Dowel bar misalignment causes stress concentration in jointed concrete pavements, and misaligned dowel bars may lose their ability to transfer loads. To examine this problem, a concrete damage ...plasticity (CDP) model and a method were implemented using ABAQUS to evaluate its parameters. The CDP model simulated the stress-strain relationship for tension and compression in concrete specimens, and was validated through experimental testing. A three-dimensional finite element model of a misaligned dowel in a jointed concrete pavement was developed, and the equivalent stress, plastic strain, and plastic damage under loads for various misalignment conditions were determined. The simulation results of uniaxial tension and compression in a concrete sample were compatible with the experimental results, demonstrating the high accuracy of the CDP model. Under the action of a wheel load, the concrete below a misaligned dowel undergoes plastic damage. The damage extended from the bottom of the dowel to the sides as the misaligned dowel deviated vertically from the alignment with the pavement's longitudinal axis, especially in the case of twin bars misaligned in opposite directions. The plastic damage ratio is close to unity, which indicates complete failure of the concrete below the misaligned dowel. The equivalent stress below the dowel tends to be zero and shifts to the sides of the dowel. Consequently, the concrete below the misaligned dowel failed to support the load, reducing the load-carrying capacity of the dowel. When a fully elastic model was used, the stresses below the dowel exceeded the ultimate strength of the concrete, which contradicts the actual occurence. Therefore, the CDP model is recommended for analyzing the stress in the concrete around a misaligned dowel.
High-precision 3D point cloud data have various analyses and application use cases. This study aimed to achieve a more precise noise reduction of the raw 3D point cloud data of asphalt pavements ...obtained using 3D laser scanning. Hence, a noise-reduction algorithm integrating improved Gaussian filtering and coefficient of variation was developed. A portable laser scanner was used to collect raw, high-precision 3D point cloud data of surface textures from pavement slab samples prepared with three different types of asphalt mixtures: AC-13, SMA-13, and OGFC-13, as well as asphalt from the test sections of the Yakang Expressway. An improved Gaussian filtering and Gaussian filtering that extracts noise using the coefficient of variation were used to filter out the obvious outlier noise and small-scale burr noise, respectively. Finally, the filtering effect of the proposed algorithm, Gaussian filtering, median filtering, and mean filtering on raw 3D point cloud data of pavement textures was evaluated through subjective visual quality and objective index evaluations. The results showed that the proposed algorithm filters out noise while preserving the micro-texture structure information, outperforming Gaussian filtering, median filtering, and mean filtering.
Basalt fiber is prone to slip and fall off in asphalt system. To improve the interfacial adhesion strength between basalt fibers (BFs) and asphalt, titanate coupling agents (TCAs) were applied to ...BF-reinforced asphalt. The mechanical properties of fibers with TCA concentration (6%, 8%, 10%, 12%) and infiltration time (10 min, 30 min, 60 min, 90 min) were tested by monofilament tensile strength test to obtain the best treatment conditions. The crystal phase, functional group, microstructure, and elemental changes of the TCA-treated basalt fibers were characterized by X-ray diffractometer, Fourier infrared spectroscopy (FT-IR), and X-ray energy-dispersive spectroscopy. The controlled group (untreated basalt fibers) was also prepared for comparison. Meanwhile, the adhesion work and interfacial bonding strength between asphalt and basalt fibers were compared and quantitatively assessed through pull-out tests. Additionally, the thermal stability of asphalt was evaluated using the differential scanning calorimetry test, while the surface morphology of the fractured asphalt sections was observed through scanning electron microscopy. The results show that the surface of basalt fibers was chemically modified by TCA successfully, forming octopus-inspired micro-sucker coated. Through this process, the nascent Si–O–Ti bond acts as a tie connecting the basalt and asphalt surface, which promoted the adhesive properties of BF to asphalt. Compared with the control group, the adhesion work and adhesion energy of basalt fibers-asphalt increased by 20.05% and 26.82%, respectively, and the thermal stability was improved. The experimental results show that after the treatment of the fiber surface by TCA, the interaction between the fiber and the asphalt is strengthened, and the interfacial bonding morphology is improved.
Crafting Styrene-Butadiene-Styrene (SBS) polymer into the bitumen can notably improve the elastic response of the polymer modified bitumen (PMB), which will significantly enhance the overall ...performance of bituminous pavement. But the molecular mechanism of the PMB’s unique entropy elasticity has not been fully understood yet. The prominent entropy-elasticity of SBS polymer modified asphalt was investigated in this study. To do so, Fourier Transform Infrared (FTIR), Gel Permeation Chromatography (GPC) and Dynamic Mechanical Analysis (DMA) were conducted to investigate the molecular modification mechanism of PMB. Afterwards, polymer molecular model with a polymerization degree over 2000 is constructed and dynamic simulation is conducted to reveal the mesoscopic mechanism of SBS polymer’s entropy elasticity. As for macroscopic evaluation, a series of creep and recovery tests associated with different testing temperatures (10 °C to 100 °C with a 6 °C gap), recovery times (0.01 s, 0.1 s, 1 s, 4 s and 9 s) and SBS dosages (0 %, 2.5 %, 4.2 %, 7.5 %) were carried out to characterize the elasticity of various PMBs. The results show that plain bitumen mainly shows energy-elasticity, which is small, instantaneous and highly temperature-dependent, while PMB mainly shows entropy-elasticity, which is strong, delayed and less temperature-dependent. Under the condition of low temperature and short recovery time, the bitumen molecules freeze and prevent the SBS polymer to demonstrate its entropy-elasticity, hence the energy-elasticity dominates. Higher temperatures and long recovery time render the SBS molecule more time to relax and thus the entropy-elasticity dominates. The predominant influence of entropy-elasticity in PMA leads to a unique increasing recovery rate within a specific high-temperature range. This phenomenon can be utilized as a fingerprint approach for the identification of the entropy-elasticity and polymer modification.
Interface bonding between asphalt layers plays a vital role in ensuring the proper functionality of pavement structures. Interlayer Shear Strength (ISS) is recognized as an indicator quantifying the ...interface bonding quality. Consequently, accurate evaluation and prediction of the ISS is imperative in determining the performance of asphalt pavement structures. By conducting laboratory experiments and employing machine learning (ML) techniques, this research aims to predict and assess the ISS in asphalt pavement. In this regard, the classification and regression trees (CART) model was proposed based on measured data collected from laboratory experiments. Three experimental factors of curing temperature, normal stress, and tack coat application rate were selected as variables. The findings showed that the developed CART model explained over 98% of the experimental data in a relatively short period. The curing temperature was found to have the most significant influence on the ISS, followed by normal stress and tack coat dosage. Moreover, a parametric analysis of the interaction effects of input parameters on the ISS revealed that higher curing temperature and lower normal stress reduced the ISS. In contrast, a high tack coat application rate and low normal stress corresponded to a lower ISS of the asphalt pavement. The outcomes of this study could pave the way for the realization of a reliable and efficient design of interlayer bonding between asphalt pavement layers.
To examine the three-dimensional texture structure of SMA-13 asphalt pavement and assess its anti-skid performance, a light gradient-boosting machine evaluation model was developed using non-contact ...three-dimensional laser-scanning technology. The study focused on collecting three-dimensional texture data from newly laid SMA-13 asphalt pavement. Subsequently, wavelet transform was employed to reconstruct the pavement’s three-dimensional texture, and discrete Fourier transform was utilized to separate macro- and microtextures, enabling the calculation of their characteristics. The macro- and micro-characteristics of the three-dimensional texture and friction coefficient were input into the model. A comparative analysis with linear regression and a random forest model revealed superior accuracy and efficiency in the model. The training set R2 is 0.948, and the testing set R2 is 0.842, effectively enabling the evaluation of pavement anti-skid performance. An analysis of parameter importance indicated that Rku and MPD are still effective indicators for evaluating skid resistance. Furthermore, diverse texture indexes exhibited varying effects on the anti-skid performance. The established asphalt pavement anti-skid evaluation model serves as a theoretical foundation for understanding the actual influence on pavement anti-skid performance.
The grooved-filled asphalt pavement has certain advantages in terms of pavement ice-breaking and anti-skid. However, the performances of the filling material limit its development. In this study, a ...polyurethane urea (PUU) - waste rubber particles (WRP) composite filling material was prepared by using a polyurethane (PU) and adding polyurea (PUa) with a similar microstructure as the cementing material, and adding WRP as the elastic reinforcing phase. The proportions of nine PUU-WRP composite materials were designed by changing the particle size and content of WRP, and then the filled composite materials were evaluated in terms of physical and mechanical properties, ice adhesion properties, interface bonding properties and aging resistance. The test results showed that the shore hardness, tensile strength, compression permanent deformation, and contact angle of PUU-WRP composite decreased as content of the WRP increased. Except the ice adhesion force results were the opposite. On the other hand, increased the WRP size resulted in increase in PUU-WRP composite’s shore hardness, compression permanent deformation, and ice adhesion force, while the tensile strength and contact angle were the opposite. The surface of the PUU-WRP composite material was hydrophobic, and the maximum contact angle was 102.3°. The reduction of WRP particle size and dosage was beneficial for reducing the ice adhesion force on the surface of PUU-WRP composite materials. The maximum interfacial shear and tensile strength of PUU-WRP composite material were 1.082 MPa and 0.244 MPa, respectively. After 42 days of UV aging, the maximum attenuation rate did not exceed 30 %. After the immersion test, the tensile strength attenuation of PUU-WRP composite material was basically controlled within 10 %. Finally, based on the fuzzy comprehensive evaluation (FCE) method, it was recommended to use WRP with a particle size of 0.6 mm and a dosage of 30 wt%-40 wt%.
•A filling material for active ice-breaking in asphalt pavement grooves has been developed.•The compression permanent deformation at −20℃ of PUU-WRP composite materials was evaluated.•The UV aging resistance and hydrolysis resistance of PUU-WRP composite materials were verified.•The optimal ratio for comprehensive performance of PUU-WRP composite materials was determined.
The seamless asphalt plug expansion joint integrates a traditional asphalt plug joint (APJ) with an overlying continuous asphalt concrete layer, preventing block failure of the asphalt plug joint and ...enhancing driving comfort. However, typical damages such as fatigue cracking, rutting, and permanent deformation often occur in the upper asphalt layer. This is attributed to the inadequate stiffness of the lower joint plug mastic, particularly under high temperatures and heavy loads. To extend the service life of asphalt plug expansion joints under such conditions and enhance their durability, efforts were made to bolster the performance of the lower asphalt plug joint mixture and improve anti-rutting performance. This study involved: (1) Qualifying APJ mixture requirements under high temperature and heavy load by focusing on two critical material properties: good rutting resistance and permanent deformation resistance. High temperature rheological properties of these binders were examined through temperature scanning tests and multi-stress creep recovery tests (MSCR). (2) Exploring the impact of binder-aggregate ratios and specimen molding methods (standard compaction, paving vibration and pre-mixing) on the bonding strength and rutting resistance of the APJ mixture. This analysis was conducted using pull-off tests and dynamic stability tests. (3) Development of a novel APJ featuring dowel bars to enhance vertical deflection resistance and joint horizontal movement. Comprehensive laboratory tests showcased the modified joint structure's resilience after numerous test cycles, demonstrating exceptional resistance to bending and vertical deformation. The significant findings from this research provide valuable insights for optimal material selection, appropriate joint design, and installation guidelines for seamless asphalt plug expansion joints.
Warm mix asphalt (WMA) is a new technology which asphalt mix is produced and placed at normal temperature. It has advantages including low cost, environmentally friendly, haul-convenience, and so on. ...WMA has been widely tested and applied in the USA in the last decade, but it has just started in China. Recently, a new WMA using a new plastic-macromolecule-normal temperature additive, which was called “SMC” by the production company, was introduced as asphalt modifier. Based on discussing the strength forming process of this new WMA with SMC, a series of laboratory tests, including Marshall stability test (MST), boiling test (BT), modified immersion Marshall test (MIMT), freeze-thaw splitting test (FTST), rutting test (RT), low-temperature bending test (LTBT), and abrasion loss test (ALT), were conducted in this study to assess the performance of this WMA and the capability of applying it on low volume roads in China. SMC modified asphalt mixed under normal temperature is used in testing samples. It was found that this WMA product exhibited merits on its strength, which was about 6.7 kN bigger than the requirement of 5.0 kN in the JTG F40-2004, on high-temperature stability, which is about 1100 times/mm greater than the requirement of 600–1000 times/mm in the JTG F40-2004, and on its storage stability. Based on these indicators, it is recommended that this product could be used for low volume low class roads construction. However, due to the relatively lower water resistance and low-temperature cracking resistance, this product is suggested to be applied first in the areas with warm weather and little rainfall. In order to improve the performance of this WMA with SMC, further research on this SMC asphalt modifier should be continued.
This study explored the effect of interface morphology on interlayer bonding in asphalt pavements, addressing existing challenges in its consistent characterization. The research aimed to develop a ...comprehensive indicator system for the characterization of interfacial morphology within double-layered asphalt constructs, thereby providing deeper insight into its impact on bonding strength. The methodology involved preparing specimens from three typical asphalt mixtures – dense-graded asphalt concrete (AC), stone mastic asphalt (SMA), and open-graded friction course (OGFC) – and analyzing their interlayer surfaces using a novel non-destructive technique alongside 3D laser scanning. This led to the identification of 32 morphological indicators across two-dimensional (2D) and three-dimensional (3D) domains. The findings revealed a significant correlation between these indicators and interlayer shear strength, establishing a robust framework for linking interface morphology with interface bonding properties. The study highlights the relative stability of the lower interlayer surface's morphology compared to the variability observed in the upper surface, attributed to differences in grain size distribution and skeleton. This variability significantly influenced the morphological reconstruction of the lower surface. Through the application of the M(P) characterization method, critical morphological indicators that exhibit a strong association with interlayer shear bonding were identified, enhancing the understanding of the factors influencing bonding efficacy in asphalt pavement layers.
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•Introduced a new characterization appraoch of interface morphology in bilayered asphalt systems.•Analyzed interface point clouds, 2D/3D features, introducing M(P) characterization method.•Identified 10 comprehensive, 7 independent indicators correlating with interface shear strength.•Developed a robust interfacial morphology indicator system based on bonding strength.
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