Zongwu Chen

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.

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.

Low temperature properties of UV aged asphalts containing layered double hydroxides modifier

Background In recent years, ultraviolet (UV) ageing of asphalt has attracted worldwide attention from researchers in the asphalt field. The UV radiation can result in the ageing of asphalt and thus influence its performance. So far, a variety of UV blocking materials have been investigated. Aim In this paper, layered double hydroxides (LDHs) were introduced as the UV blocking materials into three different asphalts (S70, S90 and SBS modified asphalt). Methods The low temperature properties, such as equivalent breaking point (EBP) and fatigue factor were tested and applied to estimate the UV blocking effects of LDHs on asphalts. Results The experimental results demonstrated that LDHs could effectively reduce the ageing index of S70 and S90, and lower the degradation rate of SBS modifier.

Residual Fatigue Properties of Asphalt Pavement after Long-Term Field Service

Asphalt pavement is widely used for expressways due to its advantages of flexibility, low cost, and easy maintenance. However, pavement failures, including cracking, raveling, and potholes, will appear after long-term service. This research evaluated the residual fatigue properties of asphalt pavement after long-term field service. Fatigue behavior of specimens with different pavement failure types, traffic load, service time, and layers were collected and characterized. Results indicate that after long-term field service, surface layer has a longer fatigue life under small stress levels, but shorter fatigue life under large stress levels. Longer service time results in greater sensitivity to loading stress, while heavier traffic results in shorter fatigue life. Surface and underneath layers present very close fatigue trend lines in some areas, indicating that the fatigue behavior of asphalt mixture in surface and underneath layers are aged to the same extent after eight to ten years of field service.

Function evaluation of asphalt mixture with industrially produced BOF slag aggregate.

Background Laboratory research suggested that basic oxygen furnace (BOF) slag-based asphalt mixture was a functional material. However, the BOF slag aggregates quality was difficult to control when it was heavily used in entity engineering. Aims The primary objective of this research was to evaluate the functional performances of asphalt mixture containing BOF slag coarse aggregate (BSCA), which was from an industrialized production line. Methods Limestone mixture was a control group. The Marshall method was first adopted to design asphalt mixtures. The performances of limestone asphalt mixture and BOF slag asphalt mixture including fatigue failure resistance and moisture stability were then evaluated and compared. Results Results showed that the asphalt mixture containing BSCA possessed better durability, which meant the quality of BSCA from industrialized production lines was well controlled and this BSCA can be heavily used in entity engineering.