Modification of AC Thermal Properties to Mitigate UHI Effects

An analysis of the asphalt concrete (AC) pavement material properties that affect surface temperatures is presented. These properties affect the contribution to the urban heat island effects. Its goal is to analyze the effect of various alternative aggregate materials, such as limestone, silica, polymer, glass, and graphite, on AC pavement surface temperatures under various environmental conditions. Pavement surface temperatures were analyzed for two extreme weather locations in the United States, namely South Texas and Northern Minnesota. Long-Term Pavement Performance weather data over a year-long period were analyzed for each location using the computer model Temperature Estimate Model for Pavement Structures. The average and range of pavement temperatures were compared at a depth of 0.01 m. It was concluded that the higher the coefficient of thermal conductivity, heat capacity, and albedo of the pavement surface layer, the lower the average and maximum surface temperatures are during the summer months. Graphite was shown as a promising limestone aggregate substitute producing significant reductions in AC surface temperatures. It reduced the peak daily surface temperatures by between 3.5°C and 5°C. On the other hand, the modified AC mixtures showed mechanical properties not quite at par with those of conventional ACs.