When a pavement surface begins to develop widespread surface cracking due to subgrade failure, an asphalt fabric overlay is a reliable alternative to costly excavation and replacement of the cracked and deteriorated asphalt.
Most subgrade failures arise from surface water seeping down into the pavement's aggregate base course and weakening the foundation soil's shear strength. Once this occurs, it is not long before surface cracking appears due to the weight placed on the pavement over this weak foundation. Simply placing a layer of slurry seal. over these cracks will only provide a very temporary solution, as reflective cracking will soon take place.
Reflective cracking is a situation in which the cracks covered by new layers of slurry or asphalt make their way back up to the surface. Although it is bound to happen, the reflective cracking takes much longer if an asphalt fabric overlay is utilized rather than a simple slurry seal.
The geo textile fabric will create a moisture barrier that will prevent water from passing through cracks, joints, and the porous pavement itself, keeping the aggregate base course and foundation soil intact and strong.
It will also absorb much of the energy normally transferred from cracks in the old pavement into the new asphalt overlay by its sheer resistance and ductility. These functions are paramount in preventing reflective cracking as well as surface deflections and potholes.
An asphalt fabric overlay is begun by cleaning the existing surface of dust, dirt, vegetation, and moisture. In some instances large cracks are sealed to improve the performance of the fabric by supporting it underneath. A layer of PG6422, a hot, viscous liquid asphalt, is applied at a fairly heavy volume of .2 gallons per square yard. Then, while the PG6422 is still hot, the geo textile fabric is rolled on to the surface with the use of special application equipment. Wrinkles are smoothed out and then it is ready to be paved over. A minimum of 1.5 inches of asphalt is applied and compacted. During the paving process, the PG6422 melts from the heat of the new asphalt, and the compaction forces cause the PG6422 to soak through the fabric. This creates a waterproof membrane that effectively adheres to both the new and old asphalt pavements.
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