Submitted to The Arizona Highway Department Phoenix, Arizona for Research Project - Arizona HPR-1-14(167) / The research has been directed toward obtaining information on some of the physical properties of various asphalt- rubber (A-R) mixes as related to waterproof membrane applications. In particular, three rubber particle size distributions and three asphalt-rubber spread quantities were investigated. Laboratory testing utilized for physical property determination included thin film permeability, water absorption (ASTM D570-72), Water Vapor Transmission (ASTM E96-72, procedure BW), ductility (ASTM D113-74), Tensile-Toughness, viscosity and slope stability. The results of the study showed that the A-R as an integral membrane is relatively impermeable. The addition of the rubber does not affect the permeability of an otherwise homogeneous asphalt film. Physical property values of asphalt that are increased when rubber is added include water absorption, slope stability, toughness and viscosity. Those that exhibit lower physical property values include ductility and slope/flow characteristics. Installation of experimental field plots provided additional positive information on the waterproofing characteristics of the A-R and also helped develop field procedures on A-R application to a prepared subgrade.