Study on Reducing Dioxide Carbon Emissions of Rubber from Modified Asphalt Materials

Abstract

The construction of new asphalt pavements has resulted in the release of greenhouse gases into the atmosphere. However, recent advancements have introduced products like Sasobit®, which can lower asphalt viscosity at lower temperatures compared to conventional mixtures. This temperature reduction has the potential to effectively reduce greenhouse gas emissions. The objective of this study was to evaluate the emissions reduction potential of warm mix asphalt (WMA) compared to hot mix asphalt (HMA) produced at higher temperatures, as well as to assess any improvements in material properties. Additionally, the study aimed to determine the economic benefits associated with producing mixtures at lower temperatures. To conduct the study, emissions testing was performed on pure asphalt and asphalt mixes. Samples of HMA and WMA were mixed and compacted to evaluate material properties. Three different mixes were tested: HMA with 7.3% asphalt, WMA with 7.3% asphalt and 1% Sasobit® (by mass of asphalt), and WMA with 6.8% asphalt and 1% Sasobit® (by mass of asphalt). Emission tests were carried out using Drager test equipment, including flasks, ovens, a Drager pump, and Drager tubes. The Drager pump required 10 full strokes to measure carbon dioxide (CO2), and the concentration of CO2 in parts per million (ppm) was indicated by the color change in the tube. Preliminary testing was conducted on emissions from pure asphalt to establish a testing procedure since no existing standards were available. The emissions testing involved approximately sixty grams of WMA and HMA asphalt mixtures, as well as approximately twenty-five grams of pure asphalt. The three asphalt mixtures were subjected to tests under controlled conditions and aged to evaluate their material properties according to standards set by the American Society for Testing and Materials. The tests included analysis of bulk specific gravity, theoretical maximum density, and indirect tensile strength to determine volumetric and mechanical properties. The volumetric properties assessed were the percentage of air voids, adsorption, and effective asphalt content. After comprehensive testing and analysis of the three asphalt mixes, it was concluded that the addition of Sasobit® as an additive in WMA yielded positive results. The changes in material properties led to stronger and more durable asphalt mixes, as well as an extended paving season. By incorporating Sasobit®, the production temperature of HMA could be lowered by 20°C, potentially resulting in a reduction of up to 43.9% in annual carbon dioxide emissions from the asphalt industry. This reduction VI encompasses emissions from both fuel usage and the asphalt materials used in hot mix asphalt production. Furthermore, the lower temperature requirement for Sasobit® asphalt mixes could generate energy cost savings exceeding $69 million. The environmental impact of utilizing Sasobit® asphalt mixes in the industry is significant. By reducing greenhouse gas emissions from asphalt mixing materials and production energy, it has the potential to contribute to the improvement of the Earth's atmosphere. The study estimated that annually, the use of Sasobit® could prevent 3.774 million tons of carbon dioxide emissions from asphalt mixing materials and production energy. Over a span of ten years, this would amount to preventing 37.74 million metric tons of carbon dioxide emissions. It is crucial for the asphalt industry to prioritize its environmental impact, and the incorporation of Sasobit® into asphalt mixes represents a promising step in that direction