Key Engineering Materials Vol. 599

Abstract: The diffusible rejuvenator containing dissolving-diffusing agent was prepared. Effects of the diffusible rejuvenator on properties of recycled asphalt mixture were investigated in comparison with those of common rejuvenator. The results show that the properties of recycled asphalt mixture were significantly improved with the addition of the diffusible rejuvenator due to its good diffusibility. Water stability, low-temperature cracking resistance and fatigue resistance of recycled asphalt mixture are closest to virgin mixture when increasing the diffusible rejuvenator content up to 15 wt%.

Abstract: An unravelling porous asphalt concrete was developed by adding steel wool and heating it with induction energy. The purpose of this paper is to examine the effects of the steel wool distribution on the properties of this unravelling porous asphalt concrete. The mixture was mixed for 10 min, 12 min, 15 min or 20 min respectively, and then samples were prepared with a gyratory compactor. The steel wool distribution at different mixing time was compared with CT scanning analysis. The electrical resistance, indirect tensile strength and induction heating speed of samples with different mixing time were also studied. It was found that a better distribution of steel wool in porous asphalt concrete increased its indirect tensile strength, but decreased its electrical conductivity and induction heating speed. 15 min mixing is sufficient to disperse steel wool to a homogenous distribution.

Abstract: In recent years, using rejuvenator sealer materials (RSMs) to recover the performance of aged asphalt on the pavement is becoming more and more popular. In this paper, four different RSMs were made and applied to rejuvenate the aged asphalt which experienced a PAV 20H process. Then the dynamic rheological characteristics of different binders were tested by the dynamic shear rheometer (DSR).The results indicated that the four RSM can recover the stress relaxation and fatigue factor of aged asphalt. But the rutting parameter decreased with the introduction of four RSMs.

Abstract: This paper analyzed the limitation of the stone mastic asphalt (SMA) mixture designing methods in China, then the Superpave Gyratory Compactor(SGC) method for SMA mixture where designing applicable and feasibility was analyzed, and SGC method was introduced to promote the application in SMA mixture design. It is found that the compaction work determined by the SGC design procedure was remarkably increased compared to that by Marshall design when the number of gyrations is 100. It is recommended that the number of gyrations should be decreased instead of 100 when SGC is used to design SMA mixture in China.

Abstract: Two bituminous binders were used in this research to investigate the influence of high-temperature volatilization on the binder performance. The results indicated that at higher temperature, the weight of bituminous binder reduced and the reducing rate was decreasing with heating time. After certain volatilization period, the softening points of bituminous binder increased while the penetration reduced significantly. The volatilization condition of oxygen and vacuum did not have significant differences on the asphaltene and colloid. The bitumen binder modified with 3% of Layered double hydroxides (LDHs) would reduce the amount of VOC fumes.

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 DSR was conducted to evaluate the influence of ultraviolet aging on asphalt rheological performance. In the experiment, RTFOT test was used to simulate the short-term aging of asphalt binder, indoor intelligent ultraviolet aging box is used to simulate ultraviolet aging of asphalt. The aging temperature was set at 50 ��C. Aging days were 2 days, 4 days, and 6 days. For high temperature frequency scanning and low temperature frequency scanning of ultraviolet aging asphalt. The experimental results show that the ultraviolet aging have great influence on asphalt basic performance indicators and rheological properties.

Abstract: Volatile organic compounds (VOC) emission from different asphalts not only causes the change in the performances of the bitumen, but also its chemical compositions. This paper carried out four-component analysis to study the influence of VOC emission from different asphalts on bitumens chemical compositions under different conditions. Results show that four-component of asphalts from different places is different. Also as the time of VOC emission increases, the total contents of resins and asphaltenes increase, but the total contents of saturates and aromatics decrease. VOC emission under different temperatures also has a great impact on the asphalt chemical components; Saturates and aromatics decrease in high temperature is larger than in low temperature, and there exists big differences in the asphalt surface layer and the internal of chemical components.

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: Layered double hydroxides (LDHs) were used to modify bitumen. Effect of LDHs on physical properties and chemical compositions of bitumen was investigated. Fourier transform infrared (FTIR) spectroscopy was carried out to analyze the structural change of LDHs modified bitumen after UV aging. The results show that LDHs is effective in improving the UV aging resistance of bitumen since the viscosity aging index (VAI) and softening point increment (SPI) of bitumen decrease while the retained penetration ratio (RPR) increases with increasing LDHs contents. The carbonyl and sulfoxide of LDHs modified bitumen presented a smaller increase after UV aging in comparison with unmodified bitumen according to FTIR analysis, and the changing rate of carbonyl and sulfoxide index of aromatics and asphaltenes reduced obviously compared with the slight changes of saturates and resins after the introduction of LDHs during UV aging, which demonstrated that LDHs mainly inhibit the oxidation of aromatics and asphaltenes during the UV aging.