Influence of Recycled Asphalt Pavement Content on Air Void Distribution, Permeability, and Modulus of Base Layer

Abstract

The use of recycled materials for construction is beneficial to both the environment and the economy. Reclaimed asphalt pavement (RAP) is one of the most commonly used recycled materials. State departments of transportation allow its use in unbound base materials at different percentages. The modulus and the permeability are recognized as important parameters for base course materials because of their effect on pavement service life. Determining the effects of the percentage of RAP on the modulus and permeability of base materials that contain RAP is important for proper pavement design. This study evaluates the effects of RAP percentage on the resilient modulus and the permeability of unbound base materials. Increasing the RAP percentage increased the resilient modulus. Constant-head permeability test results indicated that increasing the RAP percentage decreased the coefficient of permeability. High-resolution X-ray computed tomography was used to study the internal structure of the test specimens. RAP mixtures had lower void ratios than virgin crushed aggregate, which explained the high resilient modulus and low permeability of RAP mixtures.