Papers by Author: Jian Qiu

Abstract: Asphalt pavement serving as solar collector has been developed for the heating and cooling of adjacent buildings as well as to keep the pavement ice-free directly. Material parameters such as thermal conductivity and heat capacity are some of the critical parameters related to the efficiency of the asphalt collector. Graphite powders were utilized as thermal conductive fillers to make asphalt collector conductive so as to improve the efficiency of the asphalt collector. The material parameters change with the addition of graphite consequently. In order to access the solar energy absorbability of conductive asphalt collector, it is necessary to predict the temperature distribution within the asphalt layers. A transient, two-dimensional finite element model is developed to predict temperature distributions in conductive asphalt solar collector due to material parameters. The ability of accurately predict asphalt pavement temperature at different depths will greatly help pavement engineers in determining the solar energy potential of conductive asphalt collector. The results from the prediction model show that the surface temperature of pavement decreases slightly with addition of graphite. The differential maximum asphalt temperature variation at a depth of 10cm is significantly more than that at the surface. Higher temperature and lower temperature gradient can also be observed at the depth of 10cm because the heat conduction is accelerated by the addition of graphite.

Abstract: It is currently interesting to use thermal or electrical conductive asphalt concrete for snow-melting and maintenance of asphalt pavements in winter. The addition of conductive fillers may have negative effects on the mechanical properties of asphalt concrete. The performance of conductive asphalt concrete is greatly affected by the initial crack and its propagation. Laboratory tests for neat and conductive asphalt concrete include Dynamic Modulus Test (DMT) and Indirect Tensile Fatigue Test (ITFT). DMT tests indicates that the value of dynamic modulus of asphalt concrete decreases with the increasing graphite content. It means that the conductive asphalt concrete achieves lower stiffness. It can be concluded from ITFT tests that the fatigue life (load cycle times) of conductive asphalt concrete is more than neat ones when stress level is under 1.0 MPa. Meanwhile higher fatigue resistance of conductive asphalt concrete is observed when carbon fibers (2 weight % of total aggregate) were added together with 22% graphite, especially at low stress levels.

Abstract: Recycled asphalt mixture is a multiphase system, which consists of sized recycled asphalt pavement (RAP), new asphalt, and/or recycling agents and new aggregates. RAP percentages may have influences on performance of total recycled asphalt mixture. The performance of asphalt mixture is significantly affected by its dynamic response and fatigue performance (crack formation and propagation). Dynamic and fatigue properties of virgin and recycled asphalt mixture are investigated based on Indirect Tensile Test (ITT). It is demonstrated in test results that recycled asphalt mixture is stiffer and more elastic-like than virgin ones with RAP added. The number of load cycles to fatigue failure expected of recycled asphalt mixture is a bit decrease compared with that of virgin ones in low stress level. In addition, high fatigue resistance of recycled asphalt mixture is observed in this test when stress level is high.