Sustainable Application of Unbound Quarry Byproducts in Pavement Construction through Aggregate Gradation Optimization

Abstract

Unbound aggregates are becoming increasingly scarce and expensive due to the loss of rock quarries and gravel mines to other land uses; therefore, it is important to engineer and optimize aggregate gradations for the targeted end-performance. This paper is aimed at validating in the laboratory a newly introduced gradation design concept intended for controlling structural assembly strength (stability) and drainage characteristics (field drainability). Aggregate gradation optimizations were studied for blending and mixing proportions of fine granite tailings (FGT), a typical crushed granite mining byproduct that has long been considered “waste” materials, and coarse crushed granite aggregates (CCGA). To this goal, one of the common quarry byproduct wastes (i.e., FGT), was mixed with CCGA in varying percentages to explore their potential use for building pavement foundations. Large-scale monotonic triaxial compression tests were performed to investigate the effects of blending proportions on the stress-strain behavior. Based on the test results, the optimum aggregate gradations recommended by the new gradation design concept provided enhanced stability without compromising drainability. The new gradation design concept, hence validated in this study with produced optimum gradations, is expected to achieve sustainable and beneficial unbound aggregate applications for cost-effective longlife pavements.