High modulus asphalt concrete: A state-of-the-art review

To obtain the viscoelastic parameters of asphalt mixtures and analyze the effect of temperatures and modifiers on viscoelastic properties of asphalt mixtures, the creep compliances of the neat asphalt mixture (AM), compound diatomite and basalt fibers reinforced asphalt mixture (DBFAM), and styrene-butadiene-styrene modified asphalt mixture (SBSAM) were tested and calculated by the static creep tests. And the creep compliances of the three asphalt mixtures at −20 °C, −10 °C, and 0 °C are deducted by the time–temperature equivalence principle (TTEP) and Arrhenius equation. Further, the relaxation modulus of the three asphalt mixtures from −20 °C to 50 °C at 10 °C increments are calculated by the convolution integral and Simpson method. Subsequently, the Burgers model, the generalized Kelvin model, and the generalized Maxwell model are applied to analyze the viscoelastic properties of the three asphalt mixtures at different temperatures. The results show that the generalized Kelvin model and the generalized Maxwell model are superior to the Burgers model in describing the variation of viscoelastic properties of asphalt mixtures with loading time. At low temperatures, asphalt mixtures have excellent properties in resisting permanent deformation and releasing internal stress. Besides, the addition of SBS modifier and compound diatomite and basalt fibers modifier can significantly raise the viscosity η1 and the elastic modulus E1 of the asphalt mixture, respectively.

Viscoelastic Properties of Asphalt Mixtures with Different Modifiers at Different Temperatures Based on Static Creep Tests

Optimization of the formation of coatings based on SiAlOC glasses via structural, microstructural and electrochemical studies

To optimize the properties of asphalt mixtures and make full use of waste rubber tires, diatomite and crumb rubber particles were applied to reinforce the asphalt mixtures in this study. The rutting tests, the three-point bending tests, the freeze-thaw splitting tests, and the uniaxial compression creep tests were performed to analyze the effects of asphalt types and aggregate gradation on the pavement properties of diatomite and crumb rubber particles reinforced asphalt mixtures (DRPAM). Subsequently, the creep and relaxation characteristics of DRPAM were analyzed by the Burgers model, the modified Burgers model, the second-order extensive Maxwell model, and the Scott–Blair model. The results show that rubber particles and diatomite can reinforce the high temperature, low temperature, and viscoelastic properties of asphalt mixtures, although the improvement effect is weaker than styrene-butadiene-styrene (SBS). Consequently, it is concluded that rubber particle and diatomite compound modified asphalt mixture with suspension dense gradation and SBS binder will have better performance.

Study on Mechanical and Viscoelastic Properties of Asphalt Mixture Modified by Diatomite and Crumb Rubber Particles

Characterization of dynamic response of asphalt pavement in dry and saturated conditions using the full-scale accelerated loading test

In order to represent the mechanical response laws of high-modulus asphalt pavement (HMAP) faithfully and objectively, the viscoelasticity of high-modulus asphalt mixture (HMAM) was considered, and the viscoelastic mechanical responses were calculated systematically based on moving load by numerical simulations. The performances of the HMAP in resistance to the deformation and the cracking at the bottom layer were compared with the ordinary asphalt pavement. Firstly, Lubao and Honeywell 7686 (H7686) were selected as the high modulus modifiers. The laboratory investigations of Asphalt mix-70 penetration, Asphalt mix-SBS (styrene-butadiene-styrene), HMAM-Lubao and HMAM-H7686 were carried out by dynamic modulus tests and wheel tracking tests. The conventional performances related to the purpose of using the HMAM were indicated. The master curves of the storage moduli were obtained and the viscoelastic parameters were fitted based on viscoelastic theories. Secondly, 3D pavement models based on moving loads for the viscoelastic structures were built using the non-linear finite element software ABAQUS. The wheel path was discretized in time and space to apply the Haversine wave load, and then the mechanical responses of four kinds of asphalt pavement were calculated. Finally, the sensitivity analysis was carried out. The results showed that the addition of the high modulus modifiers can improve the resistance to high-temperature rutting of the pavements. Except for the tensile strain and stress at the bottom of the underlayer, other responses decreased with the increases of the dynamic moduli and the change laws of the tensile strain and stress were affected by the range of the dynamic modulus. The tensile stress at the bottom of the asphalt layer would be too large if the modulus of the layer were too large, and a larger tensile strain would result. Therefore, the range of the modulus must be restricted to avoid the cracking due to excessive tension when using the HMAM. The resistance of the HMAP to deformation was better and the HMAP was less sensitive to load changes and could better withstand the adverse effects inflicted by heavy loads.

Viscoelastic Mechanical Responses of HMAP under Moving Load.

During rainfall, asphalt pavement structure layers are often not saturated. To study the dynamic response of unsaturated permeable asphalt pavement under moving load, 3-D finite element models for asphalt pavements with coupling of water–air–force were built based on unsaturated seepage theory. The vertical stress, the transverse stress, and the pore-water pressure, the vertical displacement responses of the asphalt pavement under moving loads were investigated. In addition, the results were compared and analyzed with that of the saturated permeable asphalt pavement. The results showed that the maximum transverse stress of the unsaturated asphalt pavement was about 200 kPa, while the saturated asphalt pavement was about 300 kPa. It is showed that the discharge of water has a great effect on avoiding cracks in the pavement. The maximum pore-water pressure of the unsaturated asphalt pavement is 56.67 kPa, and that of the saturated asphalt pavement decreases by 40.70 % in the same condition. The change of displacement in the area near the upper layer is more remarkable, and the maximum displacement of the saturated asphalt pavement is less than that of the unsaturated asphalt pavement. The vertical stress, transverse stress and pore-water pressure of the unsaturated asphalt pavement are smaller than saturated asphalt pavement. The asphalt pavement is prone to structural damage such as fatigue cracking and pit slot by dynamic water scouring when it is saturated condition. Therefore, the drainage inside the pavement is very important for the service life of the asphalt pavement. It ensures the asphalt pavement is unsaturated during rainfall. In future road construction, more permeable pavements should be considered.

Dynamic response characteristics of permeable asphalt pavement based on unsaturated seepage

To study the dynamic response of saturated asphalt pavement under moving load and temperature load, 3-D finite element models for asphalt pavements with hydro-mechanical coupling and thermal-hydro-mechanical coupling were built based on the porous media theory and Biot theory. First, the asphalt pavement structure was considered as an ideal saturated fluid⁻solid biphasic porous medium. Following this, the spatial distribution and the change law of the pore-water pressure with time, the transverse stress, and the vertical displacement response of the asphalt pavement under different speeds, loading times, and temperatures were investigated. The simulation results show that both the curves of the effective stress and the pore-water pressure versus the external loads have similar patterns. The damage of the asphalt membrane is mainly caused by the cyclic effect of positive and negative pore-water pressure. Moreover, the peak value of pore-water pressure is affected by the loading rate and the loading time, and both have positive exponential effects on the pore-water pressure. In addition, the transverse stress of the upper layer pavement is deeply affected by the temperature load, which is more likely to cause as transverse crack in the pavement, resulting in the formation of temperature cracks on the road surface. The vertical stress at the middle point in the upper layer of the saturated asphalt pavement, under the action of the temperature load and the driving load, shows a single peak.

https://www.mdpi.com/1996-1944/12/6/959/pdf

Study on Dynamic Response Characteristics of Saturated Asphalt Pavement under Multi-Field Coupling.

The profile of the inrun is crucial in ski jumping. With the development of technology, a considerable number of geometric lines have been proposed from a mathematical perspective and applied to the inrun. The third power function is the latest standard design of the transition zone profile proposed by the International Ski Federation (FIS). Therefore, the transition zone profile (third power function) was studied. The research on athlete’s force states can help make the profile better meet the competition requirements. The dynamic differential equations of the athlete were first obtained by considering air resistance and skiing friction. Mathematica was used to solve the equations, and the skiing velocity of the athlete at each structural point was obtained. Meanwhile, the skiing velocity of the athlete at the arc and the third power function were compared with the force. The results show that, under the condition that the length and height of the inrun are the same, there is no difference in the athlete’s skiing velocity. By comparing the athlete-exerted forces under two types of profiles, it was found that the third power function will make the athlete-exerted forces slowly increase without instantaneously raising the point of the arc, which is conducive to the maintenance of the athlete’s movement. It was shown that the third power function has a great advantage in controlling the reaction force of the athlete. Therefore, the inrun with a third power function in the transition zone is more conducive to the athlete’s skiing, which further improves the level of competition and optimizes the original inrun system. It can provide theoretical support for the application of the geometric profile of the ski jumping inrun at the Beijing Winter Olympic Games.

Rui Guo

Papers

Viscoelastic Mechanical Responses of HMAP under Moving Load.

Dynamic response characteristics of permeable asphalt pavement based on unsaturated seepage

Study on Dynamic Response Characteristics of Saturated Asphalt Pavement under Multi-Field Coupling.

Research on the inrun profile optimization of ski jumping based on dynamics

Ice material properties of ski jumping inruns