The objective of this project is to test the hypothesis that roofing shingle scrap may be blended with asphalt binder through a wet process, in which the ground recycled material is blended with the binder at high temperature prior to mixing with the aggregates. Results of this research may revolutionize recycling practices of asphalt shingles in pavement construction by validating a new approach to incorporate discarded asphalt shingles into asphalt pavement construction. Current practices of dry blending Recycled Asphalt Shingles (RAS) with the aggregates before the asphalt binder is added to the batch are often criticized due to the large variability observed in the asphalt content of asphalt shingles. The proposed wet process may offer the potential to increase the percentage of asphalt shingles used in the mixture and may allow for a better control of the chemical and physical reactions taking place in the blend.
The proposed approach has the potential to cope with the increase in construction waste while reducing the consumption of petroleum products in asphalt construction and increase resource efficiency. Educational activities will seek to promote the understanding of sustainability concepts among undergraduate and high school students and to engage students from underrepresented groups into laboratory activities by offering two summer internships for a student from Southern University, a historically black institution, and for one female engineering student from LSU. Proposed educational activities will also establish a partnership between LSU, the flagship institution for the state, and Southern University and high schools predominantly serving underrepresented groups.
The Environmental Protection Agency (EPA) estimates that 170 million tons of construction and demolition (C&D) debris is generated every year with asphalt shingles making up to 15% of this waste. Recycling of asphalt shingles in asphalt paving mixtures is a promising approach for technical, economical, and environmental reasons. From an economic perspective, the use of RAS reduces the consumption of asphalt binder, a petroleum-based product, eases the disposal cost of shingle waste in landfills; and reduces energy consumption during processing and manufacturing of virgin materials. The disposal fee of waste shingles in landfills can reach $90 to $100 per ton in the neighborhoods of large cities and even up to $200 or higher in select California metropolitan areas. From an environmental perspective, the use of RAS reduces emissions of harmful by-products during processing and manufacturing of virgin materials, reduces consumption of virgin materials, and diminishes consternation of the public over emissions. The primary objective of this project was to conduct a laboratory evaluation of asphalt mixtures containing RAS prepared using a newly-developed process referred to as the wet process. The advantages of the proposed wet process are expected to be better control of the properties of binder blend, to stimulate chemical and physical interactions taking place in the blend between asphalt binder in shingles and virgin asphalt binder in the mix, and to reduce maintenance issues at the plant due to the high content of fines and fibers in RAS. Based on the results of the experimental program, it was determined that the use of RAS through the wet process allows the reduction of the virgin binder content with no adverse effects on the laboratory performance of the mixture as compared to the conventional mixture with no RAS. Results also indicated that the blending of RAS directly with its regular processed size at the recycling plant with no additional processing in the wet process is feasible with no foreseen adverse effects on the mixture performance. Educational activities conducted in this project significantly enhanced the understanding of the significance of sustainable materials in construction applications for high school and undergraduate students and engaged students from underrepresented groups into laboratory activities and related-research. Through funding from this project, the research team advised a student in a topic related to shingle recycling into roads. During his science project, the student came to the laboratory at LSU and witnessed the innovative process developed to recycle scrape roof shingle in asphalt pavements. The student took home first place in the recent Region VII Louisiana Science and Engineering Fair. He then participated in the state fair where he received 3rd place in Engineering – Material and Bioengineering category. He also received a special award for the Most Outstanding Exhibit in Material Science from the ASM Materials Education Foundation. As part of this program, 23 minority honor roll students in grades 6-8 from Community School for Apprenticeship Learning (CSAL) were introduced to the recycling of asphalt shingles into roads.
