Jianzhong Pei

Development and Validation of Viscoelastic-Damage Model for Three-Phase Permanent Deformation of Dense Asphalt Mixture

AbstractPermanent deformation of asphalt mixture under repeated load can be divided into three phases: decelerating phase, stationary phase, and accelerating flow phase. Most of the existing models cannot fully describe deformation characteristics during the three phases. In this paper, the characteristics of three-phase permanent deformation are considered as the results of a competition between damage and hardening, in which a damage variable and a hardening variable are introduced to modify Burger’s model. First, the series-wound dashpot of the Burger’s model is modified by Usan’s hardening variable, and the undamaged viscoelastic properties are derived from rheological theory. Secondly, Kachanov’s equation for damage evolution is adopted to establish the constitutive model by using Lemaitre’s effective stress principle. Then a repeated load consisting of a haversine loading period and rest period is employed to simulate the actual vehicle loading on the asphalt pavement. Third, a viscoelastic-damage m...

Evaluation indices of asphalt–filler interaction ability and the filler critical volume fraction based on the complex modulus

The asphalt–filler interaction plays a significant role in the performances of asphalt mastics and mixtures, and the asphalt–filler interaction ability could be evaluated by the rheological properties. In this paper, two kinds of matrix asphalt binders and six kinds of fillers were selected to prepare asphalt mastic with different filler volume fractions, and the dynamic shear rheological properties of asphalt mastics were measured and analysed. The filler critical volume fraction which is the transition point from “diluted region” to “concentrated region” for asphalt mastic was defined and determined according to the variation of asphalt mastic’s complex modulus with filler volume fractions. In the “diluted region”, the asphalt–filler interaction plays a dominant role in the increasing of complex modulus. However, the interaction between filler particles plays a dominant role in the “concentrated region”. Then, the complex modulus coefficient ΔG*, the Einstein coefficient KE and the coefficient K−B−G* were applied to evaluate the asphalt–filler interaction ability in the range of the filler critical volume fraction. It indicated that the three evaluation indices had good consistency for characterising the asphalt–filler interaction ability, but the coefficient K−B−G* had the best sensitivity. So the coefficient K−B−G* can significantly distinguish the interaction ability between asphalt binder and different fillers.

Multiscale Validation of the Applicability of Micromechanical Models for Asphalt Mixture

Asphalt mixture is more complicated than other composite materials in terms of the higher volume fraction of aggregate particles and the viscoelastic property of asphalt matrix, which obviously affect the applicabilities of the micromechanical models. The applicabilities of five micromechanical models were validated based on the shear modulus of the multiscale asphalt materials in this paper, including the asphalt mastic, mortar, and mixture scales. It is found that all of the five models are applicable for the mastic scale, but the prediction accuracies for mortar and mixture scales are poorer. For the mixture scale, all models tend to overestimate at the intermediate frequencies but show good agreement at low and high frequencies except for the Self-Consistent (SC) model. The Three-Phase Sphere (TPS) model is relatively better than others for the mortar scale. The applicability of all the existing micromechanical models is challenged due to the high particle volume fraction in the multiscale asphalt materials as well as the modulus mismatch between particles and matrix, especially at the lower frequencies (or higher temperatures). The particle interaction contributes more to the stiffening effect within higher fraction than 30%, and the prediction accuracy is then deteriorated. The higher the frequency (or the lower the temperature) is, the better the model applicability will be.

Evaluation of asphalt–aggregate interaction based on the rheological properties

Abstract The silicon dioxide (SiO2) and calcium oxide (CaO) analytical reagents are selected to prepare asphalt mastics and the effects of aggregate chemical composition on asphalt–aggregate interactions (AAI) are evaluated based on the complex modulus and phase angle. It is found that the oxide analytical reagents significantly affect the rheological properties such as complex shear modulus and phase angle, and the effects of CaO are greater than SiO2 due to the stronger interaction between asphalt binder and CaO analytical reagents. Both the modulus stiffening ratio and the phase angle-based K. Ziegel-B coefficient could be used to evaluate the AAI, and the latter is the better index. Results show that the indexes increase with the test temperature, but decrease with the loading frequency, and tend to be constant. The higher adhesive strength between asphalt binder and limestone than basalt is likely attributed to the higher content of CaO in limestone aggregate and the stronger asphalt–CaO interaction.

Effect of Polymer Matrix on the Structure and Electric Properties of Piezoelectric Lead Zirconatetitanate/Polymer Composites

Piezoelectric lead zirconatetitanate (PZT)/polymer composites were prepared by two typical polymer matrixes using the hot-press method. The micromorphology, microstructure, dielectric properties, and piezoelectric properties of the PZT/polymer composites were characterized and investigated. The results showed that when the condition of frequency is 103 Hz, the dielectric and piezoelectric properties of PZT/poly(vinylidene fluoride) were both better than that of PZT/polyvinyl chloride (PVC). When the volume fraction of PZT was 50%, PZT/PVDF prepared by the hot-press method had better comprehensive electric property.

Effects of material characteristics on asphalt and filler interaction ability

ABSTRACT Asphalt and filler interaction plays a key role on the performances of asphalt mastics and mixtures, while the asphalt and filler interaction ability is in turn affected by the material characteristics. In order to analyse the effects of material characteristics on asphalt and filler interaction, two kinds of matrix asphalt binders and three kinds of fillers were used to prepare asphalt mastics with different filler volume fractions. The dynamic shear rheological properties of these asphalt mastics were measured. The evaluation index K–B–G * was calculated subsequently to analyse the effects of material characteristics on the asphalt and filler interaction ability. The results show that filler volume fraction, filler particle size, SiO2 content and asphalt components had various levels of effects on the asphalt and filler interaction ability. Variance analysis was then conducted to rank these influencing factors from high to low as: (1) filler particle size, (2) asphaltene and resins content, (3) filler volume fraction, and (4) SiO2 content.

Preparation and Photocatalytic Properties of TiO2-Al2O3 Composite Loaded Catalysts

This paper presents an experimental approach to study catalytic effects of Fe3+ modified nanometer titanium dioxide (TiO2) loaded on aluminium oxide (Al2O3). Sol-gel method was used to prepare modified TiO2 loaded on carrier. Purification tests were conducted in a self-developed instrument to study catalytic effects of TiO2 loaded on Al2O3 with different contents through degradation rate. The modification mechanism was studied by scanning electron microscope (SEM). Results showed that loading on Al2O3 improved photocatalytic effect of TiO2 modified with Fe3+. The best photocatalytic effect was achieved under catalytic action of Al2O3 loaded with 10% TiO2 composite; the degradation rates were 6.9%, 13.8%, 21.4%, and 49.2%, respectively, 0.7%, 3.9%, 1.3%, and 15.1% larger than unloaded TiO2. SEM results of four catalysts showed that nanometer TiO2 was coated in form of grain on the surface of Al2O3. The optimal loading content was 10% at which the nanometer TiO2 grains were coated on the surface of Al2O3 uniformly.

Molecular Dynamics Simulation to Investigate the Interaction of Asphaltene and Oxide in Aggregate

The asphalt-aggregate interface interaction (AAI) plays a significant role in the overall performances of asphalt mixture, which is caused due to the complicated physicochemical processes and is influenced by various factors, including the acid-base property of aggregates. In order to analyze the effects of the chemical constitution of aggregate on the AAI, the average structure C65H74N2S2 is selected to represent the asphaltene in asphalt and magnesium oxide (MgO), calcium oxide (CaO), aluminium sesquioxide (Al2O3), and silicon dioxide (SiO2) are selected to represent the major oxides in aggregate. The molecular models are established for asphaltene and the four oxides, respectively, and the molecular dynamics (MD) simulation was conducted for the four kinds of asphaltene-oxide system at different temperatures. The interfacial energy in MD simulation is calculated to evaluate the AAI, and higher value means better interaction. The results show that interfacial energy between asphaltene and oxide reaches the maximum value at 25°C and 80°C and the minimum value at 40°C. In addition, the interfacial energy between asphaltene and MgO was found to be the greatest, followed by CaO, Al2O3, and SiO2, which demonstrates that the AAI between asphalt and alkaline aggregates is better than acidic aggregates.

Enhancement of the dielectric performance of PA11/PVDF blends by a solution method with dimethyl sulfoxide

Abstract In this study, the solution method was used to prepare polyamide 11/polyvinylidene difluoride (PA11/PVDF) blend films. The crystal phase compositions and microstructures of the blends were studied by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy analysis. Additionally, the dielectric properties of the PA11/PVDF blends, with different ratios and concentrations, were tested. The results indicated that the solution method is more propitious in forming β crystals during the preparation of the PA11/PVDF blend films compared with the melt blending method. The amount of β crystals present in PVDF was dependent on the ratio of dimethyl sulfoxide (DMSO) and H2O. Specifically, for the 5:95 ratio of DMSO/H2O precipitants, the PA11/PVDF (80:20) blend films prepared by the solution method had a high dielectric constant of 188.1 and a dielectric loss of 1.37.

Effects of WMA Additive on the Rheological Properties of Asphalt Binder and High Temperature Performance Grade

Sasobit additives with different dosages were added into 70# and 90# virgin asphalt binders to prepare WMA binders. The rheological properties, including and δ, were measured by using DSR at the temperature ranging from 46°C to 70°C, and the effects of temperature, additive dosage and aging on , critical temperature, and H-T PG were investigated. The results indicate that WMA additive improves but reduces δ, and the improvement on 70# virgin binder is more significant. exponentially decreases with the increasing temperature but linearly increases with the increasing additive dosage. Aging effect weakens the interaction between binder and additive but significantly increases the binder’s viscosity; that is why is higher after short-term aging. In addition, the critical temperature increases with the increasing additive dosage, and the additive dosage should be more than 3% and 5% to improve H-T PG by one grade for 70# and 90# virgin binder, respectively.