Acceptability criteria for high fines content aggregate pavement layers
The objective of this study was to evaluate the impact of increasing fines content on the performance of unbound (unstabilized) and lightly stabilized aggregate systems. The aggregate systems analyzed varied in the amount of mineral fines, the moisture state during curing and at the time of testing, and the amount of Portland cement used to stabilize the blend. The evaluation was based on measurements of anisotropic resilient properties, permanent deformation, and unconfined compressive strengths of aggregate systems. In addition, the nonlinear anisotropic resilient properties of the aggregate blends were used in a finite element program to determine critical pavement responses. Aggregate systems with higher fines contents were, as expected, more sensitive to moisture than control systems with standard fines contents. The increase in the fines content in the unbound systems when molding moisture was greater than optimum dramatically diminished the quality of performance. However, the aggregate systems with higher fines benefited considerably from low percentages of cement stabilizer. Researchers found that with the proper design of fines content, cement content, and moisture, the performance of the stabilized systems with high fines content can perform equivalent to or even better than systems with standard fines content. This was clearly demonstrated that by enhancing the resilient properties (an increase in stiffness and a decrease in the level of anisotropy), permanent deformation of the aggregate systems were significantly reduced. This finding was in conformity with unconfined compressive strength of lightly stabilized high fine systems.