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Utilizing treated plant fibers in fiber-modified asphalt could reduce reliance on nonrenewable resources, contributing to environmental sustainability. To promote the utilization of plant fibers in asphalt mixtures, this review focuses on elucidating the reaction mechanism of surface-treated plant fibers and the resulting performance benefits in the composite. A comprehensive review of reinforcement mechanisms of fibers in composites, particularly asphalt mixtures, is provided to gain a mechanistic understanding of how fibers enhance performance. The review incorporates multiple perspectives to provide a thorough understanding of the performance-enhancing effects of fibers within asphalt. Plant fibers have significant potential to improve several aspects of asphalt mix performance, including high-temperature stability, low-temperature crack resistance, moisture stability, and fatigue durability. These properties also influence the optimal loading and fiber length for different fiber types, and this review provides a comprehensive overview along with recommended values. In addition, microscopic studies play a critical role in understanding the mechanism of plant fibers in asphalt mixes. The review discusses the microscopic changes induced by fiber surface treatment and sheds light on their effects at a fundamental level. The review provides a holistic reference for the application of plant fibers in asphalt mixtures for guiding asphalt pavement engineering applications, and prospect on the research direction of plant fibers in asphalt mixtures. [ABSTRACT FROM AUTHOR]

With the growth of service time, semirigid base asphalt pavements have gradually entered the maintenance and reconstruction period. Therefore, the treatment of waste semirigid bases has become an important issue. In this paper, based on the analysis of the properties of cement-stabilized gravel milling material, the waste semirigid base material is cold recycled using foam asphalt. The mechanical properties of the cold recycled mixture of foamed asphalt formed by 100% cement-stabilized gravel milling material (FACRM-CM) were evaluated by splitting strength test, compressive modulus of resilience test, and dynamic modulus test. The softening mechanism of the semirigid base milling material was investigated from a microscopic point of view with the aid of scanning electron microscopy (SEM). The results indicate that FACRM-CM exhibits adequate mechanical strength for use in road base layers. When semirigid base milling materials are cold recycled using foam asphalt, the stiffness of the resulting mixture decreases, whereas its flexibility increases. The results of this research can be applied to the regeneration of semirigid bases, realizing the transformation of the base from rigidity to flexibility and reducing pavement diseases. [ABSTRACT FROM AUTHOR]

The interface between asphalt and aggregate directly determines the performance of asphalt mixtures but unavoidable weaknesses can be easily found at the interfacial bonding region. In order to evaluate the interfacial adhesion behavior between asphalt and aggregate at the atomic scale, asphalt binders and two mineral aggregates (quartz and calcite) were selected to build molecular models and molecular dynamics (MD) simulations were conducted. The interfacial energy between asphalt and aggregate was calculated and the mineral aggregate has a more significant influence on the energy compared to the binder types. Also, the simulation result indicates that saturate, aromatic, resin, and asphaltene (SARA) components have different interfacial energies with respect to the aggregates. This result can also be derived from the relative concentration of SARA components on the aggregate surface. Additionally, oxidation of the asphalt binder results in increased interfacial energy due to the enhanced intermolecular bonding generated by oxidized functional groups. The intrusion of water greatly reduces the interfacial energy, but the energy increases under the coupling effect of oxidation and moisture, especially for calcite. The grey relational grade theory was conducted to evaluate the factors affecting the adhesive energy, and the results show that the energy of the asphalt-aggregate is more sensitive to the asphaltene index than other factors. [ABSTRACT FROM AUTHOR]

This article aims to propose an asphalt mixture with deicing and permeable functions to address the dilemma of excessive stormwater runoff during summer and ice accumulation in winter for pavement in southwest China. A peeling test and ice melting test were first conducted to select one powder and one granular anti-icing additive for better deicing performance. Then the effects of anti-icing additive contents on deicing and pavement performance of deicing permeable mixtures were investigated to select the best content. Additionally, the effect of immersion treatment on the pavement performance of deicing permeable mixture was analyzed. The results showed that the rise in additives content would help to improve deicing performance, as expected, regardless of additive type. The optimal content of the powder additive was reached by replacing 80% of the mineral powder, and the optimal mass ratio of granular type was 5% of the mixture. The addition of additives weakened the low-temperature performance and water-stability performance of the permeable mixture, whereas a high-temperature performance was observed when granular additive was adopted. The pavement performance of the mixture with granular additive was better than the mixture with powder additive under different immersion treatments. Overall, the granular anti-icing additive is recommended for use in a permeable mixture. This research is helpful and may provide guidance for the design of deicing permeable asphalt mixtures. [ABSTRACT FROM AUTHOR]

Because of the relatively low accuracy of the current asphalt pavement performance prediction, a new pavement performance prediction model was established based on the particle swarm optimization (PSO) algorithm and support vector machine regression (SVR) algorithm. First, the SVR algorithm was introduced into the model to deal with the nonlinear regression. Then the PSO algorithm was applied to improve the searching efficiency and parameter continuity of the SVR algorithm. The pavement inspection data of an expressway in eastern China from 2006 to 2015 were used to verify the results, proving the feasibility of the PSO-SVR prediction model. The research results show that the model using particle swarm optimization has a fast convergence speed, and the optimized support vector machine has better rutting prediction performance and perfect generalization, and the prediction accuracy and reliability are higher than those of unoptimized support vector machine model. [ABSTRACT FROM AUTHOR]

Here, we have prepared a novel mesoporous powder (CGSF3) from coal-gasification fine slag. The specific surface area and pore volume of CGSF3 were 564 m2 g−1 and 0.807 cm3 g−1, respectively. Furthermore, CGSF3 was introduced into polypropylene (PP) to prepare PP composites. When the filler content was 30 wt%, the tensile, impact, and flexural strengths of the PP-CGSF3 composite were 49.84%, 70.81%, and 139.63% higher than those of the conventional PP-CaCO 3 composites, respectively. More significantly, the total amount of volatile organic compounds (VOCs) volatilized from PP-CGSF3 was 67.6% less than that of neat PP, far exceeding the performance of zeolite deodorant filler. The strength of this work is that the high-performance and low-cost mesoporous resin fillers can be prepared from solid wastes. [Display omitted] • The solid pollutant coal gasification fine slag was reused reasonably. • Proposed an economic method for large-scale production of high efficiency and multifunctional mesoporous resin filler. • Prepared a mesoporous powder (CGSF3) with a specific surface area of 564 m2 g−1. • CGSF3 can significantly improve the mechanical strength of PP composites compared with the commercially available filler. • CGSF3 can greatly reduce the total VOCs volatilization of PP resin, down to 32.4%. [ABSTRACT FROM AUTHOR]

Summary: The ponding water and ice on the road surface can cause degradation of skid resistance that seriously affects driving safety. In order to accurately detect road surface conditions, an integrated photoelectric system was developed composed of an infrared light‐emitting diode and a phototransistor. Typical asphalt pavements such as AC‐13, SMA‐13, and OGFC‐13 were selected to simulate four road surface conditions: dry, wet, ponding water, and ice. The voltage intervals for dry and wet surface conditions were proposed by the light intensity method. The functional relationships were established between the depth of ponding and the output voltage, the thickness of ice, and the output voltage, respectively. The noncontact detection system for pavement ponding and freezing was developed by the design of the hardware of real‐time controller, the software of supervisory computer, and the shell of entire system. Then the system was verified in the field conditions. According to the test results, there was a good linear relationship between the ponding depth and the output voltage, while there was a quadratic parabolic relationship between the ice thickness and the output voltage. The detecting accuracy was 91.67% for the dry and wet surface conditions. The detecting errors of ponding depth for three different types of pavement surface were 0.248, 0.168, and 0.189, respectively; the detecting errors of the ice thickness for three different types of pavement surface were 0.219, 0.261, and 0.326, respectively. The errors were within a reasonable range, and the detecting accuracy of ponding depth is higher than that of ice thickness. [ABSTRACT FROM AUTHOR]

• TOPSIS model was applied to pavement preventive maintenance. • The interval-valued theory was applied to maintenance data. • Control indexes and functional indexes were established. • Network-level pavement evaluation system was proposed. The preventive maintenance (PM) comprehensive evaluation model is developed to find the optimal airport asphalt pavement PM project quickly, accurately and efficiently. By optimizing the TOPSIS method and introducing information entropy to determine the weights, the interference of subjective factors is avoided. Combined with the interval-valued theory, the interval-entropy weight-TOPSIS model is established to be more consistent with the needs of network-level PM. The model is successfully used to demonstrate the effectiveness and practicability at several airports in China. The obtained results show the optimal PM recommendation can be obtained by the model due to the consideration of more objectivity and practicality. [ABSTRACT FROM AUTHOR]

• A novel de-icing fiber permeable mixture (DFPM) is prepared. • The water permeability, road performance and de-icing performance of DFPM were evaluated. • A long-term performance test process was designed to predict the de-icing longevity of DFPM. • DFPM with 0.3% fiber and 5% de-icing agent shows superiority in performance and cost. The complex and changeable service conditions require pavements with greater functional diversity and environmental adaptability. In this paper, the de-icing fiber permeable asphalt mixture (DFPM) that satisfied the multiple service requirements of rapid drainage and ice melting in various seasons was proposed. Various performance characterization tests were utilized to evaluate the permeability and de-icing properties and the pavement performance of the mixtures with different contents of de-icing agents and fibers. Meanwhile, the high temperature dynamic water scouring experiment was designed to predict the effective de-icing life. The results show that adding de-icing agents and fibers slightly affects the water permeability of the mixtures. The incorporation of de-icing agents is beneficial to the high temperature performance yet detrimental to the low temperature behavior and water stability, while the incorporation of fibers compensates for the negative effect; the de-icing performance of the mixture correlates positively with the amounts of de-icing agents and correlates negligibly with the fiber incorporation. DFPM with 0.3% fibers and 5% de-icing agent shows superiority in performance and cost and is recommended for practical applications. Therefore, building a composite functional asphalt pavement with excellent performance appears feasible while creating a pavement micro-ecology by applying de-icing fibers permeable asphalt mixtures. [ABSTRACT FROM AUTHOR]

Introducing the crumb rubber into asphalt binder not only can improve the performances of asphalt binder significantly but also can recycle the waste tire economically. However, rubber asphalt presents different mechanical property for the complex sources of crumb rubber. In this study, rubber was classified according to the application situation and the components of tires and three kinds of rubber were selected as the representative of commonly used rubber. Afterwards, molecular dynamics simulations including molecular modelling, dynamics calculation, and mechanical properties analysis were conducted for rubber asphalt with the obtained rubber based on Materials Studio 8.0 software. The variation of mechanical properties of rubber asphalt with rubber contents and rubber types was investigated. The results show that the optimum rubber contents for the tire tread of passenger car, the tire tread of truck, and the tire sidewall are 15%, 5~10%, and 15% respectively. Moreover, rubber from the tire tread of passenger car and the tire sidewall should be given priority for actual applications in rubber asphalt. [ABSTRACT FROM AUTHOR]

Asphalt and filler interaction plays a key role on the performances of asphalt mastics and mixtures, while the asphalt and filler interaction ability is in turn affected by the material characteristics. In order to analyse the effects of material characteristics on asphalt and filler interaction, two kinds of matrix asphalt binders and three kinds of fillers were used to prepare asphalt mastics with different filler volume fractions. The dynamic shear rheological properties of these asphalt mastics were measured. The evaluation index K–B–G* was calculated subsequently to analyse the effects of material characteristics on the asphalt and filler interaction ability. The results show that filler volume fraction, filler particle size, SiO2 content and asphalt components had various levels of effects on the asphalt and filler interaction ability. Variance analysis was then conducted to rank these influencing factors from high to low as: (1) filler particle size, (2) asphaltene and resins content, (3) filler volume fraction, and (4) SiO2 content. [ABSTRACT FROM AUTHOR]

• The impact of asphalt components on the rheology of asphalt was explored. • The impact of asphalt components on the interface interaction was explored. • The impact of asphalt aging degree on rheology and interaction was analyzed. • The impact of filler characteristics on the interface interaction was studied. The strength of the interface between asphalt and filler is relatively low, making it susceptible to stress concentration and damage, which can affect the service life of the asphalt pavement. Current research indicates that there is a significant relationship between the interfacial interaction behavior and the properties of both asphalt and filler. Based on this, this study investigated the influence of both asphalt and filler properties on the interaction behavior of the asphalt-filler interface. Firstly, this study conducted research on existing interaction evaluation indicators and selected Palierne C as the optimal evaluation indicator for this study, which has the weakest correlation with filler volume fraction, in order to avoid the influence of filler volume fraction on experimental results. Secondly, this study analyzed the effects of asphalt SARA components and aging degree on the interface interaction ability between asphalt and fillers, as well as the rheological properties of asphalt. The research results found that the asphaltenes and resins fractions can enhance the interaction ability between asphalt and filler, as well as the high-temperature performance of asphalt. The content of these fractions was positively correlated with the interaction between the interfaces. In contrast, the content of aromatics and saturates fractions was negatively correlated with the interaction capacity. The strength of the interaction was negatively correlated with aging time, and long-term aging inhibited interface interaction to a greater extent than short-term aging. Finally, the mineral and chemical composition of common fillers were analyzed by X-ray diffraction (XRD) and X Ray Fluorescence (XRF). Subsequent studies were carried out on the interaction of the asphalt-filler interface in terms of the mineral composition, chemical composition, and particle size of the filler. It was found that in terms of mineral composition, albite and asphalt have the strongest ability to interact at the same temperature, followed by calcite and the weakest by quartz. In terms of chemical composition, the strongest interaction was between MgO and asphalt, followed by CaO, Fe 2 O 3 and Al 2 O 3 , and the interaction between SiO 2 and asphalt was the worst. In addition, the smaller the particle size of the filler, the greater the interaction capacity. [ABSTRACT FROM AUTHOR]

In this paper study, two kinds of self-healing microcapsules embedding waterborne epoxy resin (WER) and curing agent (CA) are synthesized by using the interfacial polymerization method, which could be incorporated into asphalt binders to prepare the novel self-healing materials and have the potential application to repair the micro-damage and micro-crack in asphalt materials. The two capsule-core materials were emulsified by using different emulsifier dosage and emulsification time, and the normal distribution characteristics of the particle size and quantity were statistically analyzed to determine the optimal emulsification solution. Then, ethylene glycol and toluene diisocyanate (TDI) were selected as the capsule-wall raw materials, and the microcapsules were prepared by using different core-wall materials ratio. The particle dispersion, surface morphology and coating properties were statistically analyzed to determine the optimal synthetization. FT-IR analysis results demonstrated that the microcapsules were successfully prepared by suing those optimized schemes. The optimal synthetization of WER microcapsules that 0.5% emulsifier dosage, emulsification for 16 min, core-wall materials ratio of 1.3:1, and the optimal synthetization of CA microcapsules is that 0.7% emulsifier dosage, emulsification for 16 min, core-wall materials ratio of 1:1. SEM and TG-DSC analysis results showed that the microcapsule particles were uniform, well-dispersed and regular in shape, and the capsule-wall thickness was about 1.0 μm. The thermal stability of the WER microcapsules is better than the CA microcapsules. [ABSTRACT FROM AUTHOR]

The silicon dioxide (SiO2) and calcium oxide (CaO) analytical reagents are selected to prepare asphalt mastics and the effects of aggregate chemical composition on asphalt-aggregate interactions (AAI) are evaluated based on the complex modulus and phase angle. It is found that the oxide analytical reagents significantly affect the rheological properties such as complex shear modulus and phase angle, and the effects of CaO are greater than SiO2 due to the stronger interaction between asphalt binder and CaO analytical reagents. Both the modulus stiffening ratio and the phase angle-based K. Ziegel-B coefficient could be used to evaluate the AAI, and the latter is the better index. Results show that the indexes increase with the test temperature, but decrease with the loading frequency, and tend to be constant. The higher adhesive strength between asphalt binder and limestone than basalt is likely attributed to the higher content of CaO in limestone aggregate and the stronger asphalt-CaO interaction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effects of various factors on asphalt-aggregate adhesive property were evaluated. • The pull-off test was improved to precisely control the asphalt film thickness. • SARA composition had the most significant effect on interfacial bond strength. • C value correlated significantly with bond strength of asphalt-aggregate interface. The performance of the asphalt binder-aggregate interface is an essential guarantee of the stability and durability of asphalt pavements. The objectives of this paper are to investigate the effects of various factors (test conditions, material properties) on the interfacial adhesive properties of asphalt binder-aggregate systems and to analyze the correlation between the bond strength and interface interaction. For this purpose, the improved pull-off tests under various temperatures, loading frequencies and asphalt film thickness were carried out to determine the test conditions for interfacial adhesion failure. The interfacial bond strength of various asphalt binders-aggregates and the corresponding interaction values were tested according to the determined test conditions and the correlation between them was analyzed. The results show that the bond strength between asphalt binder and aggregate was negatively correlated with temperature and positively correlated with loading rate, and there was an optimal film thickness. Among the selected minerals and aggregates, calcite and limestone presented the best bonding properties with asphalt binder respectively. Asphaltenes and resins enhanced the bond strength of asphalt binder-aggregate, while saturates and aromatics weakened the bond strength of asphalt binder-aggregate. The short-term aging of asphalt binder was beneficial to the bonding of binder and aggregate, whereas the long-term aging of asphalt binder was detrimental. Among the material properties factors, the SARA composition had the most significant effect on interfacial bond strength. A significant correlation was found between the C value (the preferred interaction parameter) and the bond strength of the asphalt binder-aggregate interface. [ABSTRACT FROM AUTHOR]

A reliable UMAT subroutine of selected constitutive model of asphalt mixture is developed and applied to characterize the three-stage rutting behavior of asphalt pavement by using ABAQUS. It is indicated that the heavier traffic load not only induces the greater rutting depth, but also accelerates the rutting rate, causing the pavement earlier enter into rutting failure with shortened service life. The damage evolution and axle-load conversion are further discussed. Results show that the pavement subjected to heavier axle loads has the greater damage and faster damage evolution. The axle-load conversion index is 5.97 according to rut equivalence principle. [ABSTRACT FROM AUTHOR]

The asphalt and filler interaction plays a significant role on the performances of asphalt mastics and mixtures, and the asphalt and filler interaction ability is affected by the temperature and loading frequency. In this paper, two kinds of matrix asphalt binders and three kinds of fillers were selected to prepare asphalt mastic with different filler volume fractions, and the dynamic shear rheological properties of asphalt mastics were measured. The linear viscoelastic range of matrix asphalt binder and mastic was analyzed firstly. Then the K-B-G ∗ model was used to evaluate and analyze the influence of temperature and loading frequency on asphalt and filler interaction ability. The results show that the linear viscoelastic range of matrix asphalt binders decreases with the loading frequency increasing and increases with the temperature increasing, the linear viscoelastic range of asphalt mastics decreases with the filler volume fraction increasing at the constant temperature and loading frequency. K-B-G ∗ exponentially increases with the temperature increasing and linearly decreases with the loading frequency increasing. The significance analysis of temperature and loading frequency was conducted by using grey correlated method, and finding that the temperature has deeper influence than loading frequency. [ABSTRACT FROM AUTHOR]

Semi-flexible pavement has been widely used for good performance, however, few studies have been made on effects of composition and formulation on grouting material. Therefore, this paper focuses on effects of composition and formulation on two typical grouting materials, including cement paste and cement mortar. The optimal formulations of these two materials are determined, and their performances are compared in terms of fluidity, strength and drying shrinkage. The result shows that fluidity, strength and drying shrinkage of cement paste and cement mortar vary with their composition, and both of the two materials can meet the technical requirements in the appropriate formulations. Comparatively, cement paste with its optimal formulation is more suitable as a grouting material for its better performance. The optimal ratio of water to cement is 0.58, the coal ash accounts for 10% and mineral powder accounts for 10%. [ABSTRACT FROM AUTHOR]

Modified Burgers model was applied to develop residual viscoelastic (RVE) and nonlinear viscous (NLV) strains for asphalt concrete subjected to repeated loading, and nonlinear viscoelastic damage (NLVED) model was then established and validated by incorporating damage variable. It is found that RVE strain proportion decreases with loading cycles and rest period, and NLV strain is predominant in total permanent strain. The repeated load permanent deformation (RLPD) test results show that the proposed NLVED model can well describe the three stage behavior of asphalt concrete in terms of permanent strain, strain rate and flow number. The damage evaluation shows that the damage of asphalt concrete is generated in the initial load and monotonically increases with the increasing loading cycles and becomes bigger and develops rapider at higher stress and temperature conditions. [ABSTRACT FROM AUTHOR]

In order to further broaden the application scope of basalt fiber reinforced concrete (BFRC), prolong service life in complex environment, master development status and sort out development needs, the durability of BFRC in complex environment was systematically summarized. First of all, the reason and damage mechanism of concrete deterioration in a variety of harsh environment are analyzed and grasped. Secondly, the strengthening mechanism of basalt fiber (BF) structure in permeability, carbonization, sulfate erosion, alkali environment, freeze-thaw cycle and high temperature is reviewed in detail, and the strengthening effect and performance of BFRC are discussed from the perspective of macroscopic properties and microscopic pore structure. The addition of BF reduces the generation and development of early microcracks in concrete structures, promotes the densification of structures on a microscopic scale. What's more, the permeability, carbonation resistance, acid and alkali corrosion resistance, frost resistance and high temperature resistance of concrete structures can be significantly improved. Finally, the problems in the current research are summarized and research ideas to cope with the environmental complexity are proposed to provide a research basis for BFRC to maintain excellent performance in the actual complex application scenarios. This paper focuses on the strengthening effect of basalt fiber on cement-based materials, and mainly introduces its strengthening effect and action mechanism from several aspects in the figure. [Display omitted] [ABSTRACT FROM AUTHOR]

Sasobit additives with different dosages were added into 70# and 90# virgin asphalt binders to prepare WMA binders. The rheological properties, including G∗ and δ, were measured by using DSR at the temperature ranging from 46°C to 70°C, and the effects of temperature, additive dosage and aging on G∗/sin⁡δ, critical temperature, and H-T PG were investigated. The results indicate that WMA additive improves G∗ but reduces δ, and the improvement on 70# virgin binder is more significant. G∗/sin⁡δ exponentially decreases with the increasing temperature but linearly increases with the increasing additive dosage. Aging effect weakens the interaction between binder and additive but significantly increases the binder’s viscosity; that is why G∗/sin⁡δ is higher after short-term aging. In addition, the critical temperature increases with the increasing additive dosage, and the additive dosage should be more than 3% and 5% to improve H-T PG by one grade for 70# and 90# virgin binder, respectively. [ABSTRACT FROM AUTHOR]

Two matrix asphalt binders are used to prepare warm mix asphalt (WMA) binders with different dosages of Sasobit® additive, and the general technical properties, the dynamic viscosities at 60 °C, the apparent viscosities above 110 °C are measured and analyzed. It is found that the apparent viscosity exponentially decreases with the increase in temperature and could be considered as independent on shear rate. The dynamic viscosity exponentially increases with the increase in additive dosage, but the apparent viscosity linearly decreases. The WMA binder with more additives is more temperature susceptive, and the different effects of the additive on the viscosity-temperature characteristics is mainly because of the temperature transition point of the additive around 100–110 °C. The additive improves both the high temperature property in serve stage and workability during construction. However, it worsens the low temperature property, which should be paid more attentions in practice. [ABSTRACT FROM AUTHOR]

Permanent deformation of asphalt mixture under repeated load can be divided into three phases: decelerating phase, stationary phase, and accelerating flow phase. Most of the existing models cannot fully describe deformation characteristics during the three phases. In this paper, the characteristics of three-phase permanent deformation are considered as the results of a competition between damage and hardening, in which a damage variable and a hardening variable are introduced to modify Burger's model. First, the series-wound dashpot of the Burger's model is modified by Usan's hardening variable, and the undamaged viscoelastic properties are derived from rheological theory. Secondly, Kachanov's equation for damage evolution is adopted to establish the constitutive model by using Lemaitre's effective stress principle. Then a repeated load consisting of a haversine loading period and rest period is employed to simulate the actual vehicle loading on the asphalt pavement. Third, a viscoelastic-damage mechanical model is proposed to characterize the permanent deformation of asphalt mixture under repeated load. The proposed model is validated by conducting uniaxial permanent deformation tests on four kinds of asphalt mixtures. The model parameters are obtained by using the principle of least square. The proposed model is capable of describing the whole three-phase permanent deformation of the asphalt mixtures. The proportion of residual viscoelastic strain to permanent strain decreases very quickly as load cycle increases and only accounts for during most of the loading period. It is indicated that residual viscoelastic strain is significantly less than the permanent strain, thus the residual viscoelastic strain can be ignored and the proposed model could be simplified to a concise format. [ABSTRACT FROM AUTHOR]

[Display omitted] • Different rubber-aggregate combinations present the different friction performance. • Velocities significantly influence friction by changing average longitudinal stress. • Temperatures slightly influence friction by changing average vertical stress. In order to clear the relationships between materials genes of tire-pavement and their friction performance, the confined shear simulation was conducted to simulate the friction process between tire rubber and aggregates by using MD simulation. Moreover, the effects of velocity and temperature on friction were also investigated. The results showed that different rubber-aggregate combinations present the different friction performance. Generally, the friction is the relatively largest for the aggregate-SBR-aggregate layers compared to BR and NR related layers. By comparison, the friction between calcite and rubber is the smallest, while the friction between microcline and rubber is the largest. The velocities will influence the friction behavior between quartz and rubber. The coefficient of friction will increase firstly and decrease then with the increase of the shear velocity. The variation of coefficient of friction with the velocity can be attributed to the change of the average longitudinal stress during the friction process. The coefficient of friction for NR-quartz and BR-quartz is slightly influenced by the temperatures, while it is significantly influenced for SBR-quartz. The variations of coefficient of friction with the temperature are mainly dominated by the average vertical stress. [ABSTRACT FROM AUTHOR]

[Display omitted] • Effects of asphalt emulsion on the durability properties of SCC. • The microscopic mechanism of SCC modified by asphalt emulsion. • The durability properties of SCC modified by asphalt emulsion is good. • The asphalt emulsion with the content of 10 wt% give the most desirable effect. Asphalt emulsion (AE) is the alternative raw material for self-compacting concrete (SCC), some researchers have reported on the composition design, workability, and strength properties recently. But few attempts have be made on the durability. For a better understanding on the effects of AE on SCC durability and its microscopic mechanism, the SCC specimens were prepared with various AE contents, and the self-compacting workability was confirmed via slump flow test. Then, three kinds of durability tests were performed to evaluate the chloride-penetration resistance, frost resistance and sulfate-corrosion resistance, and the scan electronic microscope (SEM) test and X-ray diffraction (XRD) test were performed to discuss the microscopic mechanism. The results show that the chloride-penetration resistance, frost resistance and sulfate-corrosion resistance of SCC were enhanced by adding AE. Observed from SEM test, the interfacial transition zone (ITZ) of SCC is mainly filled with the C-S-H gel and AE, and the SCC microstructure tends to be compact, resulting that the concrete durability was improved by using appropriate AE. However, the excessive AE may lead to more pores in SCC because of the retardation effect on cement hydration. The AE with the content of 10% given the most desirable effect for durability. [ABSTRACT FROM AUTHOR]

In this project, the adhesion property and moisture effect between styrene–butadiene–styrene (SBS) modified asphalt binder and aggregate were studied to reveal their interface adhesion mechanism. The influence of SBS contents on adhesion property and moisture effect between binder and aggregate phases were investigated using molecular dynamics simulation. Moreover, the double-layer adhesion models of asphalt binder–aggregate and triple-layer debonding models of asphalt binder–water–aggregate were constructed and equilibrated, and the adhesion property and the moisture effect were evaluated numerically. The results indicate that the built SBS-modified asphalt binder models show favorable reliability in representing the real one. The variation in the work of adhesion for SBS modified asphalt binder–quartz is not remarkable with the SBS content when its content is relatively low. However, the work of adhesion decreased significantly when the content was higher than 6 wt.%, which is consistent with the experimental results. The adhesion between SBS-modified asphalt binder and quartz is derived from Van der Waals energy. The modified asphalt binder with a high SBS modifier content (8 wt.% and 10 wt.%) shows much better moisture resistance (nearly 30% improved) than the unmodified asphalt binder from the work of debonding results. According to the Energy Ratio (ER) values, asphalt binders with high SBS content (8 wt.% and 10 wt.%) present a good moisture resistance performance. Therefore, the SBS content should be seriously selected by considering the dry and wet conditions that are used to balance the adhesion property and debonding properties. The content of 4 wt.% may be the optimal content under the dry adhesion and moisture resistance. [ABSTRACT FROM AUTHOR]

In this study, a 5:1 rectangular section was taken as the research object. An aerodynamic reduced-order model was used to verify whether the rectangular section had a similar oscillation mechanism to a circular section based on the results of two-dimensional unsteady Reynolds-averaged Navier–Stokes calculations. Computational fluid dynamics was used to study the vertical oscillation characteristics of the 5:1 rectangular section under the influence of different parameters. The results showed that the vertical oscillation of the rectangular section could be divided into two patterns according to the oscillation characteristics: "resonance-induced vibration" and "competition-induced vibration." The resonance-induced vibration shows a quick development in amplitude, while competition-induced vibration has two stages before stabilization. The vibration amplitude, oscillation frequency, and lock-in region were affected by variations in the mass ratio. The damping ratio had less effect on the oscillation frequency and vibration amplitude than the mass ratio. However, a reduction in the damping ratio enlarged the lock-in region at a high reduced velocity. Additionally, the difference in the initial displacement had a considerable influence on the vibration amplitude of competition-induced vibration, while it had little effect on resonance-induced vibration. [ABSTRACT FROM AUTHOR]

• Influences of preparation process on bio-binders performance is studied. • Three preparation methods about swine manure bio-oil binder were proposed. • Swine manure bio-oil can reduce the viscosity of binder and improve the workability. • Premix bio-oil and rubber powder can reduce the bad effects on asphalt performance. Millions of tons of waste glass are produced every year and its management is one of the biggest environmental problems. In other hands, there is a need to discover potential light-transmitting layer for the future photovoltaic road. The purpose of this research is to assess the feasibility of waste tempered glass (WTG) as the aggregates in light-transmitting concrete. Light-transmitting concrete (LTC) specimens were prepared by penetration method with different proportions of waste tempered glass aggregates and epoxy resin binder. Four grading types were selected preliminarily to determine the resin content and curing age. The WTG particle distribution was tested, as well as the optimal gradation was determined according to the light transmittance test and compressive strength test. The results show that the light transmittance of LTC is related to the WTG particle size and gradation. The larger the particle size, the higher the light transmittance, while, the denser the gradation, the lower the light transmittance. There are two main factors affecting the compressive strength, including the amount of cement and the degree of embedding between aggregates. Since the penetration method is applied to mold the specimens, the bonding between binder and the aggregate plays a major role. The smaller the particle size, the larger the specific surface area, and the more contact with the binder, the higher the strength. By comprehensively comparing the two indexes of light transmittance and compressive strength as well as the utilization ratio of glass, the GOGFC-13 was determined as the optimal gradation. Further, the design process of LTC was summarized with a view to have the potential application values for the future photovoltaic road. [ABSTRACT FROM AUTHOR]

• Waste glass can be reused as glass aggregates to replace part of mineral aggregates. • The replacement of glass aggregates is negative to the performances of the mixtures. • Nano-Fe 2 O 3 can improve the viscosity between glass aggregates and asphalt materials. • The application of waste glass can significantly improve the surface luminance. In this paper, based on the concept of water glass recovery and sponge city, the waste glass was applied as part of aggregate to prepare a kind of porous glasphalt mixtures. The glass cullet was crushed to a certain size as glass aggregates to partially replace the mineral aggregates. The performances of glasphalt mixtures were tested and evaluated. In the experiment, four groups are designed, which are ordinary asphalt mixtures, cement-modified asphalt mixtures, glasphalt mixtures with no surface-treated glass, and glasphalt mixtures with surface-treated glass. Through the tests of road performance, the No. 4 group of glasphalt mixtures with 84% mineral aggregate + 1% Portland cement + 15% glass aggregates treated by Fe 2 O 3 suspension has good technical properties in high temperature stability, low temperature stability, and water stability, although slightly poorer than that of asphalt mixtures. As the glasphalt mixtures are for the porous asphalt pavement, the volume of connected air voids and permeability coefficient was calculated. In addition, the method of MATLAB grayscale image processing is used to evaluate the reflective property of glasphalt mixtures, and it is found that the application of glass can significantly improve the surface luminance. This environmentally friendly glasphalt mixtures not only solve the problem of environmental pollution caused by waste glass but also saves the cost of pavement materials, improves the road traffic environment visibility. Therefore, the new type of glass asphalt pavement has good economic and social benefits, and it is worth to be promoted. [ABSTRACT FROM AUTHOR]

• Proposed a economic method for large-scale production of sorbents for capture CO 2. • Prepared a mesoporous material (labeled as FSA) with a specific surface area of 541 m2 g−1. • The maximum adsorption capacity of amine functionalized FSA (named asFSA-TEPA-20) for CO 2 was 132.5 mg g−1 at 273 K. • FSA-TEPA-20 shows a higher partition coefficient value compared with other mesoporous materials. • FSA-TEPA-20 has good thermostability and regenerability. Here, a novel adsorbent was prepared from coal-gasification fine slag by acid leaching and amine modification and was used for CO 2 capture. The fine slag adsorbent (FSA) material was found to have a specific surface area of 541 m2 g−1 and a pore volume of 0.543 cm3 g−1. To improve the CO 2 adsorption capacity of the material, the raw FSA was immobilized with amines through physical impregnation. The FSA-based composites were developed using four types of amines: ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), and tetraethylenepentamine (TEPA). The optimum formula was found to be the FSA loaded with 20 wt% TEPA (FSA-TEPA-20), whose theoretical maximum adsorption capacity for CO 2 was 132.5 mg g−1 (273 K). The partition coefficient values obtained at 100% breakthrough for FSA and FSA-TEPA-20 were determined as 1.4 × 10−4 and 3.3 × 10−4 mol kg−1 Pa−1, respectively, which were far superior to those of other mesoporous materials (e.g., SBA-PEI). The FSA-TEPA-20 showed good cycling stability. The reaction mechanism was investigated, and the thermodynamic/kinetic parameters for CO 2 adsorption were derived; the adsorption was demonstrated to follow the Avrami model. The strength of the preparation strategy is it enables the development of a high-performance adsorbent from low-cost solid wastes. [ABSTRACT FROM AUTHOR]

Infrared spectrum of the B-type microcapsule. The material composition of the prepared microcapsules was analyzed using Fourier Transform Infrared Spectroscopy (FT-IR), and the microcapsules were successfully prepared by analyzing the absorption characteristics in infrared radiation of different wavelengths. The a, b, and c represent the spectra of the core material, the wall material, and the microcapsules, respectively. • The microcapsules dispersed uniformly in the crack sealant. • Both microcapsules have the same probability of being destroyed. • The thermal stability of the microcapsules meets the construction requirements. • One hour of rest time is too short and curing takes longer. In order to improve the repeated repair ability of asphalt-based crack sealants, two types of microcapsules were prepared and added into asphalt-based crack sealant. The epoxy resin and curing agent were microencapsulated by using interfacial polymerization method, and named as A-type and B-type microcapsules respectively. The effects of emulsifier content and core-wall ratio on the preparation of two types of microcapsules were analyzed, and SEM, FT-IR, TG-DSC, and FOM analyses were performed to study the microscopic features of microcapsules, including the particle size and size distribution, chemical components, morphological features, thermal stability as well as the dispersion of microcapsules in the sealant. Then, DSR tests were conducted with two-stage loading mode to evaluate the repeated repair ability of asphalt-based crack sealants with different dosages of microencapsulated epoxy resin and curing agent. The results show that the optimal emulsifier contents are 0.5% and 0.7% for the A-type and B-type microcapsules respectively, and the corresponding core-wall ratios are 1.3:1 and 1.1:1 respectively. The two types of microcapsules were successfully prepared with well-distributed particle sizes and sufficient thermal stability, which are be well dispersed in asphalt-based sealants. The repeated repair ability indexes were proposed based on DSR complex shear modulus and the corresponding loadings cycles. It is found that the repeated repair ability of composited sealants is obviously improved. The optimal dosage of two types of microcapsules are 3%, and a sufficient healing time is required for repairing crack due to the indispensable curing process of epoxy. [ABSTRACT FROM AUTHOR]

• Microcapsules containing sunflower oil are prepared successfully. • Microcapsules did not affect the traditional properties of bitumen-based sealant. • Microcapsules improve obviously low-temperature tensile property of bitumen-based sealant. • Microcapsules improve obviously self-healing property of bitumen-based sealant. The bitumen-based sealants have been widely used to repair the pavement cracks, but the pavements always crack again at the healing patches due to the insufficient durability of sealants. In order to improve the technical properties and self-healing ability of bitumen-based sealants, the microcapsule technology was applied, and the sunflower-oil microcapsules were prepared by in-situ polymerization method. The sunflower-oil microcapsules were then added into the bitumen-based sealants, and the dispersion characteristic was observed by fluorescence microscopy, Then the cone penetration, softening point, resilience recovery, fluidity, tensile property sealants, self-healing ability as well as the two-stage loading dynamic shear rheological (DSR) tests were conducted to study conventional technical properties and the self-healing ability of bitumen-based sealants containing microcapsules with different contents. The results show that microcapsules could be well dispersed in the sealants state without agglomeration, and the conventional properties of bitumen-based sealants containing microcapsules meet the technical requirements, except for low-temperature tensile properties of the sealant with 4% microcapsules. The cone penetration and fluidity decrease with increasing microcapsule content, while the softening point and resilience recovery increase. Compared with the original sealants, the self-healing ability of the sealants with microcapsules was superiority obviously, and the optimum content of microcapsules was recommended as 2%, which was also suitable for the aged sealants. And the sunflower-oil microcapsules can improve the repeated self-healing ability and fatigue life of the sealants at the temperature as low as −20 °C. [ABSTRACT FROM AUTHOR]

• Radial distribution function can evaluate interaction behavior of rubber asphalt. • Agglomeration of rubber-asphalt is more obvious than inter-components of asphalt. • Adsorption of rubber to asphalt follows this order: BR > SBR > NR. • Agglomeration of rubber asphalt is more clustered for more light fractions asphalt. In order to clear the interaction mechanism between rubber and asphalt binder in rubber asphalt, radial distribution function was selected to investigate the variation of the agglomeration of rubber asphalt with rubber and asphalt binder types, where molecular models of rubber asphalt were built firstly, molecular dynamics simulations were performed afterwards and the variation of agglomeration behavior and adsorption effect were analyzed finally based on Materials Studio 8.0. The results show that the agglomeration of asphalt binder is changed significantly with the addition of rubber. The agglomerations of rubber-naphthene aromatic and rubber-saturate is more clustered than that of asphaltene-naphthene aromatic and asphaltene-saturate, and the agglomeration of rubber-naphthene aromatic is more clustered than that of rubber-saturate. The adsorption of different rubber types to light fractions of asphalt binder follows this order: cis-polybutadiene rubber (BR) > styrene butadiene rubber (SBR) > natural rubber (NR). In addition, the more clustered agglomeration structure of rubber-asphalt will be formed with the higher proportion of naphthene aromatic and saturate in asphalt binder. [ABSTRACT FROM AUTHOR]

• The applications of FTIR in asphalt materials research are reviewed. • The mechanisms of different ageing method are discussed from FTIR perspective. • The performance prediction models based on FTIR and chemometrics is discussed. • Multispectral data fusion approach is envisaged for future research. Fourier-transform infrared spectroscopy (FTIR) has become a crucial method for both qualitative and quantitative analysis in characterizing asphalt materials. The present work aims to provide a comprehensive review of recent uses of FTIR in this field, that ranged from material quality control, material identification, to the analysis of modification mechanism, including ageing mechanisms, as well as for macroscopic performance prediction. The narrative unfolds within a broader context, with the basic principles, and insightful comparisons with ultraviolet–visible (UV–vis) spectroscopy, Raman spectroscopy, and fluorescence spectroscopy. The instrumentations employed in FTIR research are inspected in detail, delving into testing modes, sample preparation, and data analysis methods, with a particular emphasis on its ability to identify asphalt components at the molecular level. Furthermore, FTIR analysis provides useful indications for various applications: i) quality identification; ii) asphalt materials modifications and ageing states identification according to molecular changes; iii) prediction for the physical and rheological properties of asphalt binder based on chemometric method. The prospects in asphalt research are proposed stressing the relevance of combining FTIR analysis to high-throughput experimental methods and other spectroscopy technologies, and coupling to machine learning (ML) methods. This paper provides a reference for researchers who intend to explore the quality control and to analyze asphalt binders from a microscale perspective, fostering further research on relationships between microscopic compositions and macroscopic properties. [ABSTRACT FROM AUTHOR]

• Proposed a cheap method for large-scale production of resin deodorant. • Prepared deodorant (FSD) with specific surface area of 393 m2 g−1. • Propane maximum adsorption capacity of 121.61 mg g−1. • FSD can significantly reduce the total amount of VOCs in PP resin, down to 50%. • FSD make up for the vacancy of efficient resin deodorants on the market. Deodorizing materials are often restricted from large-scale industrial production due to the high preparation cost. By utilizing the simple acid leaching technology, this study made use of the coal gasification fine slag (FS) as raw material to prepare a cost effective FS-based deodorant (FSD) with a specific surface area of 393 m2 g−1 and a pore volume of 0.405 cm3 g−1. The propane adsorption test on FSD showed the maximum adsorption capacity to be as high as 121.61 mg g−1 at 273 K. The partition coefficient values at 10% and 100% breakthrough (BT) for FSD to adsorb propane were 1.5 × 10−3 and 3.2 × 10−4 mol kg−1 Pa−1, respectively. Furthermore, the FSD was applied in the removal of volatile organic compounds (VOCs) pollutants from polypropylene resin (PP). It showed that the deodorizing effect of the FSD was nearly three times as good as the commonly used zeolite deodorants, which was able to decrease 50 percent of the VOCs volatilization amount in PP resin. Moreover, the FSD can better strengthen the mechanical properties of PP resin. This work provides a new method for the industrial production of deodorants as well as a new direction for the recycle of coal gasification wastes. [ABSTRACT FROM AUTHOR]

This paper summarizes the important research results of self-healing technology of asphalt materials, analyzes the healing mechanism of self-healing technology, and emphatically introduces the research status, advantages and disadvantages of five advanced self-healing technologies: Electromagnetic induction heating (EIH) technology, Microwave induction heating (MIH) technology, Photorepair method, Microcapsule method, and Hollow fiber (HF) method. The results showed that the existing self-healing mechanism is mainly based on surface energy theory, molecular diffusion theory and capillary flow theory, which explains the self-healing phenomenon of asphalt from different scales. The existing self-healing technology has developed rapidly, and the indoor research proves that the potential of MIH technology is higher than that of EIH technology. The repair potential of HF method is higher than that of microcapsule technology, but its material synthesis is more complicated. Photorepair technology has the potential to cooperate with other technologies, and it needs to be reasonably matched and selected. At the same time, the progress of related self-healing construction machinery and technology may require the continuous efforts of researchers. In addition, the organic synergy between different self-healing technologies may be a feasible way for self-healing technology to move from experimental section to practical application. In the future, a set of self-healing system with strong repair effect, environmental friendliness and reasonable cost can be established from the organic synergy of various self-healing technologies, combined with life cycle cost and intelligent sensors. • The existing mechanism explains the self-healing of asphalt from different angles. • The uneven heating of the induction heating technology still exists. • Photorepair method has the potential to combine with other technologies. • Relevant standards of self-healing technology need to be established. [ABSTRACT FROM AUTHOR]

Emulsified asphalt cold recycled technology has received great attention for its low carbon and environmental protection. There have been many researches on the performance improvement of emulsified asphalt cold recycling mixture (CRME) and its achievements, but there lacks systematic sorting. Based on this, this study summarizes the related research from the performance formation mechanism and influencing factors. Firstly, the demulsification mechanism of emulsified asphalt and the performance formation mechanism of CRME are summarized. Secondly, the influence of asphalt material (type and content), aggregate type (new aggregate, RAP), gradation, additives (regenerant, cement, fiber, etc.), water consumption and fabrication methods on CRME performance is analyzed. Finally, the future development of CRME is prospected. In the future, the fusion characteristics of old and new asphalt on RAP surface can be studied from multi-scale perspective. Besides, we can combine genome to construct CRME material library and improve the preparation technology standard of CRME pavement. • The development status of emulsified asphalt cold recycling technology was reviewed. • The influence of different factors on the strength of recycled mixture was analyzed. • The optimal dosage range of different influencing factors was summarized. • The development of emulsified asphalt cold recycling technology was prospected. [ABSTRACT FROM AUTHOR]

The high cost and high dosage of polyurethane (PU) used in asphalt modification limit its application in asphalt pavement construction. To address these problems, two novel PUs were synthesized by the reaction of low-cost polypropylene glycol (PPG-2000) separately with 4,4 - diphenylmethane diisocyanate (MDI) and with toluene diisocyanate (TDI). This study has further optimized the preparation process and analyzed the influence of the PU synthesis materials on the modified asphalt. Dynamic shear rheology, multiple-stress creep recovery, Fourier-transform infrared spectroscopy, and fluorescence microscopy were used to evaluate the rheological properties and aging resistance of modified asphalt. Results show that the PUs synthesized by MDI and TDI significantly improved the high-temperature performance, low-temperature performance, and aging resistance of modified asphalt compared to unmodified asphalt. Asphalt modified with the PU synthesized by MDI had better high-temperature performance, but the low-temperature performance and aging resistance were worse than those for asphalt modified with the PU synthesized by TDI. The results of rheological aging and chemical aging evaluation showed that the PU synthesized by TDI provided better anti-aging performance. The optimum dosages of both PUs were not more than 6%. These PUs reduce the cost of construction engineering and show excellent application prospects in pavement construction. These two PU-modified asphalts can be applied to pavement construction in different regions based on the properties required. • Low-cost and environmental TPU and MPU modified asphalt are prepared. • Optimal dosages of MPU and TPU for asphalt modification are lower than 6%. • The types of polyurethane have a significant impact on the performance of PUMA. • MPUMA and TPUMA are suitable for road in hot and cold region, respectively. [ABSTRACT FROM AUTHOR]

• Airport pavement preventive maintenance three-level evaluation index system is established. • PM decisions are considered as the binary classification problem. • The asphalt pavement decay model is developed based on PCI. • Project-level asphalt pavement PM timing was determined through confusion matrix. Accurate evaluation of the performance of airport pavement can help managers make scientific and systematic preventive maintenance (PM) decisions, ensuring pavement safety and extending service life. To this end, firstly, this paper sorted out the pavement performance evaluation index system, based on which a multi-dimensional evaluation system for PM was proposed, including control indexes, macroscopic indexes, and microscopic indexes. Then, the pavement decay model based on the pavement condition index (PCI) was developed, and the regression model between PCI and International roughness index (IRI) and friction coefficient (μ) was established. Finally, by converting the PM decisions for project-level pavement into a binary classification problem in machine learning, the optimal maintenance thresholds and intervals for PM of each index were determined using receiver operating characteristic (ROC) curve and Kolmogorov-Smirnov (K-S) curve. The optimal threshold represents the threshold when the index can separate the binary classification problem (PM decisions) with maximum probability. Based on confusion-regression model, the pavement performance can be evaluated more comprehensively, and the timing of PM can be accurately determined. The model helps airport managers develop accurate PM plans to address future maintenance needs. [ABSTRACT FROM AUTHOR]

Crumb rubber (CR), as a recycled rubber product manufactured from scrape tires, has been diffusely applied in asphalt binder for modification due to the environment benefit and performance improvement. To improve the content of CR and maintain the road performance of asphalts, CR was first treated with waste oil and then activated using microwave, named as waste oil pre-expanded and microwave activated CR (PMACR). Subsequently, the high-content (50–70%) PMACR-modified asphalts were prepared using terminal blend (TB) process. The components and microtopography of three CRs were investigated by Fourier Transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) tests. The rheological properties, high- and low-temperature performances, fatigue resistance, cohesion characteristic, storage stability of asphalts with various PMACR contents were examined. The results demonstrate that the high-content PMACR-modified asphalts are successfully manufactured in the laboratory, in which the PMACR content is approximately 70% by weight of matrix asphalt. With the increase of PMACR, the high- and low-temperature performance, fatigue resistance of TB PMACR-modified asphalts are greatly improved. When the content is up to 60%, the softening point difference of top and bottom of asphalt is less than 2.5 °C and the viscosity value of less than 2.5 Pa·s at 180 °C, which indicates high-content PMACR-modified asphalts pose sound compatibility and workability. [ABSTRACT FROM AUTHOR]

Three digital specimens of asphalt mixtures (AC-13, SMA-13 and OGFC-13) were reconstructed to conduct a virtual simple performance test using the discrete element method. The distribution characteristics of force chains were investigated by a statistical method. The results indicate that it is reasonable and feasible to analyze the mesoscopic responses of asphalt mixtures using digital models. The probability distribution of the normal force chains varies with loading time and the variation laws are consistent at four loading times. And the probability distribution of the shear force chains decays exponentially. Besides, the maximum probability distributions of the normal and shear force chains decrease with increasing timestep. OGFC-13 has the maximum probability distributions of the normal and shear force chains, which are 0.34186 and 0.55884, respectively. The proportions of the “strong” force chains decrease over the loading time, and AC-13 has a maximum proportion of 49.41% for the three asphalt mixtures at four loading times. In addition, the angle distributions of the force chain are mainly near 90°, and the average ratio of the normal contact force to the mean normal contact force increases with increasing loading time at 90°. Finally, the angle distribution proportions in the first and second quadrants are much greater than those in the third and fourth quadrants. [ABSTRACT FROM AUTHOR]

For the better understanding of fracture test method to evaluate the crack resistance of asphalt mixtures, the current test methods and evaluation indexes were theoretically and experimentally compared, including the indirect tensile test, single edge notch beam test, semicircular bending test (SCB) and disk-shaped compact tension test. The stress intensity factors for different tests were compared, and the appropriate range of notch depth was determined. The SCB was finally selected as the test method for evaluating the crack resistance of the asphalt mixtures. According to the relationship between the fracture energy and notch depths, the essential fracture energy of asphalt mixtures was calculated, and it was recommended as the evaluation index of asphalt mixtures for crack resistance. Furthermore, the failure process of the SCB was analyzed, and the contraflexure point on the load–displacement curve was found and defined. The fracture energy at the contraflexure point could be used to evaluate the ultimate crack resistance of the asphalt mixtures. The application of the essential fracture energy and the contraflexure point can correspond to the actuality of the asphalt pavement, which provides a reference for the crack resistance research of asphalt mixtures in the future. [ABSTRACT FROM AUTHOR]

• Self-developed LTTT can evaluate the low-temperature performance of sealants. • The surface roughness and adhesion of sealants are closely related to R value. • Roughness will affect the chemical bonding characteristics between sealants and SiO 2. • PCA method can comprehensively evaluate the macro–micro properties of sealants. In order to establish a comprehensive evaluation system of ballastless-track sealants, a method is put forward based on macro–micro tests and principal component analysis(PCA). In this study, the performance parameters of four different ballastless-track sealants (SE, NI, WQ, SY) were obtained by low-temperature performance test, atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS) test. Then the PCA method was conducted to reveal the complex relationship between macro and micro performance parameters of sealants, such as the maximum tensile force, the maximum failure displacement, the surface roughness, the surface adhesion, the chemical bonding rate with SiO 2 , and the principal component contribution rate was calculated. Finally, the comprehensive score was utilized to evaluate the performance of different sealants. The results show that the macroscopic properties of the sealant are closely related to the microscopic parameters roughness, surface adhesion and chemical bonding rate of SiO 2. The macro–micro performance parameters of sealant are comprehensively evaluated through PCA, and the results are as follows: NI > SE > WQ > SY. The PCA can comprehensively evaluate the performance of sealant intuitively and accurately, avoiding the subjective influence of evaluating the material performance only through macro-tests or micro-tests. [ABSTRACT FROM AUTHOR]

In this study, the rheological properties and adhesion characteristics of foamed CRA binder were studied. Firstly, the optimum foaming conditions of foamed CRA binder with different crumb rubber powder (CRP) content and foaming agent were studied. Secondly, stress creep recovery (MSCR) test, temperature scanning and frequency scanning tests were carried out by using dynamic shear rheometer (DSR), and the high temperature performance, temperature sensitivity and viscoelastic characteristics of each asphalt binder sample before and after aging were studied. Finally, the surface free energy theory was used to evaluate the adhesion characteristics of each sample. The results showed that the commonly used foaming agent cetyl trimethyl ammonium bromide has no effect on the foaming of CRA binder. With the increase of CRP content, the foaming temperature became higher, and it was difficult to foam successfully when the rubber powder content was higher than 15%. Increasing the content of CRP in a certain range can improve the high temperature performance and adhesion of foamed CRA binder and reduce its temperature sensitivity. With the aging process of the sample, the high temperature performance of foamed CRA binder increased, and the temperature sensitivity and adhesion characteristics decreased. The surface free energy of foamed CRA binder is mainly composed of dispersion component, and the polarity component is relatively small. The surface free energy of foamed CRA binder increased with the increase of CRP content. In addition, foaming agent B (water-in-oil emulsifier) would reduce the temperature sensitivity and high-temperature performance of foamed CRA binder, but it had no obvious effect on adhesion. • Optimal foaming conditions for rubber asphalt are discussed and the commonly used cetyltrimethylammonium bromide does not enhance its foaming effect. • The amount of crumb rubber powder used has an effect on the rheological properties of the foamed crumb rubber asphalt binder. • Aging reduces the surface free energy of the foamed rubber asphalt binder and reduces its adhesion properties. • The amount of crumb rubber powder mixed affects the surface free energy of the foamed crumb rubber asphalt binder. [ABSTRACT FROM AUTHOR]

[Display omitted] • As the airport's operating time increase, different types of pavement distress gradually appear, affecting the normal operation of the airport. • An improved Apriori algorithm was used to explore the evolution mechanism between typical distress. • The key to extending the service life of asphalt pavement lies in delaying and stopping the process of distress evolution. • Four microscopic evaluation indexes of pavement condition based on preventive maintenance are proposed. In order to better investigate the relationship between airfield asphalt pavement distress, 500 units of asphalt runway data were obtained from a scientific pavement zoning method for five airports, based on an extensive collection and survey of asphalt pavement distress types and damage levels. An improved Apriori algorithm was used to explore the evolution mechanism between typical distress, to establish a pavement evolution model and to characterize the distress deterioration probability by defining the deterioration degree. The data mining results show that there are three stages of asphalt pavement distress evolution, and that each distress can evolve from the previous distress. The key to extending the service life of asphalt pavement lies in delaying and stopping the process of distress evolution and accurately judging the key points of distress evolution from the perspective of pavement maintenance plans for the whole life cycle of pavement, which provides a scientific basis for further management of a preventive maintenance evaluation index system for asphalt pavements. [ABSTRACT FROM AUTHOR]

Semi-rigid base materials are used in all pavement grades and are shown to have excellent stability. Furthermore, semi-rigid bases are known for their stiffness and strong frost resistance. However, these semi-rigid base materials are starting to require significant levels of maintenance and repair due to wear and tear. Maintenance is performed primarily to add pavement and resurfacing material, with the hope that the resurfacing layer can withstand large tensile and shear forces at the cracks of the base, thus increasing the overall durability of the pavement. Furthermore, crushing technology used for cement panel maintenance can be used to eliminate cracks in the overlay layer thus improving overall service life expectancy. The studies below study the application of crushing technology to a semi-rigid base and the subsequent alternation to the structural design of the pavement. Furthermore, the mechanical index sensitivities of pavement structures post-rubblization were analyzed using finite elements. Mechanical indexes with high sensitivity were subsequently adopted as structural damage control indexes. These indexes were used to optimize overlay structure and provide a reference for structural design post-rubblization. [ABSTRACT FROM AUTHOR]

The rutting performance of asphalt pavement structure relies on the high temperature properties of asphalt mixture as well as the pavement structure and thickness. In order to investigate the influence of the structure and thickness, a full-depth wheel tracking test is developed in this research by improving the conventional wheel tracking test apparatus. The newly proposed test method is capable of varying its load speed and load size, controlling its specimen temperature gradient, and simulating the support conditions of actual asphalt pavement. The full-depth wheel tracking test based rutting performance evaluation of different asphalt pavement structures indicates that it is not reasonable to explain the rutting performance of asphalt pavement structure from the point of view of single-layer asphalt mixture rutting performance. The developed full-depth wheel tracking test can be used to distinguish rutting performance of different asphalt pavement structures, and two of five typical asphalt pavement structures commonly used in Shanxi Province were suggested for use in practical engineering. [ABSTRACT FROM AUTHOR]

To study the influence of aggregates geometrical features on the rheological properties of asphalt mixtures during compaction and service stage, asphalt mixtures with partially substituted aggregates were compacted by Superpave gyratory compaction (SGC), and their properties in service were measured by creep and dynamical modulus tests. The relation between rheological properties of mixtures and aggregate geometrical features was studied by gray relational analysis method. Results show that the rheological properties of mixtures during compaction and service stage are more sensitive to sieving diameter and shape index, but are less sensitive to angularity. The results indicate potential for using these parameters for quality control and quality assurance of asphalt mixture during production. [ABSTRACT FROM AUTHOR]

The fossil energy on the earth is limited, and with the energy shortage and the environment deterioration, there is an urgent need to develop and use renewable energy. Therefore, solar roads came into being. The current research on the structural performance of solar pavement is relatively lacking, especially the joint design between photovoltaic (PV) pavement unit structures. In order to fill this research gap, in this study, two different PIPVT unit joint designs for photovoltaic/thermal integrated pavement (PIPVT) are proposed, namely, dowel bar joint design and tongue-and-groove joint design. The load transfer capacity of the two joint designs is compared and analysed by ABAQUS simulation. By the result of simulation, the most unfavourable load position was determined, and the load transfer coefficients of the two joint designs were calculated to verify the reasonability of the two joint designs, and to compare and select the scheme. The results showed that the load transfer coefficient of the dowel bar is 75.7%, and its load transfer grade is medium; the load transfer coefficient of the tongue-and-groove joint is 88.9%, and its load transfer grade is excellent. It is recommended to use the tongue-and-groove joint design. [Display omitted] • Two joint designs were proposed and their load transfer capacity were compared. • The most unfavourable load position of the two joint designs was determined. • Load transfer coefficient of the dowel bar and tongue-and-groove are 83.8%, 91.5%. • It is recommended to use the tongue-and-groove joint design for PIPVT unit. [ABSTRACT FROM AUTHOR]

To investigate the effect of activated crumb rubber content on the molecular interactions and the properties of crumb rubber-modified asphalt (CRMA) with waste oil, six models of asphalt with various rubber dosages were developed using Materials Studio software, and the molecular dynamics performance of the system was further examined. Then, the fatigue and high- and low-temperature performances of the CRMA binders were characterized by dynamic mechanical experiments in the laboratory. The mean square displacement and diffusion coefficient were used to quantify the migration of molecules. The aggregation state of the components was evaluated using a radial distribution function. The bulk modulus of the CRMA models was calculated to study the mechanical properties. Dynamic shear and bending beam rheometer tests were implemented to evaluate the road performances of the CRMA binders. The results show that increasing the amount of powder could improve the mechanical properties of the asphalt, that is, the modulus of 70% of the asphalt was improved by 57.5%. The rubber and waste oil were evenly dispersed in the system, and the distribution of asphalt components was in accordance with the colloid theory. The temperature-sensitive properties of the rubber led to the improvement of road properties of the CRMA binders with the increase of the admixture. Combined with the distribution of molecules in the asphalt model, the results of rheological indexes show that the waste oil could improve the rheology and stability of binders. This will provide theoretical support for upgrading the content of crumb rubber in CRMA binders. [ABSTRACT FROM AUTHOR]