Papers by Keyword: Asphalt Mixture

Abstract: Asphalt mixture is a kind of a viscoelastic material with viscoelastic characteristic of time-temperature equivalence. This paper, from the engineering practical consideration, and the perspective of time-temperature equivalence principle, based on the Rutting Test of Asphalt Mixture,has obtained equivalence relations of the effect of wheel speed and temperature on asphalt mixture rut index by different wheel speed and different temperatures rutting test, so as to provide the data support for the research of anti-rutting mechanism of asphalt pavement.

Abstract: The purpose of this paper is to describe (at micro-scale) the geogrid-reinforced flexible pavement behaviour under a static loading. The finite element technique is used to analyse the mechanical interaction between granular particles, asphalt binder and geogrid. The geogrid is the most commonly used geosynthetic product for enhancing the stiffness and stability of traditional flexible pavement and it is beneficial for reducing the rutting damage in pavement. The geosynthetic performance is influenced by geometry, material and its placement inside the pavement layers. Whereas, the asphalt mixture performance is governed by properties of aggregate (shape, size distribution, etc.), properties of asphalt binder (grading, viscosity, asphalt modifiers, etc.) and asphalt-aggregate interactions (adhesion and absorption, etc.). Through FEM software (ABAQUS) the microstructure is modelled in 3D. This microstructure is made up of three different components: spherical particles (aggregates), asphalt binder and one strip of geogrid.

Abstract: Flexible pavements deteriorate and crack with time due to the frequent traffic load imposed upon it. Many studies have been done to predict the effects of frequent traffic load and environmental conditions on pavements in the effort to find the best pavement design which resist deterioration and ensure longer pavement service time. This study investigates the effect of mixing asphalt with varying percentages of nano calcium carbonate (CaCO₃), namely 0, 2, 4, and 6 %. The mixtures were designed based on the Superpave mix design criteria. Investigation was done using several tests, namely resilient modulus, indirect tensile strength, moisture susceptibility, and dynamic modulus tests. Samples were subjected to aging to determine their resilient modulus. The results of the investigation show that resilient modulus and indirect tensile strength increased when higher percentages of nanoparticles were added to asphalt mixture, with improvement of 138 and 48.18% respectively. Modified binders showed up to 17% improvement in moisture susceptibility comparison to base asphalt mixture, while the result of dynamic modulus test showed that the stiffness of modified asphalt increased 76.69%. The investigation also found that adding 6% CaCO₃ nanoparticles to asphalt produced modified asphalt with the best performance. In addition, the results show that the modified asphalt with CaCO₃ is suitable for hot and humid regions (tropical countries) in the field of highways construction, as the modifier was able to mitigate the influences of high-temperature rutting and moisture damage.

Abstract: Fatigue, creep and erosion are among the factors which destroy the asphalt mixture and modifying the asphalt binder via additives such as crumb rubber, sulfur, carbon, as well as natural and synthetic polymers has been done in order to improve the strength of asphalt mixture. Knowledge in the field of nanotechnology along with its capability and attractiveness for application as nanoparticles in different industries such as asphalt industry has attracted great attention in recent years. In this study, specific percentages of TiO₂ nanoparticles, namely 2, 4, and 6, were added to the asphalt binder as the nanocomponent. Done physical common tests such as penetration degree, softening point, flash point and viscosity of the base asphalt binder and modified asphalt binder, the bending beam samples composed of origin asphalt sample and modified asphalt sample with 4% TiO₂ nanoparticle were subjected in different micro strains to fatigue loads. Results of four point bending fatigue test showed that the addition of TiO₂ nanoparticles to the asphalt binder increased the fatigue strength in the asphalt samples. Modified asphalt binder is stiffer, more viscous than original asphalt binder and due to TiO₂ nanoparticles more temperature tolerance and load bearing capacity, modified Asphalt is more resistant under fatigue loads.

Abstract: Effect of aging on physical properties of asphalt binder was studied. The relationship between degradation of the low temperature properties of asphalt binder and asphalt mixture was also investigated. After the thin film oven test (TFOT) with different aging time, the AH-70 binder and the SBS modified asphalt binder were used to prepared asphalt mixture samples. The binder was characterized using penetration, ductility and Beam Bending Rheometer (BBR), and the low temperature cracking resistance of asphalt mixture was studied by Three-point Bending Fracture (TBF). The correlation between different physical parameters of binder, as well as between different aging properties of the binder and asphalt mixture, was examined. The results showed that aging influenced binder physics significantly, and resulted in a decline in the properties of low temperature cracking resistance of asphalt mixture. Although, aging susceptibility of binder and asphalt mixture may be ranked differently when different evaluation methods ware used, a strong correlation was observed between the aging of binder and asphalt mixture.

Abstract: Deterioration of asphalt pavements by water immersion and increased moisture content, presents one of the principal issues for pavement technologists. Especially if concentrating on initial phases of the life-cycle of a pavement. Water in the form of rain precipitation and natural air moisture can be harmful to the bonds between bitumen and aggregate particles, which occurs through the medium deteriorated adhesion on the interface of those phases, or the overall deterioration of the adhesion. Even if it might look at the first glance that bituminous binder creates perfectly impermeable layer of particular aggregate particles, in reality the bitumen film makes unstable coating of aggregates in unequal thicknesses and frequencies. Those weakened areas are far more susceptible to water and moisture affects, which enter the asphalt layer on the boundary of aggregates and bituminous binder. To improve the adhesion between bitumen and aggregates and to get in general better functional characteristics of asphalt mixtures large number of available additives exists in civil engineering. First group can be defined as additives which are added directly to the bituminous binder and provides a kind of bitumen modification. Second group includes mineral additives, which may partially or completely replaced fine-grained particles, normally in the form of filler. In this article the objective was set to qualify effect of mechanically activated microfiller originating from limestone by-products or from recycled concrete as a substitute to fine-grained active filler in asphalt mixtures. The research targeted to utilize waste materials and to contribute to the reduction of overall negative impacts to the environment.

Abstract: The high temperature stability of AC-16, AC-13, AC-20 under specimen thickness of 5cm and 6cm is studied through indoor asphalt mixture high rutting test, Through comparison and analysis about experimental data, it is found that the stability of AC-16, AC-13, AC-20 asphalt mixture at high- temperature decreases in turn. It is shown that thickness changes did not affect the change trend of the high temperature stability under gradation change, and the stability of AC-16 at high-temperature is the best, the AC-13 is second and the AC-20 is less.

Abstract: In the areas of South China, the asphalt pavement will appear various forms of water damages under the condition of vehicle loads and humid rainy environment. The interface of between aggregate and asphalt is the weaknesses position of the mixture internal structure, which will impose a significant influence on the service life of asphalt mixtures. However, the existing mesomechanics models of asphalt mixtures are almost based on the three-phase composite materials (asphalt mortar, aggregate, void) and have no enough consideration for the actual mechanics characteristics of the weak interface. It is no doubt that the effectiveness of the numerical simulation results will face a great challenge. The main purposes of this paper is to analyze and summary the relative basic characteristics of asphalt-aggregate interface including interface contact behavior, microstructure characterization methods, interface damage features and the macro-micro quantitative evaluation method of the interface damage The results show that the existing mechanical model ignores the asphalt-aggregate interface imperfect bonding, which make the asphalt-aggregate interface mechanical properties difficult to be perceived. Therefore, establishing a more rational micromechanical analysis model to predict asphalt macroscopic mechanical properties of asphalt mixtures will certainly be an urgent task and will provide a theoretical and scientific support for the optimization of asphalt mixture design.

Abstract: In this paper a micro-scale model to investigate the structural integrity of a runway surface has been developed. By performing stress analysis on a representative volume element (RVE), our model specification has been focalized on two elementary mixture constituents, two rigid components glued together by asphalt. The analysis is performed under thermo-mechanical actions, as those produced by landing gear impact and variable high surface temperatures. Three different interfaces (rigid to rigid, rigid to soft and soft to soft), three different asphalt density and two different values of surface temperature have been considered in the simulation. Resulting stress and strain fields are compared to define the greater critical conditions and to evaluate the micro-scale structural integrity

Abstract: This paper deals with the use of special asphalt-rubber mixture, the Stress Absorbing Layer (SAL). Description of SAL and test methods is given in theoretical part of this paper. Several different mixtures were designed and selected ones subsequently tested. Low-temperature properties, rutting test, bending tensile relaxation, stiffness modulus and fatigue properties were determined. These parameters are stated for asphalt-rubber mixtures with aggregate sizes up to 5 mm, 8 mm or 16 mm.