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The salt erosion environment will lead to the deterioration of asphalt pavement performance and seriously restrict the service life and sustainability of asphalt pavement. In this research, the evolution mechanism of asphalt performance induced by chloride salt erosion was explored by atomic force microscopy (AFM) and molecular dynamics (MD) simulation from the nanoscale. The AFM test results demonstrated that with increasing chloride salt concentration and erosion time, the adhesion force, adhesion energy, surface free energy, and dissipated energy of asphalt binder decreased significantly. The fitted modulus of the four contact mechanics models all decrease with increasing chloride erosion time. It is recommended to use the Cone Sphere or Johnson-Kendall-Roberts (JKR) model to fit the Young's modulus of asphalt binder. The MD simulation results show that the tensile strength and shear strength of asphalt binder in the three directions decreased after chloride salt erosion, and there are differences in the magnitude of reduction in different directions. Chloride salt erosion not only inhibits the translational migration behavior of SARA fractions [saturates (S), aromatics (A), resin (R), and asphaltenes (A)] but also limits the rotational migration behavior. Although chloride salt erosion has little effect on the aggregation behavior of asphaltene, it still affects the degree of molecular entanglement of SARA fractions. The distribution of asphalt molecules becomes heterogeneous after chloride salt erosion. This research not only presents the erosion damage mechanisms of the asphalt binder but also helps to promote the sustainability of the asphalt pavements exposed to a chloride salt environment. [ABSTRACT FROM AUTHOR]

This paper has proposed a closed-form solution for two-dimensional (2D) plane strain consolidation in unsaturated soils with lateral and vertical semipermeable drainage boundaries under time-dependent loading. By using the eigenfunction expansion technique, the governing equations are expanded into coupled ordinary differential equations, and the final solution of pore pressures is obtained by the integral transform method. The degraded proposed solution is then verified with the existing solution. The results show full agreement with the solutions, which indicates the proposed solution and program are completely correct. Meanwhile, the comparison between the analytical solutions and the finite-element simulations also demonstrates the correctness of the proposed solution. Subsequently, the effect of semipermeable parameters and loading parameters on the consolidation behavior has been investigated through the obtained analytical solution. And the distribution of consolidation profiles along two different directions has also been studied. It can be concluded that time-dependent loading changes the dissipation process obviously compared with constant loading. As the soil above the water table line is unsaturated, when constructing structures (e.g., houses and highways) on unsaturated soft soil, assessing the joint deformation of the structure and the foundation soil is essential to prevent excessive settlement and perhaps even cracking of the structures. When constructing on this soil, the foundations are often treated by some measures to avoid settlement and cracking. For example, vertical drains are used to accelerate the consolidation of the foundation soil. However, the presence of factors that impede drainages, such as the well resistance effect and the smear effect, brings some difficulties in calculating the coordinated deformation of the structure and the foundation soil. To integrate the effects of these factors, the research in this paper provides an analytical solution to evaluate the coordinated deformation of buildings and unsaturated soil. The analytical model can provide guidance for the construction of structures on such foundations by taking into account the unsaturated soil, the impeded drainage boundary, and the construction process. [ABSTRACT FROM AUTHOR]

The type of the manufacturing technology as well as the reduced production temperatures of warm mix asphalt (WMA) always raise controversy about the early life and long-term performance of WMA mixtures, more specifically concerning the resistance to stripping, permanent deformation, and fatigue cracking. The present paper is primarily oriented to evaluate such major controversial aspects of WMA moisture, rutting, and fatigue-cracking susceptibility. For this purpose, an experimental campaign and indices were developed to discern the properties among WMA systems in comparison to reference hot mix asphalt (HMA) system. The bonding strength (BS) test was developed to quantify the unconditioned and conditioned failures at the adhesive scale. In addition, the evolutions of the mechanical damage and air voids of asphalt mixtures under the effects of multiple freeze–thaw cycles (FTCs), were evaluated. The rutting susceptibility of mixes was assessed using a developed measure, namely, strain index (SI), which is based on strain/deformation results of the creep-recovery test. Continuous and intermittent fatigue tests were employed to determine fatigue life as well as the healing potential of the mixes. The zeolite-, wax-, and chemical-based WMA technologies provided comparable-to-better BS when compared with the HMA systems. Based on the results of unconditioned and retained tensile strength after multiple FTCs, moisture-induced degradation showed that HMA mixes can withstand more FTCs than WMA mixes. The results of SI indicated that the zeolite WMA produced at low temperature is more susceptible to rutting performance (i.e., lower SI), however the chemical-based mixtures are on par with that of HMA, but wax-based additive is more beneficial to mitigate such distress. The unfavorable influence of reduced production temperature (from 145°C to 120°C) was distinguishable for the rutting results only. The three WMA products produced asphalt mixes at reduced temperatures with better or comparable fatigue life. Using the intermittent fatigue tests, both the hot and warm mixes showed better healing efficiency. [ABSTRACT FROM AUTHOR]

The dynamic response of heterogeneous deep-sea sediments under moving nonuniform mining collector loading was determined analytically. The heterogeneity of deep-sea sediments is associated with the elastic modulus increasing nonlinearly with depth. The ground pressure of the mining collector with longitudinal eccentricity was assumed to have a trapezoidal distribution. The complex Fourier series method was used to expand the soil displacement and the loading function of the ground pressure with eccentricity. Thus, the governing partial differential equations (PDEs) of motion for the soil were reduced to ordinary differential equations (ODEs) with respect to the horizontal direction x and the time t. The analytical solution of the ODEs was solved by the method of Frobenius. After verifying the analytical solution by means of comparisons with the Abaqus simulated results for the special cases of homogeneity under uniform load, this analytical solution was utilized to assess the effect of heterogeneity, eccentricity, and pedrail length on the response of deep-sea sediments. [ABSTRACT FROM AUTHOR]

Estimating pavement internal forces due to the swelling or shrinking of expansive soils is of vital importance for planning, design, and construction. Such efforts can minimize some possible damage due to expansive soils during pavement services. This study extends an analytical model on the single-layer Euler–Bernoulli beam resting on the Winkler foundation to estimate pavement internal forces in the multilayer pavement structure. Besides, an improved efficient algorithm is proposed in this paper for computing the value of virtual load parameters. The proposed closed-form solution and iterative algorithm are then verified by comparing the degraded solution with the single-layer beam model and the existing iterative algorithm. The influences of the beam model (single layer or multilayer) and foundation parameters on the pavement internal forces have also been investigated through parametric studies. Furthermore, the computational efficiency is compared between the iterative algorithm adopted by the previous researcher and the iterative algorithm proposed in this paper. It can be seen that a single-layer beam model may underestimate pavement internal forces induced by expansive soils. Foundation parameters will affect the value of virtual load parameters. Also, it can be found that the iterative algorithm proposed in this paper can reduce the iterative calculation time considerably. Moreover, it can be observed that with more fitting points and fitting terms, the fitting has a more accurate effect, and the advantages of using the iterative algorithm proposed in this paper are more pronounced. [ABSTRACT FROM AUTHOR]

The road pavement is a typical three-dimensional (3D) multilayered half-space medium, which consists of the surface courses, base courses, and soil subgrade/foundation. It is critical to understand the dynamic response of the road pavement under vehicular loads for improving structural design efficiency. The actual vehicular loads can be simulated as a harmonic moving load. In general, there are several methods to analyze the dynamic response of the multilayered half-space medium under harmonic moving loads, such as the boundary element method (BEM) and the finite-element method (FEM). However, the previously mentioned methods might face some unavoidable problems, for example, the numerical overflow, when the thickness of the medium is thicker, which causes the wrong result or long computing time. Therefore, the objective of this study is to develop a precise solution to solve the dynamic response of the 3D multilayered half-space medium under a harmonic moving load. In this study, a new type of 3D spectral element method (SEM) was developed and applied to the dynamic response analysis. Details of the mathematical derivation, implementation, and verification were demonstrated in the current paper. Subsequent numerical results, based on a layered road pavement structure constructed on a soil foundation, indicated that both the load speed and the frequency, the damping ratio of the structural materials, and the interlayer condition significantly impacted on the dynamic response of the structure under vehicular loads. [ABSTRACT FROM AUTHOR]

The effect of ethylene vinyl acetate (EVA) on the aging properties and rheological properties of rubberized asphalt was measured in this paper to identify the optimum proportion of EVA combined with waste tire rubber (WTR) modified asphalt. Aging methods of thin-film oven test (TFOT) and pressure aging vessel test (PAV) were conducted to imitate the different degrees of the aging process. At first, frequency sweep at different temperatures was carried out to construct the construction of G* master curves, following the time-temperature superposition principle, to evaluate the aging sensitivity. The black diagram was depicted to compare the rheological behavior of different asphalt binders. The calculation of the WLF equation based on the shift factor of master curves was conducted to calculate the values and aging index of 15°C DSRFn to assess the resistance to fatigue cracking at the intermediate temperature. Then, zero shear viscosity (ZSV) and rutting factor (G*/sinδ) at 60°C were also used to calculate the aging index, because these both are measurements of resistance to rutting deformation at high temperature. Finally, the microstructure of unaged and aged asphalt binder was studied by Fourier transform infrared spectroscopy (FTIR). The relationship between rheological and chemical indexes was studied. The results show that 15%WTR+4%EVA has the best antiaging performance, and EVA can reduce the aging sensitivity of different parameters, especially in the high-temperature area. [ABSTRACT FROM AUTHOR]