Oregon designed and constructed two types of permeable bases under both flexible and rigid pavements: an asphalt-treated permeable material (ATPM) and an open-graded aggregate material. Permeability and resilient modulus of both materials have not been determined. During pavement structural design, using the AASHTO Guide for Design of Pavement Structures, 1986, layer and drainage coefficients had to be assumed to establish pavement thickness designs. In addition, construction with the existing open-graded aggregate revealed that the material was less stable and would ravel easily under construction traffic. Results of an earlier laboratory study indicated that the current Oregon ATPM has a sufficient drainage capability, and the resilient modulus of this material is typical of the findings of other states. A modified open-graded aggregate gradation resulted, which has a higher permeability and higher resilient modulus than the existing gradation. Recommendations for implementation include selection of layer and drainage coefficients for pavement structural design and use of the proposed open-graded aggregate gradation in pavement construction. (A)
Abstract