Research On Heat Reflectionand Thermalresisitance Technology Of Asphlat Pavement Cooling Mechanism And Its Application

Asphalt pavement is widely used in our country because of driving comfort and performance. Hot mixture asphalt is sensitive to temperature. High temperature decreases modulus of HMA. With the effect of vehicle load time and again, permanent deformation such as rut, folding and slippage occur. These would decrease driving safety and shorten road work life. Traditional measures solve these diseases by using high quality asphalt and aggregate or choosing skeleton dense structure for HMA. All these increase road engineering cost and construction difficulty. The over high road temperature is accepted passively. Even all these measures are taken, high temperature diseases are not solved completely. Main reason leading this is over high temperature of road structure. By reasonable materials selection and structure design, the temperature of road can be decreased by using heat reflection and thermal resistance technology and reduce high temperature diseases at a certain extent without increasing road cost. At the same time, with the process of urbanization in our country, the Urban Heat Island effect becomes a more and more serious environment problem. The UHI effect harm citizen health and increase power demand for cooling in summer. Application heat reflection and thermal resistance technology in city pavement can mitigate UHI effect.In this paper, factors effecting road structure temperature field are analyzed. The decreasing temperature mechanism and feasibility of heat reflection and thermal resistance technology are researched. The heat reflection coatings are developed. Decreasing temperature effect and road performance are tested. Thermal resistance wearing course are developed. The materials compose is determined by considering thermal resistance and road performance. The optimum void range for porous asphalt mixture is suggested by researching thermal resistance effect and mechanics performance. Construction technology of heat reflection coating is provided by construction and observation of experimental road. All research works in the paper are outlined as following:Decreasing temperature mechanism and feasibility of heat reflection and thermal resistance is analyzed. Based on heat transfer theory and asphalt pavement light-heat environment, a temperature field computing model of asphalt pavement is built by ABAQUS finite element software. The model is verified by field test results. According to analysis of single factors influence on temperature field, increasing reflectivity and emissivity can decrease temperature at anytime. Increasing specific heat can decrease temperature at high temperature time. Decreasing thermal conductivity can increase surface temperature slightly but decrease temperature under middle layer largely. Sensitive analysis about thermal properties on temperature field is carried out. Those results can direct materials choosing and structure design. Then five materials with typical on thermal properties are chosen to research the thermal properties influence on temperature field. The results provide theory base of using heat reflection and thermal resistance technology to decrease rut and mitigate UHI effect. The feasibility of heat reflection and thermal resistance technology is discussed by researching construction materials thermal properties.Indoor simulation solar radiation system and asphalt concrete thermal properties experiment are developed. Based on radiation energy equal principle, the radiation time and intense is determined. Decreasing temperature effect can be evaluated quantitatively. Precision and stability of the developed system are tested by field results. Test method of asphalt concrete thermal properties is designed based on plane-source method with constant heating rate. Thermal resistance effect is evaluated by thermal properties.Heat reflection coatings for road are developed based on heat reflection technology. Film-formers, complex and pigments are determined to conform heat reflection coating by researching decreasing temperature mechanism, reflectivity, glare effect, work life and cost. The materials are water-soluble, low cost, easy construction, no pollution and short curing period. The best heat reflection coating is determined by considering decreasing temperature and road performance.Thermal resistance wearing course materials are developed based on thermal resistance technology. Sintered clay and crushed ceramic with smaller thermal conductivity are taken as partial aggregate to form thermal resistance wearing course materials. Test the thermal properties, decreasing temperature effect and road performance. The reasonable dosages of sintered clay and crushed ceramic are determined by considering thermal resistance effect and road performance. The reasonable void range of porous asphalt mixture is discussed by researching different void decreasing temperature effect and road performance.Key construction technology of heat reflection coating is researched. Heat reflection sprayer with high automatic is developed for fast and effective construction. Decreasing temperature effect, road performance and work life are researched through experimental road.