Ling Pang

Laboratory Study on Ultraviolet Radiation Aging of Bitumen

The effects of ultraviolet (UV) radiation on degradation of bitumen have received much attention from both academic and industrial points of view. However, quantitative evaluations of bitumen photo-oxidation in pavements have apparently not been determined. In this study, the effects of photo-oxidation of bitumen were investigated by exposing pressed thin films of bitumen. The data for thermal aging only were compared with corresponding data for photo-oxidation from exposure to UV radiation. The levels of aging were evaluated by following increases in the carbonyl functional group, and increases in viscosity. The results indicated that both thermal and UV aging occurred during exposure in the UV radiation oven test for thin bitumen films of both unmodified and SBS-modified bitumen. UV aging had a significant effect on bitumen properties, particularly when the bitumen film thickness was less than 150 μm. Results also showed that the level of UV irradiation intensity had a significant influence on the level of photo-oxidation of the bitumen.

UV and Thermal Aging of Pure Bitumen-comparison Between Laboratory Simulation and Natural Exposure Aging

ABSTRACT In this paper, several indoor laboratory aging tests and the Natural Exposure Aging (NEA) test were employed as the aging regimes of pure bitumen. The properties of various aged bitumen specimens were investigated by Dynamic Shear Rheometer (DSR) and Fourier Transform Infrared Spectra (FTIR). By this means the differences between the laboratory and natural exposure aging was analysed. Experimental results showed that both thermal and ultraviolet (UV) radiation aging happened during UV radiation oven test and the later was much more prominent on the influence of bitumens properties, in particular, when the binder films was smaller than 100 μm. In a wide range of frequency, complex modulus and phase angle obtained from DSR tests revealed that UV radiation oven test showed a better corresponding relationship with NEA when compared to Pressure Aging Vessel (PAV).

Fatigue Properties of Layered Double Hydroxides Modified Asphalt and Its Mixture

This study investigated the influence of layered double hydroxides (LDHs) on the fatigue properties of asphalt mixture. In this paper, different aging levels (thin film oven test (TFOT) and ultraviolet radiation aging (UV aging for short)) of bitumen modified with various mass ratios of the LDHs were investigated. The TFOT and UV aging process were used to simulate short-term field thermal-oxidative aging and long-term field light UV aging of bitumen, respectively. The influences of LDHs on the fatigue properties of LDHs were evaluated by dynamic shear rheometer (DSR) and indirect tensile fatigue test. Results indicated that the introduction of LDHs could change the fatigue properties of bitumen under a stress control mode. The mixture with modified bitumen showed better fatigue resistance than the mixture with base bitumen. The results illustrated that the LDHs would be alternative modifiers used in the bitumen to improve the lifetime of asphalt pavements.

The Utilization of Graphene Oxide in Traditional Construction Materials: Asphalt

In the advanced research fields of solar cell and energy storing materials, graphene and graphene oxide (GO) are two of the most promising materials due to their high specific surface area, and excellent electrical and physical properties. However, they was seldom studied in the traditional materials because of their high cost. Nowadays, graphene and GO are much cheaper than before with the development of production technologies, which provides the possibility of using these extraordinary materials in the traditional construction industry. In this paper, GO was selected as a nano-material to modify two different asphalts. Then a thin film oven test and a pressure aging vessel test were applied to simulate the aging of GO-modified asphalts. After thermal aging, basic physical properties (softening point and penetration) were tested for the samples which were introduced at different mass ratios of GO (1% and 3%) to asphalt. In addition, rheological properties were tested to investigate how GO could influence the asphalts by dynamic shearing rheometer tests. Finally, some interesting findings and potential utilization (warm mixing and flame retardants) of GO in asphalt pavement construction were explained.

Investigate of Performance of Asphalt Concrete with Gneiss

The use of gneiss as aggregates might help meet the pavement constructing demands. However, the study of the pavement performances of gneiss asphalt mixture is few. In this paper, the microstructure of gneiss aggregate was studied by Scanning Electron Microscopy (SEM). And the pavement performances of gneiss asphalt mixture with different improving measure were characterized by means of Indirect Tensile Strength Test and Four-Point Bending Fatigue Test. Gneiss is flaky, surface texture rougher and imporosity characteristic in microstructure, resulting to its adhesion and processing property are poor. Experiment results indicate that the use of hydrated lime replacing limestone power partly in filler can improve pavement properties of the gneiss asphalt mixtures distinctly.

Utilization of Gneiss in Asphalt Concrete Mixtures

Construction of the pavement has consumed a huge amount of high grade aggregates, such as basalt, limestone etc. In some region, these aggregates are very scarce and have to be produced and transported from far aggregate quarries which would cause the waste of energy and resources as well as the increase of cost. Large quantities of gneiss exist in China, the use of gneiss as aggregates might help meet the highway constructing demands and save. In this paper, the feasibility is analyzed with respect to different aspects. Physical properties of gneiss aggregate were evaluated using Los Angeles abrasion, specific gravity and flakiness index. Mixture properties were characterized in terms of Marshall stability, moisture susceptibility, soak wheel track and low temperature cracking resistance property. Experiment results indicate that the physical properties of gneiss aggregates can satisfy the related specifications and these gneiss materials as aggregates can be used in asphalt pavement. Results also show that the optimal gradation component of the mixture consists of the gneiss as coarse aggregate and the limestone as fine aggregate. The use of hydrated lime can improve the moisture susceptibility of the mixtures containing gneiss aggregates.

Function investigation of stone mastic asphalt (SMA) mixture partly containing basic oxygen furnace (BOF) slag

Aims In this paper, the effect of the size gradations of basic oxygen furnace (BOF) slag on the functional performances of stone mastic asphalt (SMA) mixture including skid and deformation resistances was investigated. Methods The industrially produced BOF slag coarse aggregates (BSCA) with size gradations of 4.75-9.5 mm and 9.5-16 mm were used. SMA mixtures were designed according to Marshall procedure. British pendulum number (BPN), indicating the skid resistance of asphalt mixture, was measured by a British pendulum skid resistance device. Flow number (FN) and Marshall quotient (MQ), reflecting the deformation resistance of asphalt mixture, were determined, respectively, based on the results of dynamic creep test and Marshall test (stability and flow value). Results Showed that BSCA with a size gradation of 9.5-16 mm performed better in improving the skid and deformation resistance of SMA mixture than BSCA with a size gradation of 4.75-9.5 mm. Furthermore, BSCA with combined size gradations, namely, 4.75-16 mm, worked the best. Conclusions These conclusions would benefit the future extensive utilization of BSCA in asphalt pavement.

Investigation of Rheological Characteristics of Carbon Fiber Modified Asphalt Binder

The performance of asphalt concrete is strongly dependent on the rheological properties of asphalt binders. In this paper, PAN carbon fiber was employed to improve the conductivity of asphalt mixture. To better understand the performance of conductive asphalt mixture, the present study investigated the rheological characteristics of asphalt binders containing PAN carbon fiber. Additionally, scanning electron microscopy (SEM) was used to elucidate the microstructure and interface reaction between the asphalt and the PAN carbon fiber. Experimental results showed that carbon fibers in the asphalt can overlap each other and form a three-dimensional space structure, which could transfer and buffer the stress. Moreover, the addition of PAN carbon fiber increases the complex shear modulus of modified asphalt binders, which means higher resistance to the permanent deformation. Furthermore, the reduction of phase angle implied the increment of elastic portion in the visco-elastic of carbon modified asphalt binder.

Self healing capacity of asphalt binders

To test self healing capability of asphalt binders, three asphalt specimens (pure asphalt, modified asphalt and aged asphalt) were prepared. Every specimen was tested by dynamic shear rheometer (DSR). The temperature sweeps result indicates that both aging and SBS modifying influence the self healing capability of asphalt binder. The fatigue-heal-fatigue test was introduced to study the self healing capability of asphalt in its serving periods. Furthermore, three different periods (0.5 h, 1 h, 3 h) were set up to study the influence of rest time on fatigue time. It is concluded that longer rest time, less load will delay the appearance of cracks and extend the service life of asphalt binders.

Study on Mechanical and Thermal Properties of Graphite Modified Cement Concrete

The comprehensive survey on the thermal conductive cement concrete consists of graphite is obtained in this paper. The effects of graphite on mechanical properties and thermal properties were investigated to determine the optimum materials design. Additionally, scanning electron microscopy (SEM) was used to elucidate micrographs of the fracture graphite modified cement concrete. Result indicated that graphite could greatly improve the thermal conductivity properties of cement concrete, but degrade the related compressive strength simultaneously. When the graphite content is 15%, the increment of the thermal conductivity was 50% while the reduction of the compressive strength was almost 90%. Furthermore, SEM images illustrated that the reason for the degradation of mechanical strength maybe depend on the flake structure of graphite.