•Skeleton structure is the main body to transfer external loading in asphalt mixtures.•External loading was transferred effectively via main force chains for asphalt mixture skeleton.•Under external ...loading, AC type asphalt mixtures are easier to form III type force chains compared with others.
To overcome the deficiency of existing force chains identification criteria for evaluating asphalt mixture skeleton structure, a new force chains identification criteria and skeleton main force chains (MFC) are proposed and investigated in this study. Firstly, discrete element method (DEM) models of different asphalt mixtures were established to conduct virtual bearing plate tests. And then, asphalt mixture MFC morphological characteristics were analyzed. Relevant results indicate that although dense-graded asphalt concrete (AC) has more number force chains, stone mastic asphalt (SMA) and open-graded asphalt friction course (OGFC) have higher MFC number proportions. Under external loading, AC is easier to form III type force chains. SMA and OGFC have longer length MFC in terms of a single MFC. MFC of SMA is closer to linear compared with AC. This is beneficial to hold stability and transfer external loading for MFC. OGFC has the relatively worst quasi-linearity. Under thinner pavement structural thickness, SMA has a small external loading extension area compared with AC type asphalt mixture which is beneficial to improve external loading transferring efficiency.
Segregation of asphalt mixture is one of the main concerns causing early-stage failure of asphalt pavement. However, currently, the generation and degree of segregation are mostly judged according to ...the visual observation which is highly subjective and only applicable to large particle size and coarse asphalt mixture. Otherwise, facing to tedious and huge detection results, inefficient traditional recording and Excel presentation methods reveals a poor productivity. Therefore, this study proposes a new framework for quantitative analysis and visual presentation of segregation in asphalt mixture by integrating both digital image processing (DIP) and Building Information Modeling (BIM) technologies. In this method, a new algorithmic language is established for DIP approach, which could extract more image information, such as segmentation number and edge length in each area. Furthermore, a quantitative index is proposed to evaluate extent of segregation in asphalt mixture, which classifies segregation of asphalt mixture into mild, moderate and severe segregation. Besides, the framework incorporates BIM as a supporting technology to visualize the detection results of pavement segregation on 3D images. Meanwhile, warning points are generated for future maintenance. Finally, a case study demonstrates the feasibility of the proposed framework. This paper contributes by offering a new approach for the detection of the segregation in asphalt mixture by an easy operation and low cost way. Additionally, this approach also represents the DIP result by an intuitive review based on BIM, which improve the efficiency and decrease time-consuming during the construction phase.
•Quantitative analysis and visual presentation of segregation realized by DIP and BIM.•Image identification for the segregation is developed by image edge detection.•BIM is used for information storage and visual representation of detection result.•The framework is applied and validated by an expressway project in Cambodia.
Excessive and unregulated stacking of iron ore tailing (IOT) has created numerous environmental issues, which has drawn considerable attention to focus on the resource utilization of IOT. The present ...study attempts to investigate the feasibility of IOT as a filler alternative compared to limestone filler, from the perspective of asphalt mastic. To achieve that, the physical and chemical properties for two types of fillers (IOT and limestone) were tested by the laser particle size analyzer, X-ray fluorescence as well as scanning electron microscopy. Four filler/asphalt weight ratios (0.6, 0.8, 1.0, 1.2) were then selected to prepare asphalt mastics. The rotational viscosity test, temperature sweep test as well as multiple stress creep recovery test were conducted to assess the high-temperature performance for asphalt mastics. Furthermore, environmental and economical aspects were evaluated by the leaching toxicity and cost-benefit analysis. Results show that the IOT possesses a smaller particle size and larger specific surface area than the limestone, which contributes to the adsorption of asphalt on the particle surface. As for asphalt mastics, the replacement of filler by IOT can greatly enhance the viscosity, rutting factor as well as percentage of elastic recovery, and significantly reduce the non-recoverable creep compliance. Further, IOT has no risk of large-scale use as building material based on the leaching results, and considerable economic benefits (benefit-cost ratio >1) can be obtained from the utilization process. Consequently, IOT has a promising potential as an environment-friendly filler to replace the mineral filler in asphalt mixture in view of the pavement performance and environmental aspects.
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•The aging effects can enhance the cohesion of asphalt binders and mastics.•The indices K-B-G∗ and K-B-δ have the consistency to evaluate asphalt-filler interaction ability.•The deeper aging degree ...of asphalt binders is, the worse asphalt-filler interaction ability is.
The rheological properties of asphalt mastics and asphalt-filler interaction play key roles on the performances of asphalt mixtures. However, the rheological properties of asphalt mastics and asphalt-filler interaction are significantly influenced by aging which exists in the compaction stage of asphalt mixtures. In order to analyze the effects of aging on rheological properties of asphalt binders, asphalt mastics and asphalt-filler interaction, the Dynamic Shear Rheometer (DSR) tests and Bending Beam Rheometer (BBR) tests were conducted for unaged and aged specimens. Results indicate that the aging can enhance the cohesion properties of asphalt binders and mastics, and so the rutting resistance of asphalt binders and mastics is better with an increase in aging degree. However, the low temperature properties of asphalt binders and mastics are worse with an increase in aging degree. The two indices K-B-G∗ and K-B-δ were selected to evaluate asphalt-filler interaction ability. Results show that these two indices have the consistency to evaluate asphalt-filler interaction ability. And also the two indices can reflect the difference of interaction ability of different aged asphalt binders and fillers. The deeper aging degree of asphalt binders is, the worse asphalt-filler interaction ability is. Within the same aging degree, the interaction ability of asphalt 70# with higher asphaltene and resins contents is stronger than asphalt 90#. Therefore, the aging affects the asphalt-filler interaction ability via changes of asphalt active components.
•Limestone filler (LF) was substituted by iron tailing filler (ITF) in mastics under different f/b ratios.•The interaction between ITF and asphalt matrix was primarily physical.•ITF possessed a ...superior stiffening effect on mastics than LF.•A new index ΔTd was proposed to quantify the low-temperature performance of ITF mastics.•The substitution of ITF should be controlled within 1.0 f/b ratio.
Iron tailings, one kind of widespread solid waste, were preliminarily regarded as a potential substitute for mineral filler in asphalt mixtures. However, the overall rheological properties of asphalt mastics incorporating iron tailing filler (ITF) and the effect mechanism of ITF remain unclear, which is detrimental to the generalized utilization of ITF in asphalt pavement. To fill this gap, the present study selected ITF and limestone filler (LF) to fabricate mastics with four filler/asphalt weight (f/b) ratios (0.6, 0.8, 1.0, 1.2). The blending mechanism and surface morphology of mastics were revealed by Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. The rotational viscosity test, dynamic shear rheometer test as well as bending beam rheometer test, were conducted to comprehensively study the rheological behavior of mastics. A new index ΔTd was proposed to quantify the influence of ITF on low-temperature cracking performance. Results show that the interaction between ITF and asphalt matrix is predominantly physical, and ITF possesses a smaller particle size which is beneficial to stiffening the mastics. However, the worse infiltration and distribution uniformity of ITF in mastics than that of LF may result in poorer adhesion. Regarding the rheological behavior, the substitution of ITF can highly improve the viscosity, complex modulus, and creep stiffness while slightly decrease the phase angle, viscosity-temperature susceptibility, and m-value of mastics, indicating a higher stiffness and elasticity of ITF mastics. Notably, the plateau region of phase angle may appear in ITF mastics with high filler concentration at low frequencies, representing a more significant elastic response. Besides that, ΔTd remains between −3.5 and −1.1 ℃. These results prove that the substitution of ITF is advantageous for the anti-rutting performance of asphalt pavement but may jeopardize its workability and low-temperature cracking resistance in particular with the excessive incorporation (f/b ratio > 1.0) of ITF.
•A novel methodological framework analyzing degradation reliability was developed.•A novel method for the calculation of degradation reliability was established.•Flexural fatigue of asphalt mixture ...was statistically analyzed.•Distribution parameters were determined and compared using five numerical methods.•Reliability of asphalt mixture under fatigue loading was assessed.
This study aims to evaluate the evolution of reliability with number of cycles for asphalt mixture under repeated fatigue loading, i.e. degradation reliability. A novel methodological framework was developed to analyze the reliability, which integrates four theories (reliability theory, probability distribution function transformation, fatigue damage and Weibull distribution). Based on the developed framework, a novel and simple method was established to calculate the degradation reliability through a probabilistic simulation technique. Flexural fatigue performance of asphalt mixture was then analyzed statistically by Weibull distribution function. The five numerical methods were adopted and compared to estimate Weibull parameters. Kolmogorov-Smirnov test was conducted for further confirming the validity of this distribution. The reliability of asphalt mixture under fatigue loading was assessed using the established method. Results show that the randomness evolution behaviors of asphalt mixture under fatigue loading can be described by the developed framework. The degradation reliability under non-fatigue damage behaviors may be able to be calculated by the established method. The two-parameters Weibull distribution allows to describe fatigue life data of asphalt mixture. The evolutions of reliability with number of cycles show a decrease trend with three-stage. The degradation reliability of asphalt mixture in practical project should be larger than the value corresponding to mean fatigue life as far as possible. Method of moments should be adopted to estimate distribution parameters for the evaluation of degradation reliability of asphalt mixture, the health state of asphalt mixture is thus early warned timely.
To address the challenge of sealant debonding due to cyclic temperature variations, a new pavement crack repair sealant which can achieve two-way shape memory deformation is developed. The developed ...crack sealant is a shape memory liquid crystal elastomer (SMLCE), designed to exhibit the deformation characteristics of heat contraction and cold expansion. First, the material composition and preparation process of the developed SMLCE are given. Thermodynamic properties, phase transition temperatures and molecular structures are analyzed based on DSC and FITR. The effects of the crosslinker and chain extender ratios and the key preparation processes on the two-way shape memory deformation and mechanical performance of SMLCE are systematically analyzed. Based on the analysis, the optimum ratio of SMLCE is determined to be 1:15 and the optimum secondary crosslinking preparation process is 150% orientation stretching. Under the optimal solution, the developed SMLCE can achieve the multiple two-way shape memory reversible deformation with a maximum 46% deformation in the temperature range of -20°C∼120°C. At the same time, the developed SMLCE has excellent mechanical properties, with a tensile strength of 20.7Mpa and an elongation at break of 322%. It also exhibits good low-temperature deformation capabilities at -10°C and above. Finally, the suitability and application potential of the developed two-way SMLCE as a pavement crack sealant are assessed. The developed SMLCE has good adaptability in most climate zones, which indicates its great potential as a pavement crack sealant. This research provides a new way for the pavement crack repair.
•The developed SMLCE sealant with a two-way shape memory deformation effect.•Multiple two-way shape memory reversible deformation ability in the range of -20°C∼120°C.•Under the optimal solution, the maximum shape memory shrinkage rate reaches 47%, the tensile strength reaches 20.7 MPa, and the elongation at break reaches 322%.
Crack is a typical distress on bridge deck asphalt pavement (BDAP), which destroys the integrity and continuity of the pavement structure. However, the research on the crack propagation mechanism of ...BDAP is still limited. In this study, the three-point bending test was performed to investigate the propagation process of cracks in BDAP. Pre-cracks were set in the specimens with different depths (8 mm, 12 mm, 15 mm) and 4 mm widths, and two asphalt rubber hot-mix (ARHM) mixtures (ARHM-13 and ARHM-20) were selected. The critical fracture load, fracture energy, and fracture toughness were compared to investigate the crack resistance of ARHM-13 and ARHM-20 mixtures. In addition, the upper and lower layers of double-layer composite pavement specimens were fabricated with ARHM-13 and ARHM-20 mixture, respectively. The propagation process of the top-down crack (TDC) and reflection crack (RC) were investigated at different locations on the specimens. The test results show that the crack resistance of ARHM-20 mixtures is greater than that of ARHM-13 mixtures, and ARHM-20 mixtures should be used in the lower layer of BDAP to limit the propagation process of the reflection crack to the upper layer. The cracks propagated firstly from the RC and formed a through crack at the TDC in the specimens under the three-point bending loading action. The presence of TDC was found to accelerate the crack propagation of RC and exacerbate the failure of the BDAP. The crack length and deflection angle were determined by the pre-crack location. Furthermore, the decrease in temperature led to an increase in crack propagation velocity. The average propagation velocity increased from 0.03 mm/s to 0.55 mm/s as the temperature decreased from 20 ℃ to −20 ℃.
•The crack resistance of the asphalt rubber hot-mix (ARHM) mixture was studied at different pre-crack depths and temperatures.•Study the crack propagation when top-down cracks and reflection cracks coexist on double-layer composite pavement specimens.•The effect of initial pre-crack location and temperature on crack path, deflection angle, and propagation velocity.
•The long-term effectiveness of preventive maintenance treatments (PMTs) on pavement performance was evaluated.•A new framework was established to evaluated pre-treatment pavement condition.•A new ...indicator was proposed to characterize average long-term effectiveness increment.•The proposed indicator is capable of evaluating the long-term effectiveness of PMTs.•A critical pavement condition exists in the long-term effectiveness of PMTs on each performance respectively.
The present study evaluated the long-term effectiveness of preventive maintenance treatments (PMTs) on pavement performance using the data collected in the Specific Pavement Studies-3 (SPS-3) of the Long-Term Pavement Performance (LTPP) program. The PMTs included thin overlay, slurry seal, crack seal and chip seal. Pavement performances included roughness, rutting, transverse cracking, longitudinal cracking and alligator cracking. A new framework was established in this study to evaluate pre-treatment pavement condition. Weighted distress was adopted to describe average long-term performance and a new indicator was proposed to characterize average long-term effectiveness increment. Scatterplot analysis, cumulative frequency distribution, average long-term effectiveness increment and pair-samples t-test were conducted to investigate the long-term effectiveness. Results indicate that the results from the four analysis methods are similar, so the proposed new indicator is capable of evaluating the long-term effectiveness of PMTs. Meanwhile, thin overlay and crack seal are the best and worst PMTs on each performance, respectively. In addition, there may be a critical original pavement condition in terms of the long-term effectiveness of PMTs on each performance respectively. The findings in this study may supply guidelines for the implementation of preventive maintenance decision-making.
•The long-term effectiveness of PMTs was compared under various environmental conditions.•The proposed average increment indicator allows to assess the long-term effectiveness of PMTs.•The ...effectiveness of treatments is different under various environmental conditions.
As an essential part of the pavement maintenance management system, preventive maintenance plays an important role in the asphalt pavement maintenance decision-making. In order to compare long-term effectiveness of preventive maintenance treatments (PMTs) under various environmental conditions, Specific Pavement Studies-3 (SPS-3) data were extracted from Long-Term Pavement Performance (LTPP) program in this study. Environmental conditions include climate, traffic level and pre-treatment pavement condition. Weighted distress was used to characterize an average long-term performance. An average increment indicator was proposed to qualitatively analyze the effects of these conditions on the effectiveness of treatments. Logistic regression was adopted to quantity these effects. Implementation proposals were recommended in terms of PMTs. Results show that thin overlay is the most effective in comprehensive treatment of all performances, followed by chip seal, slurry seal and crack seal. Freeze condition has a significant influence on the effectiveness of treatments. Moisture level significantly influenced rutting and transverse cracking. Traffic level is a main factor for the effectiveness of treatments on roughness, longitudinal cracking and alligator cracking. The effects of pre-treatment pavement condition on only roughness and rutting are significant. The proposed average increment indicator allows to assess the long-term effectiveness of PMTs and the influence of different factors.
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