 with an average of 50°F temperature reduction. The lab testing results indicate that the WMA mix will perform similar or even better than the HMA control mix in terms of air voids, stability and moisture damage sensitivity.
The added cost of the Sasobit material was almost fully compensated by the fuel saving (up to 37% with 50°F temperature reduction) due to the lower mixing temperature. The benefit of low emission and less odor, better pavement durability due to less aging, and the potential to promote low temperature or night paving capability are just extras.
Emission is one of the biggest issues with the rubberized asphalt mix. The production rate is limited to approximately 1000 tons per day because of the restriction for maximum allowed emission. The WMA technology appears to be able to significantly reduce the emission of asphalt plant therefore allows a significant improvement in the plant production rate for rubberized asphalt mix.
A message from NCAPA asphalt bulletin6 indicates that HMA industry needs to be cognizant of the current environmental regulations that HMA industry will face in the coming years. Several limits including NOx and CO2 limits have been developed and implemented. This is evident in Environmental Protection Agency (EPA)’s implementation of the National Ambient Air Quality Standard (NAAQS) and the recent adoption of the San Joaquin Valley Air Pollution Control District (SJVAPCD) Rule 4309. International Agency for Research on Cancer (IARC) will conduct a major study of asphalt fume research and make a determination as to whether asphalt fume is carcinogenic. All these major efforts will have significant effects on how the industry produces HMA.
How we address these challenges will determine the future of HMA as a viable and environmentally friendly road building material. With all the benefits on energy consumption saving and a commensurate reduction in CO2 emissions and a reported up to 90% reduction in fumes7, the WMA technologies appear promising though there is still a lot to learn about this new technology.
- U. S. Department of Transportation, Federal Highway Administration. “Warm Mix Asphalt Technologies and Research”, www.fhwa.dot.gov/pavement/asphalt/wma.cfm, accessed July 2005.
- Damm, K-W, J. Abraham, T. Butz, G. Hildebrand, and G. Riebeschl. “Asphalt Flow Improvers as ‘Intelligent Fillers’ for Hot Asphalts—A New Chapter in Asphalt Technology.” In Journal of Applied Asphalt Binder Technology, April 2002, Pp 36–69.
- Butz, T., I. Rahimian, and G. Hildebrand. “Modifications of Road Bitumens with The Fischer-Tropsch Paraffin Sasobit®.” In Journal of Applied Asphalt Binder Technology, October 2001, Pp 70–86.
- Hurley, G.C., and B.D. Prowell. “Evaluation of Sasobit® for Use in Warm Mix Asphalt” NCAT Report 05–06, Auburn, AL 2005.
- Brits, C.H. “Sasobit Inverstigation” Report No. 100035/S9/2004/11/05/CHB/av/1, Geostrada Engineering Materials Laboratory, South Africa, 2004.
- NCAPA, “Northern California Asphalt Pavement Association’s Asphalt Bulletin”, Volume 10, Issue 1, Feb, 2006.
- Newcomb, D., “Warm Mix: the Wave of the Future”, HMAT, July, 2005.