Research On The Performance Durability And Long-term Efficiency Of Asphalt Pavement For Solar Energy Collecting

Collecting solar energy from asphalt pavement is recognized as a positive method for sustainable development of road engineering, utilization and application of renewable energy source, mitigation of urban heat island effect. Many efforts have been made on the involved issues of the novel functional pavement. Previous studies mainly focused on the parameters that affect the energy collecting performance and methods that improve the energy collecting efficiency. However, few literatures investigated the durability of asphalt solar collector and its long-term performance of heat collection, which may limit the popularization and application of this promising technology.The main objective of this thesis is to investigate the durability of asphalt solar collector and its long-term performance of heat collection. The durability of asphalt binders and asphalt concrete was evaluated by indoor ageing test and water temperature coupling tests; in view of the contact interface of heat transfer pipe and asphalt concrete, the bonding strength of pipe and concrete was studied by central pulling test, the effects of pipe on the pavement performance of asphalt concrete were investigated by the rutting test, three-point bending test, compression creep test and four-point bending fatigue test; in consideration of raw materials and service conditions, the effect of materials(asphalt, aggregate and filler) and conditions(temperature, moisture, ageing and water temperature coupling) on the thermal characteristics of asphalt binders and asphalt concrete were studies by thermal constants analyzer TPS 2500s; a heat collecting model of asphalt solar collector was established and used to analyze the characteristics of heat collecting performance of asphalt pavement. Based on the research results, the following conclusions can be drawn:(1) To improve the performance of asphalt solar collector, graphite was employed to prepare thermal conductive asphalt concrete. Results indicated that graphite can improve the anti-ageing performance of asphalt concrete, but weaken the resistance to water temperature coupling effect. The negative effect of graphite could be mitigated by controlling the air void of asphalt concrete. It is recommended that the design air void of thermal conductive asphalt concrete using for solar collector may not excess 4.0%. The mass content of graphite substituting for mineral filler should be below 30%.(2) The bonding strength between the heat transfer pipe and asphalt concrete has a relationship with the bonding length of pipe-concrete. The bonding strength decreases with the freezing-thaw process prolongs. Utilization of bonding materials(like modified emulsified asphalt or epoxy asphalt) can significantly improve the bonding strength between the pipe and concrete.(3) Compared to traditional asphalt concrete, the dynamic stability and fatigue life of asphalt concrete with pipes decreased by 26.4% and 50.8% respectively, while the stiffness modulus increased by 58.5% under the same experimental conditions. It indicated that the pipes would weaken the pavement performance of asphalt concrete. In consideration of the cooling effect in summer and the heating effect in winter, the asphalt concrete with pipes shows better higher resistance to rutting and cracking than that of concrete without pipes. The reason may be that the heating and cooling effect makes the asphalt pavement with pipe service in better conditions. Moreover, enhancing the bonding properties of pipe and concrete could effectively improve the fatigue property of asphalt concrete.(4) Thermal properties of asphalt concrete highly depended on the thermal characteristics and volume fraction of raw materials. The aggregate and fillers with high conductivity has a significant effect on the thermal properties of asphalt concrete. When the material compositions and preparation methods are certain, the temperature, moisture, asphalt ageing and water-temperature coupling have a pronounced effect on the thermal properties of asphalt concrete, especially water temperature coupling effect. The change of thermal properties of asphalt concrete is a important parameter to analyze the heat collecting efficiency of asphalt pavement during service period.(5) In consideration of the effect of service conditions on the thermal properties of asphalt pavement materials, the solar collecting performance of new pavement and old pavement(after 30 freeze-thawing cycles) is compared under the same conditions. The results indicated that the heat collecting performance of old pavement was slightly better than that of new pavement. When the length of embedded pipe is 63.2m, the outlet temperature of old pavement is increased by 1oC and the heat collecting efficiency is increased by 2%. Anyway, the little difference indicated that the asphalt pavement has a stable heat collecting performance.