Papers by Author: Ling Pang

Abstract: Servicing in the natural environment, asphalt pavement is often exposed to the various aqueous solution, however, the effect of different media aqueous solution on road performance of asphalt mixtures remains ambiguous. In this study, the influences of water, acid, alkali and salt solution on volume of air voids (VV), tensile strength rate (TSR), low temperature performance of 70^# asphalt mixtures and SBS modified asphalt mixtures were investigated through freeze-thaw cycles test, void ratio test, Lottman test and Three-point Bending Fracture (TBF) test. The results indicated that freeze–thaw cycles influenced the road performance of asphalt mixtures significantly, increased the air void of asphalt mixtures, and reduced tensile strength ratio and failure strain of asphalt mixtures. Compared with the distilled water, the damage of acid, alkali and salt solution on the road performances of asphalt mixtures were more serious, especially alkali solution to tensile strength rate and failure strains in low temperature, and salt solution to VV. The moisture corrosion resistance of SBS modified asphalt mixtures is better than that of 70^# asphalt mixtures.

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: Three types of rejuvenator sealer materials were added into asphalt mortar after thin-film oven test (TFOT) and pressure aging vessel (PAV) aging processes. The performances of both aged mortar and rejuvenator treated mortar were evaluated by means of softening point, temperature sweep tests. Experimental results showed that all of rejuvenator sealer materials can significantly increase phase angle and decrease the softening point and complex modulus of TFOT aged asphalt, which means aged asphalt can be efficiently softened with the rejuvenator materials. However, the influence on PAV aged asphalt was slightly in the same concentration, which has a significantly direction for the pavement preservation.

Abstract: 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.

Abstract: 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.

Abstract: Rejuvenating seal, widely used due to its economic benefits and convenience, is one of the preventive maintenance methods. The rejuvenating seal materials (RSM) work on the surface course of asphalt pavement. This paper described the effects of RSM on the physical properties and rheological properties of aged SBS modified asphalt (ASMA). Two RSM, R and C, were involved in this research. The dosage of each RSM was 2%, 4%, 6%, 8%, and 10% of ASMA by weight. Physical properties, including softening point, penetration and ductility, were tested. Rheological properties were carried out by means of dynamic shear rheometer (DSR). Results show that RSMs, R and C, have improved the low-temperature performance and fatigue resistance. R has more positive effect on low-temperature performance and fatigue resistance of ASMA compared to values of C.

Abstract: Light components in the asphalt can volatilize under the circumstances of high temperature or long-term service process, leading to the deteriorating of the asphalt pavement. This paper tried to discuss the influences of volatile organic compounds (VOC) emission from the asphalt on physical properties in the high temperature (at 180) by grey system theory. Both Heat and Vacuum environment were monitored as the emission conditions and the emission temperature was 180°C, physical properties of asphalt, released and unreleased were analyzed. Basic tests, including mass change, chemical compositions, penetration and soften point, were used to compare the influences of VOC emission on the asphalts performances. Meanwhile, grey system theory was used to investigate the sequent performances influenced by VOC emission. Results show that physical properties and four generic components of the asphalts are affected obviously in these two emission conditions, and the oxygen may promote VOC emission from the asphalt. In additional, the greatest factor associating with VOC emission is light components in the asphalt.

Abstract: The fitting models of dynamic modulus of asphalt mixtures were studied in this paper. UTM dynamic modulus tests were adopted to determine the dynamic modulus of two asphalt (A, B) mixtures. Then, the WLF equation and Arrhenius formula, based on the time-temperature equivalence principle, were used to get the shift factors and master curves of asphalt mixtures. Combined with Sigmoidal model and CAM model, it was founded that the Arrhenius formula was more suitable to get the master curves of asphalt mixtures. What is more, the CAM model was more suitable to fit master curves of both asphalt mixtures.

Abstract: Montmorillonite (MMT), a typical layered silicate, has been widely used to prepare modified asphalt. This paper investigates the high temperature performance and low temperature property on layered silicate modified asphalt concrete. The control concrete is prepared by base asphalt. Meanwhile, three-point bending, conventional and SHRP rutting tests are used to compare the properties of the two types of asphalt concrete. The results of conventional and SHRP rutting tests show that the modified asphalt concrete exhibits a better high temperature performance than the control concrete. And the maximum bending strength of modified asphalt concrete is higher than that of control concrete at the same temperature. It can be concluded that both the high temperature performance and low temperature property of asphalt concrete has been improved efficiently by utilization of layered silicate modified asphalt.

Abstract: Ultraviolet(UV) radiation is one of the main factors induce asphalt aged in the field in-service. Asphalt mortar greatly affects the pavement performance. It is scarce that studies concerning UV aging on the performance of asphalt mortar. In this paper, asphalt mortar with a 1.0 F/A (filler to asphalt)after UV aging were subjected to the test of the Dynamic Shear Rheometer (DSR).Effects of UV aging on the High-Temperature and fatigue performances of asphalt mortar were studied by using the rutting parameter G*/sinδ, fatigue parameter G*sinδ and dynamic viscosity. The results show UV aging had prominent effect on asphalt mortar’s properties, with the decrease of film thickness and increase of UV aging temperature, the ability of rut resistance enhances and fatigue performance weakens.