| 1. |
|
|
| 2. |
|
|
| 3. |
|
|
| 4. |
|
|
| 5. |
- Ding, Heyang, et al.
(författare)
-
Virtual strain loading method for low temperature cohesive failure of asphalt binder
- 2023
-
Ingår i: Journal of Road Engineering. - : Elsevier BV. - 2097-0498 .- 2773-0077. ; 3:3, s. 300-314
-
Tidskriftsartikel (refereegranskat)abstract
- Cohesive failure is one of the primary reasons for low-temperature cracking in asphalt pavements. Understanding the micro-level mechanism is crucial for comprehending cohesive failure behavior. However, previous literature has not fully reported on this aspect. Moreover, there has been insufficient attention given to the correlation between macroscopic and microscopic failures. To address these issues, this study employed molecular dynamics simulation to investigate the low-temperature tensile behavior of asphalt binder. By applying virtual strain, the separation work during asphalt binder tensile failure was calculated. Additionally, a correlation between macroscopic and microscopic tensile behaviors was established. Specifically, a quadrilateral asphalt binder model was generated based on SARA fractions. By applying various combinations of virtual strain loading, the separation work at tensile failure was determined. Furthermore, the impact of strain loading combinations on separation work was analyzed. Normalization was employed to establish the correlation between macroscopic and microscopic tensile behaviors. The results indicated that thermodynamic and classical mechanical indicators validated the reliability of the tetragonal asphalt binder model. The strain loading combination consists of strain rate and loading number. All strain loading combinations exhibited the similar tensile failure characteristic. The critical separation strain was hardly influenced by strain loading combination. However, increasing strain rate significantly enhanced both the maximum traction stress and separation work of the asphalt binder. An increment in the loading number led to a decrease in separation work. The virtual strain combination of 0.5%-80 provided a more accurate representation of the actual asphalt's tensile behavior trend.
|
|
| 6. |
- Hu, Chichun, et al.
(författare)
-
Experimental Study of Dowel Bar Alternatives Based on Similarity Model Test
- 2017
-
Ingår i: Advances in Materials Science and Engineering. - : Hindawi Limited. - 1687-8434 .- 1687-8442.
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, a small-scaled accelerated loading test based on similarity theory and Accelerated Pavement Analyzer was developed to evaluate dowel bars with different materials and cross-sections. Jointed concrete specimen consisting of one dowel was designed as scaled model for the test, and each specimen was subjected to 864 thousand loading cycles. Deflections between jointed slabs were measured with dial indicators, and strains of the dowel bars were monitored with strain gauges. The load transfer efficiency, differential deflection, and dowel-concrete bearing stress for each case were calculated from these measurements. The test results indicated that the effect of the dowel modulus on load transfer efficiency can be characterized based on the similarity model test developed in the study. Moreover, round steel dowel was found to have similar performance to larger FRP dowel, and elliptical dowel can be preferentially considered in practice.
|
|
| 7. |
- Ma, Ziye, et al.
(författare)
-
Optimized bio-oil emulsification for sustainable asphalt production: A step towards a low-carbon pavement
- 2024
-
Ingår i: Construction and Building Materials. - : Elsevier BV. - 0950-0618 .- 1879-0526. ; 419
-
Tidskriftsartikel (refereegranskat)abstract
- Bio-oil, derived from biomass, offers a sustainable alternative to petroleum-based asphalt binders in construction. However, its high oxygen content and temperature sensitivity pose challenges. This study explored the possibility of using emulsification technology to produce and apply emulsified bio-asphalt at a relatively low-temperature, aiming for sustainable high-value utilization. Three preparation processes were proposed in this study, including modification followed by emulsification (Process A), emulsification followed by modification (Process B), and separate emulsification followed by mixing (Process C). Based on the thermal characteristics of bio-oil, the optimal emulsification temperature was determined to be 80 ± 1 ℃. Through an I-optimal experimental design combined with response surface methodology (RSM), the influence of bio-oil and emulsifier on the performance of emulsified bio-asphalt was investigated for each process. It was found that Process C can leverage the low-temperature extensibility and interfacial adhesion benefits of bio-oil to prepare stable emulsified bio-asphalt with superior comprehensive performance. Based on desirability optimization methodology, the study optimized bio-oil and emulsifier content. The recommended composition is 10.37% bio-oil and 3.53% emulsifier for Process C. Through practical observation, emulsified bio-asphalt production offered environmental benefits, reducing emissions of CO2 and harmful gases, particularly VOCs and NOx. Additionally, adopting bio-oil aligned with carbon neutrality goals, potentially sequestering 880,000 tons of carbon annually in China's road construction and maintenance activities.
|
|
| 8. |
- Tan, Zhifei, et al.
(författare)
-
Constitutive modelling and systematic evaluation of asphalt concrete’s viscoelastic tension-compression asymmetry effect on pavement performance
- 2024
-
Ingår i: The international journal of pavement engineering. - : Informa UK Limited. - 1029-8436 .- 1477-268X. ; 25:1
-
Tidskriftsartikel (refereegranskat)abstract
- Asphalt concrete (AC) exhibits significant tension-compression (TC) asymmetry, which is currently not considered in pavement design. This study develops a novel temperature-dependent dual viscoelastic model to quantitatively capture the viscoelastic behaviour of AC. Unlike the conventional viscoelastic constitutive model, the proposed model decomposes strain into tensile and compressive components to characterise AC’s TC asymmetry. Additionally, a systematic modelling framework with intrinsic TC asymmetry is developed for the first time to predict the response of pavement under moving tire load. The results illustrate that implementing the proposed dual viscoelastic model enlarges both the vertical deformation of pavements and the tensile and shear strains in the AC layers, bringing it closer to the realistic scenario compared to the conventional model that only considers compression properties. Furthermore, high temperatures and low vehicular speeds exacerbate the substantial effects of AC’s TC asymmetry on asphalt pavement. This study provides a valuable method to capture AC’s TC asymmetry and predict pavement response more accurately, giving better insight into pavement response and enhancing pavement design and maintenance.
|
|
| 9. |
- Tan, Zhifei, et al.
(författare)
-
Multiscale characterization and modeling of aggregate contact effects on asphalt concrete's tension–compression asymmetry
- 2023
-
Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 232
-
Tidskriftsartikel (refereegranskat)abstract
- Asphalt concrete (AC) exhibits significant tension–compression (TC) asymmetry and aggregate contacts can be one of the critical contributors to this behavior. Nevertheless, the underlying mechanisms are still unclear, and there has been no study to quantify this behavior. To fill the research gap, multiscale characterization and modeling on AC were performed in this study. At the microscale level, nanoindentation tests were conducted to characterize the aggregate contact characteristics in the contact region (CR). The CR was found to have a sandwich-like structure consisting of two interfacial layers, large filler particles, and asphalt mastic. Accordingly, micromechanical models of CR were developed to predict its mechanical behavior in tension and compresison (T&C). The modeling results showed that aggregate contacts significantly increase the compressive modulus, leading to the substantial TC asymmetry of CR. The predicted viscoelastic properties of CR were further applied to the developed mesostructural model of AC. The predicted master curves in T&C showed significant asymmetry and quantitatively agreed with the experimental ones, demonstrating the effectiveness of the adopted modeling approaches. This study is the first study to quantify the asymmetric performance of AC. The outcomes can be applied to evaluate AC's TC asymmetry effects on pavement performance.
|
|
| 10. |
- Tan, Zhifei, et al.
(författare)
-
Numerical modeling of the mechanical response of asphalt concrete in tension and compression
- 2023
-
Ingår i: Mechanics of materials. - : Elsevier BV. - 0167-6636 .- 1872-7743. ; 187
-
Tidskriftsartikel (refereegranskat)abstract
- Asphalt concrete (AC) shows significant tension-compression (TC) asymmetry, i.e., different properties in tension and compression (T&C). This asymmetry may profoundly affect AC's performance and deterioration in the field, but limited studies have been performed to quantify this behavior. This study aims to quantitively characterize the global and local mechanical responses of AC in T&C through numerical modeling. To this end, three AC mixtures: the gap-graded SMA10, dense-graded AC20, and open-graded mixtures PA13, were evaluated experimentally and numerically. Digital image processing was used to generate image-based AC models with contact regions (CR), and dynamic simulations were conducted using the steady-state dynamics (SSD) approach. The results indicated that the measured and predicted master curves for AC in T&C qualitatively agree and demonstrate significant asymmetry, with higher moduli but lower phase angles in compression compared to tension. Among the mixtures, PA13 exhibited the most pronounced asymmetry, followed by SMA10 and AC20. Statistical analyses of local stress and strain found that the stress and strain in different phases show significant variations, with more pronounced disparities observed at lower frequencies. Notably, at 10−6 Hz for PA13 in compression, the stress within the aggregate phase exceeded that of the matrix phase by over 250 times, while the strain within the matrix phase surpassed the aggregate phase by more than 600 times. To enhance pavement durability, it is recommended to consider AC's TC asymmetry in pavement design.
|
|
