Reinforcing Spent Coffee Grounds for Geotechnical Applications

Recent studies demonstrated the use of spent coffee grounds (CG) in geotechnical engineering applications. These studies focusing on chemical stabilization of CG using by-products and traditional binders as cement and lime. However, reinforcing CG with synthetic fibers has not been reported in the current literature. Thus, this paper demonstrates the efficiency of reinforcing CG using polypropylene fibers in 0.5% by weight. Compaction tests reveal that CG alone does not achieve good compaction properties (i.e. high maximum dry density and high optimum moisture content). Given this, a silty soil was added by weight (i.e., 25%, 50%, and 75%) to stabilize granulometrically the CG grains before reinforcing them with the fibers. The results showed an increase of unconfined compressive strength (qu or UCS) of CG-silt-fibers compacted blends in 80% comparing to CG-silt blends. Further, MDD of CG increase from 4.16 kN/m3 to 10.38 kN/m3 by the addition of 75% silty soil. For the potential use of fiber-reinforced CG in geotechnical earthworks, it is recommended to use at least 50% silty soil to improve the compaction and mechanical properties of blends.