopted to interpret vibration signal to capture energy feature. ● Marginal spectrum of signal energy is applied to characterize pavement compactness. ● Strong linear relation is revealed between pavement compactness and vibrating energy. ● Energy-based approach is able to reflect compaction uniformity of asphalt pavement. [ABSTRACT FROM AUTHOR]

• Dynamic responses of asphalt pavement in compaction were monitored using SmartRock. • Interaction characteristics between the steel drums and pavement surface were investigated. • The acceleration attenuation is normally distributed with the distance from the SmartRock. • A relationship was developed between the maximum acceleration and compaction degree. Compaction is the final critical step in the construction of asphalt pavements, but the dynamic response of the mixtures at the particle scale and its correlation with the compaction degree have received limited in-depth investigations. Based on the SmartRock sensor technique, this study is aimed for this inadequacy and to further understand the interaction characteristics (e.g., rolling speed, vibration range and contact width) between the steel drums and pavement surface during compaction at the particle scale. Meanwhile, the dynamic responses (i.e., acceleration frequency and amplitude) of the aggregates in the asphalt mixture were comprehensively investigated to establish the correlation between the acceleration amplitude and compaction degree of pavement. According to the results, the vibrating drum shows a higher compaction effectiveness than the driving drum in the z -direction. The acceleration frequency reflects the energy attenuation of vibration waves during vibrational compaction, and the attenuation of vibration acceleration is normally distributed with the distance from the SmartRock. Lastly, an empirical relationship was developed between the maximum acceleration and pavement compaction degree and can be used to provide reasonable estimations for the in-situ density. The findings are expected to shed light on the compaction mechanism of asphalt pavement, and to provide a potential approach/basis for improving the on-site quality control and decision-making during compaction. [ABSTRACT FROM AUTHOR]

• Weatherability of soil can be effectively improved by CGN. • The strength of solidified samples slightly increased with the dosage and curing time. • Under the appropriate dosage, color difference of solidified samples can meet principle of "repairing the old as the old". • Carbonation is the dominant reaction of CGN during the curing stage. Earthen site is a kind of preciously historic building constructed with soil as the building material. In northwestern China, the earthen sites are threatened because of environmental hazards, such as wind erosion, water erosion, and so on. Rammed reinforcement of the erosion area can improve the overall stability of the site. In addition, region formed by ramming reinforcement can be defined as ramming area. The formation of the ramming area is a new surface, and new interface between the ramming area and the original site is formed. Therefore, ramming area must meet principle of "repairing the old as the old" and maintain compatibility with the original earthen sites in terms of soil strength, permeability. Calcined ginger nuts is an environment-friendly and inorganic material that is emerging curing agent to reinforce the erosion area of the earthen site, which may make the reinforcement area to meet the above requirements. A series of tests were performed to verify its feasibility and investigate its solidified effects and mechanism. The study demonstrated that, with dosage and curing time increasing, the shear strength and unconfined compressive strength of solidified samples slightly improved and the permeability coefficient decreased with a small extent, the disintegration and shrinkage rate significantly decreased, and the total color difference value of samples increased as the sample became brighter. Furthermore, the mechanism of solidified soil has been studied by performing mercury injection, X-ray diffraction, and scanning electron micrograph tests under 25% dosage, which is proposed as the optimum dosage. The pore size decreased with increase of curing time as calcium carbonate content increased. Crystal type of calcium carbonate is mainly calcite—a material with high strength and cohesiveness. Thus, carbonation is the dominant reaction during the curing stage. Moreover, the crystal morphology of calcite changes from needle-stick calcite to flake. In conclusion, calcined ginger nuts can be used as curing agent for reinforcing the erosion area of earthen sites. [ABSTRACT FROM AUTHOR]

• A comprehensive evaluation method was proposed for the interfacial characterization. • A clear boundary was noted between melamine formaldehyde (MF) and the asphalts. • MF achieved better blending with the neat asphalt than with the polymer modified. • Addition of MF enhanced the diffusion of all components in both asphalts. Various microencapsulation technologies involving different shell and core materials have been proposed in the literature for improving the asphalt mixture performance. The interfacial characteristics including adhesion between the microcapsule shell and asphalt largely determines the synergistic rheology of the blend. This study evaluated the impacts of melamine formaldehyde (MF) resin as the shell material on the interface and bulk properties of a neat and styrene–butadienestyrene (SBS) modified asphalt binders using the techniques of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and molecular dynamics (MD) simulation. The clear interface without voids or cracks revealed in the SEM images suggested good adhesion between MF and both asphalts. Satisfactory interfacial binding was also suggested in the FT-IT results. The absorption peak strength of the neat asphalt was higher than that of SBS modified asphalt, and the binding of MF with neat asphalt was stronger than with the modified. The modified asphalt exhibited a slightly lower compatibility due to the high difference in the solubility parameter between SBS and MF, 9.783(J/cm−3)0.5. Introduction of MF promoted self-association of the asphaltenes and enhanced the diffusion of all the four fractions in both asphalt systems. Diffusion of the asphaltenes in the neat and modified asphalts saw the highest enhancement, which was increased to 5.3915 and 3.7893 (10-10m2s−1), respectively. Increase in diffusion coefficient was attributed to the high polarity and mobility of the MF molecules. [ABSTRACT FROM AUTHOR]

• SENB test is simulated by DEM to assess fracture characteristics of asphalt mixture. • 16 different notch offset are simulated to study the influence by test and simulation. • 3D macroscopic crack morphology and the main crack deflection angle are visualized. • Crack propagation mechanism and contact fracture rule of SENB test is characterized. The single-edge notched bend (SENB) test has been widely employed to characterize the low-temperature fracture characteristics of asphalt mixtures. In this test, the pre-fabricated notch is typically fixed at the beam midline, but variation in its location has a significant impact on the resulted crack resistance. This study utilized the three-dimensional discrete element method (DEM) and evaluated the 16 SENB test configurations with different notch offset levels (i.e., the eccentric SENB test). The simulation results are interpreted using macroscopic parameters including crack morphology, main crack deflection angle, mixed-mode parameter and effective mixed-mode fracture toughness, and also from the mesoscopic perspective (crack propagation mechanism and contact fracture rule). The macroscopic analysis shows that the crack morphology can be categorized into three types: pre-notch bending crack, mixed-mode crack, and bottom bending crack, and that the main crack deflection angle is affected by the stress concentration at the crack tip caused by the top load and beam bending deformation. Moreover, the low-temperature crack resistance is affected by the degree of the beam bending deformation and microcrack damage evolution. The load mixing degree is mainly affected by shear stresses for the pre-notched bending crack and by tensile stresses for the mixed-mode crack. At the meso -level, the DEM model provides a realistic visualization of the crack propagation process and accurately captures the mesoscopic contact failure mechanism in the crack propagation process using crack fragments. This study provides a new approach to understand better various fracture mechanisms of asphalt pavement from both the macro- and meso -perspectives. [ABSTRACT FROM AUTHOR]

• The model of pavement texture is obtained by CCD camera and 3D reconstruction. • A calibration plate is developed as a portable tool to measure MTD. • The slope of 3D model of pavement texture is eliminated by ICP algorithm. • Create datum reference plane and texture reference plane to analyze the model. • Calculate the texture depth of asphalt pavement with volume algorithm. The depth of an asphalt pavement structure is an important index used to reflect the anti-skid performance of the pavement, which directly affects the driving safety of vehicles. In the current specifications (e.g., China, European and American standards), the mean texture depth (MTD) of an asphalt pavement is generally measured by the sand-patch method (SPM). However, SPM is easily affected by the operator's subjective experience and experimental environment, resulting in low accuracy and high scatter in the data. In view of such shortcomings, a fast and accurate method to obtain the texture depth of asphalt pavement was proposed by designing a new test tool and a computer-aided calculation method. The multiocular vision theory was adopted to reconstruct a three-dimensional (3D) point cloud model of pavement texture. To reflect the concavity and convexity of pavement texture and eliminate the influence of pavement slope, the iterative closest point (ICP) algorithm was employed to obtain the datum reference plane (DRP). On this basis, the pentahedral volume calculation method suitable for evaluating the texture depth of an asphalt pavement was proposed. Laboratory experiment results using SPM were inverted by equal volume calculation to obtain the texture reference plane (TRP) and MTD'. Meanwhile, a 3D average maximum elevation (Avg.EL) algorithm was obtained by the evolution of two-dimensional mean profile depth (MPD). Furthermore, three parameters, namely MTD, MTD', and Avg.EL, were used to measure the texture depth of two field pavement sections in service. The experimental results showed that the correlation between MTD' and MTD was better than that between Avg.EL and MTD, and the degree of scatter was smaller. MTD' could be used directly as a reference value for MTD. In the present work, the 3D volume calculation method of asphalt pavement texture depth was proposed, which integrates the technical flow of image acquisition, model reconstruction, and algorithm analysis. The developed method provides a technical reference for the application of computer vision technology in the analysis of pavement texture depth. [ABSTRACT FROM AUTHOR]