13-468, TR-656, SPR 90-00-0646-000
Federal Highway Administration State Planning and Research Funding
Iowa Department of Transportation
Iowa Highway Research Board
Stine Seed Company of Iowa
About the research
Rapid advancements in bioenergy-based industry have not only reduced our dependency on fossil resources but also brought about sustainable development for human society. The production of biofuel derived from biomass also produces co-products containing lignin. Biofuel co-products (BCPs) containing sulfur-free lignin were investigated in this research study to gain further insight into their benefits in stabilizing pavement subgrade soil. Four different types of co-products were tested: (1) an oily liquid type with medium lignin content (BCP A), (2) a powder type with low lignin content (BCP B), (3) another oily liquid type with high lignin content (BCP C), and (4) an oily liquid type of lignin derived from paper pulp production (lignosulfonate). The laboratory tests focused on engineering properties, including unconfined compressive strength (UCS), shear strength, freeze-thaw durability, and moisture sustainability of BCPs-treated soils. Four types of Iowa soil were mixed with BCPs and lignosulfonate for testing, and the results indicated that BCPs are more promising additives for soil stabilization in Iowa because of their beneficial effects in improving soil engineering properties, strength properties, durability, and resistance to moisture degradation. Scanning electron microscope (SEM) and x-ray diffraction (XRD) analyses were also performed to identify mechanisms of lignin-based soil stabilization. A microstructural analysis showed that lignin materials could coat and bind soil grains and thereby form a strong soil structure.
Five soil stabilizers (cement, lignosulfonate, chlorides, Claycrete, and Base One) were sprayed on a gravel road subgrade for the field demonstration. In situ tests including light weight deflectometer (LWD) and dynamic cone penetration (DCP) were performed before, one week after, and one year after the construction to monitor the performance of the stabilized sections and to draw the lessons learned from the practice. The construction process was documented both visually and in written form. Some critical lessons were learned, which provide recommendations for future studies and benefit relevant practitioners. Based on this study’s findings, the application of BCPs in soil stabilization appears to benefit both the bioenergy industry and the pavement construction industry.