The asphalt industry is America’s number one recycler. Asphalt pavements enhance public safety and they reduce noise. Furthermore, greenhouse emissions are lower during the production and construction of asphalt pavements, and greenhouse emissions produced by the traveling public are reduced through the use of asphalt pavements due to the speed that these pavements can be constructed. All of these factors help to make asphalt the environmental pavement of choice. Asphalt pavements possess Environmental, Engineering, and Economical benefits which are second to none in the pavement industry. These three “E’s” help make asphalt the preferred pavement type in America. From an environmental perspective Asphalt is the sustainable material for constructing pavements. Asphalt roads don’t wear out, and they are the only pavement type that can be a Perpetual Pavement. Energy consumption by producers, contractors and the traveling public is less when building and using asphalt pavements.
The high population growth rate being experienced in Texas has put a premium on the use of Texas’ natural resources. The citizens of Texas are also becoming more environmentally conscientious. With this in mind the asphalt paving industry has continued to work to make the production of asphalt materials and the placement of these same materials the most environmentally friendly product in the highway heavy paving industry. The asphalt paving industry through TXAPA’s partnership with the Texas Department of Transportation (TxDOT) has stepped up to meet these environmental concerns by adding tools to a product that is already the most environmentally friendly paving product available to owners. Specifications have been developed or are under development that allow the addition of recycled asphalt pavement (RAP), recycled asphalt shingles (RAS), and warm mix asphalt (WMA) additives to asphalt mixes. All of these additions, along with other changes in TxDOT specifications, have helped to continue to make asphalt the environmental product of choice on Texas roadway projects.
The use of RAP helps to reduce the quantity of virgin binder and aggregate in asphalt pavement, and it helps to reduce carbon dioxide equivalent (CO2eq) quantities. Asphalt pavement is America’s most recycled product. Across the country the asphalt industry reclaims approximately 100 million tons of its own product every year and it reuses or recycles about 95 million tons. Furthermore, the inclusion of 20% RAP in asphalt pavements can reduce CO2eq by approximately 8.5%.
The use of RAS helps to reduce waste bound for America’s landfills and it reduces CO2eq levels. 11 million tons of waste asphalt roofing shingles are produced in the United States every year. Asphalt shingles are comprised of various fibers and fine aggregates, and 24% of the material making up asphalt shingles is asphalt. To bury this material in landfills across America would be tragic waste when it can be used very successfully in asphalt pavements. Asphalt pavement is the most common process to which shingles can be added and the best use of shingles. The use of 5% RAS in asphalt pavement can reduce CO2eq by approximately 7%.
The use of WMA can reduce carbon emissions, improve in-place densities, produce more durable pavements, improve ride quality, facilitate the use of RAP and RAS, provide a better work environment for workers, provide a wider paving window, and provide a direct energy savings. WMA is defined as additives or processes that allow a reduction in the temperature at which asphalt mixtures are produced and placed. Under current TxDOT specifications the required temperatures for WMA to be considered warm mix is between 215-275 degrees Fahrenheit and the use of WMA additives as a compaction aid is 215-350 degrees Fahrenheit. WMA can be combined with RAP and/or RAS. The use of WMA in asphalt pavements can reduce CO2eq by approximately 10%. Combining the use of RAP, RAS and WMA can lead to CO2eq reductions of nearly 25%.
For a more in depth discussion of CO2eq and possible reductions through the use of RAP, RAS and WMA please read “Paving the Way for the future of Texas.”
To read more on the environmental benefits of using asphalt please read the following pamphlets produced by the Asphalt Pavement Alliance (APA) and see the APA’s Environment section.