AAPT Symposium: Sustainable Energy Use in Asphalt Production

摘要

The objective of the presentation was to answer the question – “As an asphaltcontractor what are the company objectives for using sustainable technologies?” For Granite, thesustainability goal optimizes economic (return on investment or ROI), environmental(compliance), and social (citizenship) impacts. Granite’s sustainability plan includes:1.Operation of energy-efficient asphalt production facilities on a per-unit consumptionbasis;2.Responsible use of sustainable materials technologies without compromising the qualityof the end-product;3.Increased use of recycled materials in asphalt pavements; and4.Increased use of WMA consistent with quality objectives.As an example of the economic component of the sustainability goal (ROI), Dr. Hand noted thatGranite invested in modifications to ten mixing plants to reduce losses, improve energyconsumption, reduce energy costs, and account for peak demands. Examples of improvementsincluded insulating drums and hot oil piping and installing variable frequency drives on baghousefans.The presentation also examined Granite’s use of RAP. Dr. Hand noted that RAP was initiallyseparated into three piles depending on the source. A and B piles are formed from known sources(projects) and are expected to have lower binder stiffness and good aggregate qualities – whichpermits maximized use of RAP with minimized virgin binder grades. C piles include importedRAP and is more typically used in EnviroBase. Dr. Hand also noted that fractionation of RAP wascommon as the percentage of RAP used exceeds 25%. Fractionating provides reduced variabilityand allows the use of the finer RAP fraction (<9.5 mm) which has a higher binder content(allowing a greater binder replacement).Dr. Hand also reviewed the sustainable technologies in use today including RAP, RAS, WMA,Crumb Rubber Modified mixes, and Ground Tire Rubber modified asphalt. Dr. Hand focused onWMA as an example and noted how the selection of WMA technology impacted the ROI (cost ofequipment and technology), and Compliance/Citizenship (reduced energy use and emissions)while maintaining quality (improvement of workability and attainment of density).______________________________________________________________________________