Sustainable reuse of coarse aggregates in clay-based impervious core: Compactability and permeability

Abstract

The reuse of coarse aggregate (CA) on clay-based materials is a sustainable and cost effective solution to minimize the extraction of natural farmland resources and reinforce the mechanical behaviour of impervious materials. However, limited knowledge is available regarding the compactability and permeability of CA-clay mixtures and their intrinsic connections. This study reports the results of a series of modified dynamic compaction tests and triaxial permeability tests performed on impervious clay materials reinforced with various contents of CA. Results demonstrate that compaction behaviour of CA-clay mixtures changes significantly with coarse aggregate content (Cg). A peak value of global maximum dry density is achieved at Cg = 70%, while the fine clay matrix is compacted to its densest state when Cg<30%. The permeability, as a good indication of meso-structure in CA-clay mixtures, is significantly dominated by coarse aggregate content as well as the clay matrix void ratio. From the perspective of preferential flow path concept, permeability reaches a lowest value at Cg = 30%. Due to the clay bridge effect induced by the heterogeneous density field, the larger the coarse particle size is, the smaller the permeability coefficient will become.