Effects of Physical Cooling on the Temperature and Performance of Newly Laid Porous Asphalt Mixtures

Abstract

Porous asphalt pavements need to be cured for 24 h~48 h before they can be opened to traffic. In an emergency, physical cooling methods, such as water sprinkling and air blowing, can be used to accelerate cooling, but the effects of the two methods on the mechanical properties and durability of porous asphalt mixtures are still unclear. In this research, firstly, the dropping and rising temperatures of the pavement surface during the water sprinkling process of newly laid porous asphalt mixtures in real projects were analyzed. The effects of the two conditions of water immersion and water sprinkling on the mechanical properties of porous asphalt mixtures were clarified, and water sprinkling technology for porous asphalt mixtures was proposed. Secondly, the effects of air blowing on the temperature reduction and strength loss of porous asphalt mixtures was analyzed, and the pavement surface temperature control standard that was suitable for air blowing was proposed. Finally, a seven-year observation was carried out on the water sprinkling cooling test section in the actual project. The research results show that water immersion or the sprinkling of water repeatedly during the curing period of porous asphalt pavements reduces the strength of the mixture. It is recommended to use a water amount of 0.3 kg/m2 once and sprinkling four times before painting road markings and two times after painting road markings; this was the best water sprinkling cooling process for porous asphalt pavements. The use of air blowing can accelerate the temperature reduction of porous asphalt mixtures, but the mechanical properties of the mixtures are attenuated after air blowing. Air blowing can be carried out when the pavement surface temperature is lower than 70 °C. Compared with the road section without water sprinkling for cooling, the use of the determined process to cool the newly laid porous asphalt mixtures by water sprinkling does not have a significant adverse effect on their durability. There is also no significant difference in the performances of the two road surfaces within a seven-year service. In an emergency, physical cooling methods, such as water sprinkling or air blowing, can be used to accelerate the temperature reduction of the newly laid porous asphalt mixtures, so as to achieve the purpose of quickly opening to traffic.