Hai Viet Vo

Asphalt Mixture for the First Asphalt Concrete Directly Fastened Track in Korea

The research has been initiated to develop the asphalt mixtures which are suitable for the surface of asphalt concrete directly fastened track (ADFT) system and evaluate the performance of the asphalt mixture. Three aggregate gradations which are upper (finer), medium, and below (coarser). The nominal maximum aggregate size of asphalt mixture was 10 mm. Asphalt mixture design was conducted at 3 percent air voids using Marshall mix design method. To make impermeable asphalt mixture surface, the laboratory permeability test was conducted for asphalt mixtures of three different aggregate gradations using asphalt mixture permeability tester. Moisture susceptibility test was conducted based on AASHTO T 283. The stripping percentage of asphalt mixtures was measured using a digital camera and analyzed based on image analysis techniques. Based on the limited research results, the finer aggregate gradation is the most suitable for asphalt mixture for ADFT system with the high TSR value and the low stripping percentage and permeable coefficient. Flow number and beam fatigue tests for finer aggregate asphalt mixture were conducted to characterize the performance of asphalt mixtures containing two modified asphalt binders: STE-10 which is styrene-butadiene-styrene (SBS) polymer and ARMA which is Crum rubber modified asphalt. The performance tests indicate that the STE-10 shows the higher rutting life and fatigue life.

Evaluation of Asphalt Mixture Modified with Graphite and Carbon Fibers for Winter Adaptation: Thermal Conductivity Improvement

AbstractConventional asphalt concrete is relatively low conductive. This paper focus on the improvement of thermal properties of asphalt mixtures using conductive fillers, and investigating the conduction performance by two-dimensional (2D) simulation. Also, the microstructure of asphalt mixture was analyzed with extremely high magnification to observe the distribution of conductive fillers in the mixture. Indirect tensile (IDT) strength was additionally investigated. Different asphalt mixtures used in this study was modified with milled carbon fiber, chopped carbon fiber, and graphite powder. The study also evaluated the effect of mixed fillers combined carbon fiber with varying admixtures of graphite contents. The thermal properties of modified asphalt mixtures were measured and calculated to evaluate their conduction effects to obtain the appropriate kind and quantity of carbon fibers and graphite. Based on the results of thermal properties of the asphalt mixtures, the 2D simulation was performed on a ...

Thermal properties of asphalt mixtures modified with conductive fillers

This paper investigates the thermal properties of asphalt mixtures modified with conductive fillers used for snow melting and solar harvesting pavements. Two different mixing processes were adopted to mold asphalt mixtures, dry- and wet-mixing, and two conductive fillers were used in this study, graphite and carbon black. The thermal conductivity was compared to investigate the effects of asphalt mixture preparing methods, the quantity, and the distribution of conductive filler on thermal properties. The combination of conductive filler with carbon fiber in asphalt mixture was evaluated. Also, rheological properties of modified asphalt binders with conductive fillers were measured using dynamic shear rheometer and bending beam rheometer at grade-specific temperatures. Based on rheological testing, the conductive fillers improve rutting resistance and decrease thermal cracking resistance. Thermal testing indicated that graphite and carbon black improve the thermal properties of asphalt mixes and the combined conductive fillers are more effective than the single filler.

Simulation of snow melting pavement performance using measured thermal properties of graphite-modified asphalt mixture

Chemical melting agents are traditional methods for snow-removing applications. Due to their adverse environmental impact, thermo-snow melting pavements with conductive fillers are becoming frequently used. In this study, the thermo-physical properties of graphite-modified asphalt mixtures (GMAM) and the sensitivity of snow melting pavements were investigated. The microstructure of GMAM was analysed at extremely high magnification to observe the distribution of conductive fillers in the mixture. Two different mixing processes were adopted to mould asphalt mixtures: dry mixing and wet mixing. The conductivity was compared to evaluate the effects of asphalt mixture preparing methods and the quantity of graphite on the thermal properties of GMAM. A one-dimensional finite difference analysis was performed to determine the efficiency of GMAM for snow melting processes. Microstructure analysis was conducted on scanning election microscope (SEM) images of the fractured surface of specimens. Thermal testing and analysis results indicated that graphite improves the conductivity of asphalt mixtures and shortens the time required for snow melting. The numerical analysis results showed that environmental factors have significant effects on pavement surface temperature, and adjusting the heat source temperature can substitute the changes in environmental conditions. According to the micro-analysis, graphite particles form clusters throughout the asphalt mixture.

Application of Conductive Materials to Asphalt Pavement

Snow-melting pavement technique is an advanced preservation method, which can prevent the forming of snow or ice on the pavement surface by increasing the temperature using an embedded heating system. The main scope of this study is to evaluate the impact of conductive additives on the heating efficiency. The electrical resistivity and thermal conductivity were considered to investigate effects of conductive additives, graphite, and carbon fibers on the snow-melting ability of asphalt mixtures. Also, the distribution of the conductive additives within the asphalt concrete body was investigated by microstructural imaging. An actual test was applied to simulate realistic heating for an asphalt concrete mixture. Thermal testing indicated that graphite and carbon fibers improve the snow-melting ability of asphalt mixes and their combination is more effective than when used alone. As observed in the microstructural image, carbon fibers show a long-range connecting effect among graphite conductive clusters and gather in bundles when added excessively. According to the actual test, adding the conductive additives helps improve snow-melting efficiency by shortening processing time and raising the surface temperature.

Lightweight Treated Soil As a Potential Sustainable Pavement Material

AbstractRecycling of poor soil becomes very important when good-quality construction materials are limited. This paper investigates the properties of lightweight treated soil such as strength properties based on the stress-strain behaviors, durability by simulating the freeze-thaw cycle (FTC), and evaluation of the road performance when lightweight treated soil was used as a subbase layer. Lightweight treated soil was made by mixing dredged soil waste, cement, air-foam, and water with the determined proportion. Test specimens were prepared with various cement contents and air-foam contents. Several series of unconfined compression tests, FTC tests, and thermal conductivity tests were then conducted. From the results of the experiments, it is observed that the strength of lightweight treated soil increased with an increase in cement content, but decreased with an increase in air-foam content or number of FTCs. The thermal conductivity of lightweight treated soil decreases with increasing air-foam content. ...

Applications of Air-Foamed Stabilized Soil as Potential Subgrade Material of Railway Track

In these days, use of proper soils for construction materials become more limited, but wasted soils are abundant; therefore, the method which can use wasted soil such as soft clay has been investigated. Air-foamed stabilized soil has been used widely, but never been used as a subgrade material. The aim of this study is to verify the use of airfoamed stabilized soil as the subgrade construction material. Several wasted soils such as soft clay was selected to make air-foamed stabilized soil mixtures. The air-foamed stabilized mixture design was conducted to find the optimum quantity of stabilizing agent (cement) and air-foamed, and the effect of cement quantity and air-foamed quantity on strength of air-foamed stabilized soil mixtures base on the test results of unconfined compression test was investigated. As the quantity of cement is increased, the strength is increased, but the quantity of air-foamed is increased and the strength is decreased. Elastic moduli based on unconfined compression strength were obtained to use as subgrade of railway track design.

Recycling of Dredged Soil Waste Using Air-foam Stabilization Method as Highway Construction Material

Recycling of wasted soil becomes a hot issue due to the difficulty of disposal, whereas stiff soil is limited for construction. This paper investigates the properties of air-foam stabilized soil made from dredged soil recycled by air-foam stabilization method such as strength, resilient modulus, and evaluation of the pavement performance when using it as pavement sub-base material. Air-foam stabilized soil samples are prepared by mixing soil and water with various cement and air-foam contents. The unconfined compression test and the resonant column test are conducted; then, the relationship between the unconfined compressive strength and the resilient modulus of air-foam stabilized soil is evaluated. The resilient modulus values are applied in a layered elastic model to predict the allowable number of load repetitions based on fatigue cracking and rutting. According to the pavement performance, air-foam stabilized soil is sustainable and suitable in the role of pavement sub-base material.