Assessing the Variation in Cutback Asphalt Requirement for Various Geotechnical Properties of Asphalt Stabilized Soil

Abstract

The subgrade layer must be strong to resist shear failure, tensile stresses and have adequate stiffness to avoid and resist excessive pavement deformation. Available fill materials do not always meet these requirements and may require improvement of their engineering properties, soil stabilization with liquid asphalt may be an alternative to improve the stability, adhesion and waterproofing properties which are desired for embankment construction purpose. The soil in this investigation represents typical subgrade soil usually used for embankment construction by Mayoralty of Baghdad. The variation in cutback asphalt content requirement for various geotechnical properties of asphalt stabilized soil was investigated. The optimum cutback asphalt content was determined by using direct shear test, one dimensional confined compression test and unconfined compressive strength test. Such properties are considered as good representative of the actual stresses that embankment usually practice under vehicles load. Testing was carried out at both dry and absorbed conditions. It was concluded that the optimum fluid content was 15% (6% cutback asphalt + 9% water) at dry and soaked condition for the direct shear test and one dimensional confined compression test, while it was 3% at dry condition and 12% at absorbed condition for the unconfined compressive strength test.
Keywords: Cutback asphalt, unconfined compression, consolidation, direct shear, subgrade