As an industry, we have found ways to reduce our carbon footprint by increasing the use of reclaimed asphalt pavements (RAP). However, over the next 10 years, the industry will need to find ways to increase recycled content in our mix designs. This means reducing the amount of waste plastic and other materials that go into our mixtures. Also, the energy needed to dry and heat these mixtures will need to be significantly reduced.
Reclaimed Asphalt Pavement (RAP)
As roadways age, they need resurfacing or replacement to keep them functional and safe. Historically, the asphalt and aggregates on the old pavement are removed, hauled to landfills, and then reclaimed to be used in a new mix for roadway construction.
Reclaimed asphalt pavements (RAP) are the most commonly used recycled materials in the United States. A recent industry survey conducted by the National Asphalt Pavement Association in partnership with the Federal Highway Administration found that more than 100 million tons of RAP was collected and reused in 2018. Finished RAP material is processed to the desired gradation at a central facility and incorporated into hot mix or cold mix asphalt paving mixtures as an aggregate substitute. Reclaimed asphalt pavements are also stockpiled and sometimes used in granular base or subbase construction.
In addition to using more recycled content and reducing the use of fuel, many asphalt plant manufacturers are making efforts to increase energy efficiency. Solutions include storing aggregates internally rather than heating and drying them, which saves on both energy and CO2 emissions. Another solution is a lower temperature warm mix, which reduces odour and particulate emissions during production. It also offers improved fuel efficiency and a longer drum shell life, according to Terex.
Keeping your equipment and facility clean, safe, and in good working order can also go a long way toward increasing efficiency. An established maintenance plan can help you to avoid costly downtime and minimize your fuel costs. ENERGY STAR recently launched an Industrial Focus to connect asphalt producers to a broader network of energy saving practices and technologies. The focus is a collaboration between EPA’s ENERGY STAR program and the National Asphalt Pavement Association (NAPA). It will encourage asphalt mixture producers to reduce energy consumption and costs at the plant level through proven energy-saving technologies and practices.
In response to the Oil Embargo of the 1970s, the asphalt industry has embraced recycling. Recycled materials are screened and recombined as needed to have the optimum gradation and mix properties. Recycled asphalt is typically a combination of crusher and pit run aggregates and is used in place or as the base course for new pavement. It may be mixed with virgin materials to produce an HMA.
The amount of RAP material and the rejuvenating agent used in the mix design are critical to achieving the best performance possible. Because of this, it is important that research be done to help determine the best RAP and rejuvenating agent combinations for each specific application. Several tests have been performed to evaluate the performance of asphalt mixtures with varying RAP content. Results show that RAP content has a significant effect on the dynamic modulus and mechanical strength of recycled asphalt mixes.
The asphalt industry and asphalt plant manufacturers must adapt to numerous environmental regulations. These regulations affect every aspect of asphalt production and can be challenging for producers to understand. For example, the EPA Area Source Rule for asphalt processing and roofing products manufacturing has been in effect since December 2, 2009. This rule specifically covers only facilities that produce polycyclic aromatic hydrocarbons, which is considered a hazardous air pollutant (HAP).
Another issue to consider is material waste and by-products. For example, the use of high temperature metal recovery slags in pavement applications requires testing for their environmental properties. In addition to this, recycling is a huge opportunity for the asphalt industry. In fact, it’s already happening in massive amounts.