| The lack or improper operation of pavement subsurface drainage systems has long been known to greatly decrease the service life of pavement. To minimize premature pavement distress, it is imperative to provide adequate drainage to allow for accumulated water to drain out from the base and subbase, thus avoiding saturation of base and subgrade soils. Ohio Department of Transportation (ODOT) has adopted several types of materials specifications for use as permeable bases: (a) ODOT 307 base, including IA, NJ, and CE types, (b) ODOT 306 Cement Treated Base, and (c) ODOT 308 Asphalt Treated Base. However, the effectiveness of these permeable base materials has not been conclusively established in previous ODOT studies. Furthermore, there have been no prior studies on the durability and resistance to permanent deformation of these materials. Therefore, the main objective of this study was to evaluate the behavior of different drainable base and subbase materials used by ODOT. The study was based on extensive laboratory work focusing on the characteristics of structural stability and hydraulic conductivity. Different factors affecting the permeability and resilient modulus were included in the study, such as material types, aggregate gradations, stabilization agents, freezing/thawing cycles, degree of saturation, temperatures, and soaking. Drainage capability of the pavement built at ATP.90 instrumentation/monitoring project site with these drainable base materials was also analyzed using pavement design software. Several resilient modulus models were fitted with the experimental data to determine the most suitable one providing best fit. The permanent deformation behavior of the base materials and the asphalt concrete layer was modeled with emphasis on the effects of stress level, number of load cycles, and temperature.; The hydraulic conductivity test results indicated a wide range of hydraulic conductivity within the gradation used by ODOT. Nevertheless, all the materials satisfy the drainage criteria, except the ODOT304 with fine grading. The resilient modulus results indicated that open graded material has a higher stiffness than the dense graded. The permanent deformation empirical model has shown to predict well the permanent strains at any stress condition and any number of cycles for unbounded aggregate, asphalt stabilized base and asphalt concrete. The research results will provide essential information to assist ODOT engineers in selecting the best base and subbase materials with good permeability and stability characteristics. It also provides important material characterization information to help in assessing the performance of the long-term monitoring of pavements at the ATB.90 project site. |
