5. Surface Preparation
5.1 Introduction
The performance of an asphalt mixture under traffic is directly related to the condition of the surface on which the pavement layers are placed. For a full-depth asphalt pavement, if the condition of the subgrade soil is poor (particularly if it is wet and rutted under the haul trucks), the ultimate life of the roadway may be significantly reduced. For asphalt layers placed on top of a new, untreated granular base course, that base material should be stable, the surface should be dry, and the base should not be distorted by the trucks carrying mix to the paver. For mix laid on top of existing asphalt layers, that surface should be properly prepared, with all distresses and defects repaired and the surface cleaned. A tack coat should also be used to ensure a bond between the existing pavement surface and the new asphalt overlay. When asphalt mix is placed over a Portland cement concrete (PCC) pavement, the PCC surface should be properly prepared and a tack coat applied.
The performance of an asphalt mixture under traffic is directly related to the condition of the surface on which the pavement layers are placed.