EVALUATION AND GUIDELINES FOR DRAINABLE BASES

Base materials are normally selected to achieve maximum density, and to possess enough stiffness and strength to carry the traffic loads. The poor drainability of these materials has been of concern. This report describes the characterization of base materials being commonly used throughout the State of Texas. This includes the characterization of stiffness and strength based on the resilient modulus and the static strength of compacted specimens. The drainability is evaluated based on the permeability coefficient and the water retention capacity. The water retention test was found to be easier to perform and it is believed to be more directly related to the drainability of the compacted base than the permeability test. Alternative materials evaluated consisted of open-graded bases and cement-stabilized gravel. The results of the present study indicate that cement stabilized gravel is the best alternative to achieve high stiffness and strength and at the same time minimize water retention capacity of the compacted base. Guidelines for design and construction of base layers are proposed based on properties of cement-stabilized gravel.