Sustainable Land Development Today - June 2008 - (Page 14)

Asphalt from Corn Stalks? Researchers at Iowa State University at Ames, Iowa have produced promising results for an additive to asphalt cement (AC) that is derived from biomass, such as corn stalks and switch grass as well as ethanol and forestry byproducts. The study is focused on utilizing a substance called lignin to enhance AC performance while reducing the overall amount of the binder, which is rising in cost like other petroleum-based products. Heated to 500C in an oxygen-free container, the renewable material yields bio-oil which can be further reduced to other substances. The heaviest of these is tar like and contains the lignin, which is an anti-oxidant. Asphalt pavement is adversely affected by oxygen in the atmosphere, which causes the petroleum-based binder to stiffen and eventually crack. The anti-oxidant properties of the lignin retard that process. The lignin also widens the temperature range of the binder and shows positive interactions with polymers, according to Dr. Christopher Williams of the ISU Department of Civil, Construction, and Environmental Engineering, and lead researcher on the project. The study looked at blends that replaced up to ninepercent of the AC. “We think we can go much higher than that and in fact we think it is very possible to replace the asphalt component and thus have a 100 percent bio binder,” Williams said. The study is a joint project of the Center for Sustainable Environmental Technologies and the Center for Transportation Research and Education at ISU and is sponsored by the Iowa Energy Center. An associated research paper can be found at: www.ctre.iastate.edu/pubs/midcon2007/McCreadyLignin.pdf Hansen said that such unfunded mandates need to go by the wayside. “It actually hurt the asphalt rubber industry for a time,” he said. “You have to find out what are the properties you want from the material, and let the market place decide if it’s going to be costeffective.” Cost versus performance Hansen contends that rubberized asphalt is sold more on performance than on reduced costs. When used in the gapgraded and open-graded mixes, more of the base AC has to be used. But the end result can be a more durable pavement. “It always increases the cost. If 20 percent (of the AC) is made up of crumb rubber, the remainder is the asphalt binder. So you’re increasing that quite a bit over what would be the normal mix,” he said. “The idea is to get the performance, primarily by modifying the binder, which improves its high-temperature performance, and put in more of the binder to improve durability.” However, Carlson points out that the blends that use a rubber particle have cost-saving potential. EVERY ROAD IS PAVED WITH GOOD INTENTIONS.> Only Roads Built with Tensar ® BX Geogrids Follow Through. It looks good today, but how will it perform tomorrow? When you specify Tensar® Biaxial (BX) Geogrids, everyday performs as well as the ﬁrst. BX Geogrids interlock with ﬁll over weak soils and foundations to create composite formations that distribute loads, resist lateral spread and provide stronger support. So instead of getting that sinking feeling, you get a better road surface, increased pavement life and reduced maintenance. All with simpliﬁed construction and lower installation costs. Why settle for a solution that goes only halfway? Insist on Tensar BX Geogrids. Call 866-504-7950 or visit www.tensarcorp.com/s2 for your free copy of SpectraPave3TM Software today. ©2008, Tensar International Corporation, Limited LLC, Inc. 1/2PH-SPECEELDT4C08. Circle 149 • or www.SLDTonline.com/webcard 14 June 2008 Sustainable Land Development Today http://www.ctre.iastate.edu/pubs/midcon2007/McCreadyLignin.pdf http://www.tensarcorp.com/s2 http://www.tensarcorp.com/s2 http://www.SLDTonline.com/webcard

Table of Contents Feed for the Digital Edition of Sustainable Land Development Today - June 2008

Sustainable Land Development Today - June 2008 Contents Our Voice Editorial Board SLDT Resources Where Rubber Meets the Road Integrated Planning: The Key To Developing Sustainable Planned Communities Win-Win For College and Community Industry Spotlight: Transoft Unique Organization, Unique Opportunity New Preferred Provider Comments from the Austin Conference Welcome New Members New Knowledge Project Articles Books Going Green Business Management Risk Management Surveying and Mapping Industry News Products/Services Showcase Advertiser Index Classifieds The Last Word

Sustainable Land Development Today - June 2008

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