Renewable Paving Binders from Top-lit Updraft Kilning of Biomass

North Carolina State University, Raleigh NC

Investigators

Abstract

The long-term goal of this research is to develop a renewable alternative to asphalt binder in pavements while maintaining or improving performance over conventional binders. This project will study bio-binders produced as a by-product of top-lit updraft kilning (TLUK) of biomass to replace asphalt. TLUK is currently under study primarily for the production of syngas and bio-char but also generates a heavy-oil like liquid waste, called tar in biomass gasification. This project will lead to improved methods for producing paving binders from processing of biomass, advancing sustainable civil infrastructure design and reducing paving costs which have risen dramatically in recent years. The objective of this project is to test the hypothesis that the selection of biomass feedstock, TLUK operating conditions, and modifiers can be aligned to yield a bio-binder with properties and performance comparable to petroleum-based asphalt and that reduces energy use and emissions over the life of the pavement. Through exploring multiple feedstock sources, including corncobs (agriculture residual), switchgrass (perennial grass), and woodchips (woody biomass), and varying TLUK operational parameters, this research will link production methods to bio-binder yield and quality. This, in turn, will advance knowledge regarding production of bio-renewable alternatives to asphalt. Additionally, the research will explore improvement of bio-binder performance through modification by polymers, which have been successfully utilized in petroleum-based asphalts. A multi-scale approach will be taken to best engineer bio-binders. Fundamental characterization of bio-binders composition and microstructure will be performed and linked to production parameters. Macroscale performance of bio-binder cohesive and adhesive properties will be measured and qualitatively linked to composition. In addition, bio-binder aggregate mixtures will be produced to assess constructability and performance. Critical properties for qualifying bio-binders for use in pavements will be identified through comparison between bio-binder properties and mixture performance. Life cycle assessment will be conducted for the processes associated with bio-binder production, use in pavement, and pavement end-of-life management to assess and enhance the sustainability compared to conventional asphalt pavements.