Modeling the Effects on Energy and Carbon Dioxide from the Use of Recycled Asphalt Pavement in Hot Mix Asphalt

The transportation sector greatly influence the sustainable development of a society, contributing to pollution from vehicular emissions, global warming, consumption of energy resources, disturbance of natural space from infrastructure construction, and noise pollution. With an increased awareness of sustainable development, more recycled materials are being used for infrastructure construction. However, there is a lack of quantitative evaluation of how energy use and greenhouse gas emission are impacted by the use of recycled materials. Such an evaluation is critical for a comprehensive analysis of the effects of using recycled materials in pavement design. This study develops a mathematical model to quantify the impact of using recycled asphalt pavement in hot mix asphalt on energy consumption and greenhouse gas emission. The energy use and greenhouse gas emissions are affected by the RAP content in HMA, the moisture in the RAP, and the HMA discharge temperature. It was found that it takes more energy to dry/heat HMA with a low percentage of RAP than HMA with only virgin aggregate, while the opposite is true at high RAP percentage. After accounting for the amount of energy used in transporting and processing HMA, and the calorific energy of HMA, the use of RAP in HMA results in reduced energy consumption at all levels of RAP percentage, moisture content, and HMA discharge temperature. For low level of RAP content in HMA, the use of RAP in HMA increases CO2 emissions, while at high RAP content levels CO2 emissions decreases