Research Project Summary Information
Low-Energy Asphalt Development(ST10381-1)
For many years, the road construction industry has been seeking ways to reduce the amount of energy required to manufacture hot mix asphalt (HMA) in order to combine energy savings and environmental benefits. One approach to achieving these goals would involve methods to reduce material production temperatures. The concept of warm-mix asphalt (WMA) has been introduced over the last few years as a means to these ends. Despite their validity, these mixes have not yet been able to gain ground in relation to HMA because the cost of warm mix exceeds that of HMA, making WMA an unviable alternative unless its use is mandated.
Current and impending regulations regarding emissions are making it more attractive to consider reductions in HMA production temperature. While stack emissions have decreased significantly over the past 35 years due to improved pollution controls, further reductions in the emission of greenhouse gases will likely be required in the future. In addition, current state and local regulations are such that in some ozone non-attainment areas, HMA plants are sometimes required to curtail operations in daylight hours during certain times of the year when ozone formation is problematic. Newly adopted ozone standards will create additional ozone non-attainment areas, along with new, more stringent demands for emission reductions in the future, and the demonstration that transportation plans and projects are in conformity with the Clean Air Act.
A new warm-mix technology is emerging in France called Low Energy Asphalt (LEA). This new process relies on sequential mixing of the asphalt binder with a chemical additive being added to the hot coarse aggregates, followed by the introduction of wet sand that creates a foaming action. The wet sand fraction, which could be as high as 40% of the total mixture, is unheated in this process. Since the sand (or fines) carries the most moisture, it subsequently requires the most amount of energy to dry. With a desired mix discharge temperature of around 200 degrees Fahrenheit coupled with the unheated sand fraction, the LEA Process provides the greatest reduction in energy consumption of all the available warm-mix processes. Preliminary laboratory work indicated that with the use of some of the European chemistry the LEA mixture exhibited performance equal to its HMA equivalent.
Currently, in New York State approximately 20,000,000 tons of HMA is placed annually. It typically takes about 3 gallons of fuel oil (if used) to heat each ton of HMA. If all HMA in NY were switched to LEA, the potential reduction in fuel oil consumption would be around 30,000,000 gallons annually. Substantial reduction in energy consumption during the production of asphalt roadway paving materials – LEA reduces the consumption by 40 – 55% compared to conventional HMA. Potential reduction of fuel could be as high as 30 million gallons of fuel oil annually in New York alone. Reduced fuel consumption results in reduced emissions – allowing better compliance with current and impending New York State and federal regulations – preserving our industry jobs. Based on the energy reductions estimated above, greenhouse gas emissions would also be reduced by almost 50%.
1911 Lorings Crossing Rd
Cortland, NY 13045
NYSERDA Contact Information
R&D -Transport & Power Systems