Abstract ：

This paper investigated the damage healing, local life compensation and intrinsic healing characteristics of asphalt binder. The damage healing (Delta S) is independent of damage level and the percent local life compensation (%Delta N) increases with a higher strain amplitude in TSH test. The integrated Delta S-Delta N analysis is recommended for the healing compensation characterization. The totally stored pseudo strain energy (PSE) to counteract healing recovery is linearly linked to the Delta S regardless of the loading modes, strain amplitudes and rest periods. A new parameter of average stored PSE (QH) is proposed to reveal the intrinsic healing potential and characteristics.

Keyword ：

Healing compensation Healing compensation Asphalt binder Asphalt binder Fatigue damage Fatigue damage Rest period Rest period

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Abstract ：

With the social economy gradual transforming to green and sustainable, the odor pollution in the process of road asphalt paving has become an environmental problem that cannot be ignored. In this study, GC-MS and gas detector are used for qualitative and quantitative analysis of volatile compounds produced by five asphalt materials. On this basis, combined with the odor threshold, the odor activity value (OAV) of each compound is calculated, and the odor of asphalt is analyzed by the method of the sum of odor activity value (SOAV), and the odor contribution of each compounds is classified according to the chemical properties to find the rule of odor contribution between each group. The results show that the main contribution groups of odor activity value of asphalt volatiles are alkanes, aldehydes, benzene series, and hydrogen sulfide. The evaluation process can be simplified on the basis of the existing odor evaluation: the concentration of each group is measured, and the sum value of the odor activity values of various asphaltenes is calculated by combining the odor threshold of each compound. Among them, the odor threshold of hydrogen sulfide does not need to be analyzed and can be obtained. Therefore, the odor threshold of alkanes, aldehydes, and benzene series in volatile compounds of different kinds of asphalt materials is further calculated, and the group odor threshold of three kinds of groups is finally determined. After determining the group odor threshold of the three types of groups, combining the concentration of alkanes, aldehydes, benzene series, and hydrogen sulfide, the sum value of the activity value of various asphalt odor is calculated and the error analysis is conducted with the measured value. It is verified that the odor characteristics of different kinds of asphalt can be analyzed by the simplified evaluation method of asphalt odor characteristics.

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Abstract ：

Traditional evaluation parameters for multiple stress creep recovery (MSCR) test and linear amplitude sweep (LAS) test are difficult to deeply and theoretically characterize the high-and intermediate-temperature rheo-logical behaviors of polymer modified asphalt (PMA) binders and mastics. In this paper, one neat asphalt and four types of PMA binders and mastics are selected (i.e., the rubber modified ones, SBS modified ones, ther-moplastic elastomer modified ones and SBS/Rubber modified ones). Two new analysis methods, i.e. Burgers model and damage mechanics-based crack growth model, are applied in analyzing the high-and intermediate -temperature rheological behaviors of PMA materials respectively. The Burgers model results indicate adding filler decreases the viscous deformation, and leads to lower non-recoverable compliance in the MSCR test. The polymer modification transfers the delayed elastic deformation to elastic deformation, thus causing more excellent rutting resistance. The damage mechanics-based crack growth model analysis reveals that adding filler enhances the crack growth rate and crack length, thus sacrificing the fatigue resistance. By contrast, the polymer modification enhances the fatigue resistance regardless of polymer types. Notably, a two-stage pattern based on crack growth rate and energy release rate was further proposed to identify the crack initiation and propagation of PMA materials. Specifically, 30% rubber modified asphalt binders and mastics perform best in both rutting and fatigue resistance. Moreover, PMA binders and mastics have strong correlation based on the recovery percentage and delayed elastic deformation. The correlation of fatigue life between PMA binders and mastics is very sig-nificant, however there was no obvious correlation in terms of crack length.

Keyword ：

Intermediate-temperature behavior Intermediate-temperature behavior Correlation analysis Correlation analysis Crack growth model Crack growth model High-temperature behavior High-temperature behavior PMA binders and mastics PMA binders and mastics Burgers model Burgers model

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Abstract ：

The crack initiation behavior of asphalt binders plays a significant role in the evolution of fatigue damage. In this study, the crack initiation process of asphalt binders is characterized by employing Griffith's energy balance principles and the surface energy theory. The localized energy redistribution caused by crack initiation is quantified. A prediction model of crack initiation length is developed based on the asphalt crack initiation criterion. The effect of fatigue loading amplitude and the testing temperature in the progression of crack initiation are further investigated. The results show that the fatigue damage process of asphalt in the time sweep test consists of two stages: crack initiation and "factory-roof" cracking. The material-dependent parameters can be utilized to predict the crack initiation length at different strain levels. The fatigue crack initiation life of asphalt binders is decreased with a greater strain level. However, the crack initiation resistance of the asphalt is enhanced by the decrease of testing temperature.

Keyword ：

road engineering road engineering asphalt binder asphalt binder surface energy surface energy time sweep time sweep crack initiation criterion crack initiation criterion

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Abstract ：

The objective of this work is to explore the damage healing characteristics between asphalt binder and mastic using newly developed testing procedures under different loading modes. Both the TS and LAS based-healing procedures are conducted on binder and mastic scales. Experimental and analytical results indicate that the addition of mineral powder into binder does not change the fatigue damage evolution trend in the LAS test; however, the effect of mineral powder addition on the HMC shows obvious asphalt-type dependence. Based on the newly proposed QH index and the QHR- based healing criterion, the healing performance correlation between asphalt binder and mastic are interactively explored. The binder and mastic QH indices display a good linear relationship, regardless of loading modes and binder type. Meanwhile, a certain correlation is also found for the damage healing criteria among these two material scales.

Keyword ：

damage healing characteristics damage healing characteristics asphalt binder and mastic asphalt binder and mastic road engineering road engineering loading modes loading modes

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Abstract ：

Volatile organic compounds (VOCs) have adverse effects on the environment and human health. SBS modified asphalt mixture releases a large amount of VOCs during construction under high-temperature conditions. In this study, the effect of activated carbon on the road performance and VOCs emissions behavior of SBS modified asphalt mixture was comprehensively investigated. The inhibition of VOCs in asphalt mixture was analyzed in three levels of total concentration-group concentration-component concentration by GC-MS. The results indicate that activated carbon can improve the water stability of asphalt mixtures, while it has adverse effects on high-temperature stability and low-temperature crack resistance. Activated carbon can effectively inhibit VOCs emissions from asphalt mixtures. The inhibition rate of VOCs increases with the rising content of activated carbon. The total VOCs concentration of SBS modified asphalt mixture is reduced by 46.4% with the addition of 5% activated carbon. Activated carbon can effectively suppress most of the groups and components in VOCs, but it also shows a certain degree of selectivity. Aldehydes and formaldehyde are the group and component with the highest content in VOCs that can be effectively controlled, their concentration is decreased by 51% and 62% with the addition of activated carbon. However, the concentration of some groups and components increases with the addition of 3% activated carbon, such as olefins and cyclopentane, while the emissions of these groups and components can be inhibited with the addition of 5% activated carbon. Activated carbon has a certain negative effect on the inhibition of some groups and components, such as aromatic hydrocarbons and benzene. On the whole, SBS modified asphalt mixture containing 5% activated carbon has better comprehensive performance through multi-objective optimization evaluation of environmental and technical performance, which can meet the road performance requirements and show the best VOCs suppression effect.

Keyword ：

Volatile organic compounds Volatile organic compounds Activated carbon Activated carbon SBS modified asphalt mixture SBS modified asphalt mixture Road performance Road performance Emissions reduction characteristics Emissions reduction characteristics

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Abstract ：

Understanding of the healing behavior of asphalt binder is critical for fatigue modeling of asphalt paving materials. Binder-healing characterization based on the traditional time sweep test is time-consuming. The purpose of this study was to compare the damage-healing behavior of various neat and modified asphalt binders with the newly developed linear amplitude sweep healing (LASH) procedure, followed by verification on a simplified LASH (S-LASH) procedure to alternatively estimate binder-healing characteristics with reasonable testing efficiency. Thirteen neat and modified asphalt binders (17 sample conditions) were selected and respectively analyzed with standard LASH and S-LASH. Standard LASH showed that the healing performance of neat binders with the same penetration grade generally aligns with increasing damage. For the neat binders with different penetration grades, softer binders have better healing capacity. The negative aging effect on binder healing was demonstrated. Meanwhile, the healing master curve (HMC) was effective in comparing binder-healing characteristics under prefailure conditions. The healing rate (H-R) for the tested binders basically varied from 0.1 to 0.2. Finally, mean absolute error (MAE) analysis of HMC and H-R between standard LASH and S-LASH indicated 50% S-f (damage intensity at failure) with a 900-s rest period to be a critical LASH testing condition to derive reliable healing HMC and H-R values. S-LASH is also recommended to estimate binder healing characteristic with significantly reduced testing time. (C) 2021 American Society of Civil Engineers.

Keyword ：

Asphalt binder Asphalt binder Rest period Rest period Percent healing Percent healing Healing master curve Healing master curve Fatigue damage Fatigue damage

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Abstract ：

This paper presents a viscoelastic fatigue and fracture (VEFF) modeling and its preliminary application to asphalt binder under cyclic loading. Both traditional time sweep (TS) fatigue test and linear amplitude sweep (LAS) test are performed. The failure definition is unified from the peak of fracture energy. The binder fatigue performance is dominated by its resistance to crack propagation. A mechanistic criterion paradigm is established to be independent of the strain ramping rate in LAS and strain amplitude in TS tests. The proposed model is verified by various binders, demonstrating the reasonable use of the LAS as an accelerated fatigue protocol.

Keyword ：

Asphalt Asphalt Fracture Fracture Crack propagation Crack propagation Crack initiation Crack initiation Fatigue life Fatigue life Fatigue Fatigue

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Abstract ：

Several previous studies have demonstrated that bio-asphalt derived from Waste Cooking Oil (WCO) displays superior performance in cracking resistance at low and medium temperature, but inferior in high temperature rutting resistance. This study aims to further improve the rutting resistance of WCO based bio-asphalt by a compound modification with Organized Montmorillonite (OMMT). One neat asphalt binder with penetration grade of 90 is selected in this study. The WCO based bio-oils are firstly mixed with neat binders followed by further modified with the OMMT additives. The frequency sweep, linear amplitude sweep (LAS) and multiple stress creep recovery (MSCR) tests are respectively conducted for evaluation of the linear viscoelastic properties, fatigue and rutting resistance. Experimental results demonstrate again that the fatigue resistances of bio-binders are improved compared to the base asphalt whereas the addition of bio-oil obviously reduces the binder rutting resistance at high temperature. However, the OMMT addition into the bio-asphalt is found to effectively enhance the rutting resistance when increasing the OMMT content without compromising the fatigue performance. Therefore, it can be preliminary concluded that the Bio/OMMT compound modification approach can be utilized to address the rutting potential concern of WCO based bio-binders at high temperature. Furthermore, the Response Surface Methodology (RSM) is employed to model the rheological properties of Bio/OMMT compound modified binder under various modifier weights, in which the damage characteristic and performance index can be effectively estimated.

Keyword ：

Bio-Asphalt Bio-Asphalt Rheology Rheology Aging Aging Rutting Rutting Fatigue Fatigue Performance Prediction Performance Prediction

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Abstract ：

Generally, the cohesive healing within the asphalt composites and the adhesive healing from the asphalt-aggregate interface always occur simultaneously in the asphalt concrete with growing damage. This study aims to investigate the cohesive and adhesive healing behaviors of asphalt binder respectively by utilizing the newly developed linear amplitude sweep based healing (LASH) and binder bond strength based healing (BBSH) tests. Seven unmodified asphalt binders and one styrene–butadienestyrene (SBS) polymer modified binder are selected in this study. A fracture mechanics based crack growth approach is proposed to define the cohesive healing recovery in the LASH test with two percent healing parameters, in terms of the %Ha of the crack length recovery and the %HA of the sample intact area recovery. In pre-failure conditions, the measured %Ha can at least reach beyond 30% while the %HA is normally within 30% for tested binders. Meanwhile, the %Ha results show more consistent trends to the traditional simplified-viscoelastic continuum damage (S-VECD) based LASH data interpretation. Furthermore, the cohesive failure occurrence is verified to significantly impact the healing performance comparison. The cohesive healing behaviors of neat and SBS binders respectively in pre-failure and post-failure conditions are distinguished to each other, which are validated either from S-VECD or crack growth approaches. Regarding to the binder adhesive healing behavior, it is observed that the presence of water and the using of granite substrate generally have positive effects on adhesive healing recovery in the BBSH tests. The SBS modification generally displays lower adhesive healing percentages than the neat binders especially in the wet conditions. Though no clear relationships can be found between the cohesive and adhesive healing behaviors in this study, it is recommended to quantify the binder contribution to the adhesive healing process in the future work. © 2021 Elsevier Ltd

Keyword ：

Concrete aggregates Concrete aggregates Styrene Styrene Binders Binders Recovery Recovery Fracture mechanics Fracture mechanics Adhesives Adhesives Cracks Cracks Asphalt Asphalt Self healing concrete Self healing concrete

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