Mechanical Properties of Aggregates for Roadbase Partially Replaced with Reclaimed Asphalt Shingles

Abstract

The objective of this research is to evaluate the potential to partially replace the natural aggregates used for roadbase with reclaimed asphalt shingles (RAS). Three percentages of replacement were evaluated, namely 10, 20, and 30%. A control mix without RAS was tested for comparison. The physical properties of the mixtures, including particle size distribution, soundness, and abrasion were measured and compared with local material specifications. Additional laboratory testing to determine the compatibility (ability to achieve compaction), bearing strength, permeability, and shear strength were conducted. Overall, the mixtures would still meet the requirements for particle size distribution, soundness, and abrasion. The mixtures with RAS had a lower dry unit weight and higher optimum moisture content than the control. However, the addition of RAS to the natural aggregates could result in an exponential decrease in its bearing strength. RAS also reduced the permeability of the material. A replacement of 10% natural aggregates with RAS resulted in a 50% reduction in the California Bearing Ratio and an approximate reduction of 80% in the coefficient of permeability. Results from large-scale direct shear also show an increment in the cohesion and a decrease in the internal friction angle with the addition of RAS. A replacement of 10% natural aggregates with RAS resulted in a 20 kPa increase in cohesion, whereas the control material was cohesionless, and a reduction of 20% in the internal friction angle. Overall, it was concluded that replacements of natural aggregates with more than 10% RAS are not recommended for materials similar to those used in this study.