The Modification Study On Lower-heat-storage Asphalt Mixture And The Assessment Of Its Impact On Heat Urban Environment

The Influence of Urban Effect on city human settlements has grasped more attention recently, and the high temperature damage of bituminous pavement will produce the adverse effect on city construction. Far infrared radiant material(FIRM) was used to instead of the limestone ore fines as the fill of asphalt mixture, and the infrared radiation asphalt mixture of which the heat storage is low was made by different proportion. By experiment, its cooling attribute and the road performance were studied, and the constitutive property was characterized by scanning electron microscope and the establishment of self-radiating model, and the influence of the infrared radiation asphalt mixture effect on urban heat island effect was analyzed with the model of atmosphere temperature field. In accordance with the result of mixed proportion design, the optimal asphalt content is linearly related to the FIRM content, the fomula on optimal asphalt content and FIRM content is given as flows: Y=5.926+21.35X/3, and the optimal asphalt content was increased by 0.2135%, as the FIRM content was raised by 3%.Infrared radiation experiment showed that the higher the FIRM content be, the lower the temperature of asphalt surface be. It can be lowered by 8.12℃at last. Compared with the asphalt of 0% FIRM content, all the the stability at high temperature and low temperature and the water stability of the the asphalt which was mixed with FIRM were improved to a certain degree . The Marshall stability of 6% FIRM content asphalt increased by 12.2% with the residual stability was up in 98.9%. The low temperature splitting tensile strength of 6% FIRM content asphalt increased by 21.3%. The friction coefficient of 6% and 12% FIRM content asphalt increased by 17.7% and 26.9% respectively. The experimental results of SEM confirm that the grain size of FIRM is finer and more uniform than the limestone ore fines. After the Impregnation of FIRM, the asphalt mastic become to be denser and more even-textured with the smaller holes and cracks.The self-radiating model of the pavement has been established, the model fomula is given as flows: 5.73×10^-8 ₁(T_e⁴-T_s⁴) = G_sa_s + h(T-T_e).It showed that if the radiant energy of the atmospheric window grows, or the long wave emissivity of the pavement raises, or the short-wave absorption rate of the sun goes down, even if the increase of the wind speed , the equilibrium temperature of the road surface will be lower. The atmosphere temperature field model of the Non-gray radiation shows that, the higher the atmospheric moisture is ,or the higher the equilibrium temperature of the pavement is, the higher the atmosphere temperature reached. The road used bituminous mixture of Low heat accumulation type, 1² meters up from the ground ,the air temperature reduced 3⁵℃.