Pavement sections, for example, concrete slabs, of a roadway, undergo thermal movement, expansion and contraction, in response to ambient temperature changes and water permeated soil conditions. For example, thermal movement of concrete slabs in response to ambient temperature changes can be in excess of 8 mm. The slabs are purposely separated by expansion joints, which are gaps between the slabs. The gaps narrow and widen as the slabs undergo expansion and contraction. When the roadway is resurfaced, asphalt surfacing material is spread and compacted to form a continuous layer covering the slabs and the expansion joints. The gaps widen and narrow due to thermal movement of the pavement sections, which causes cracks to form in the road surfacing material. The ability of asphalt cement concrete, ACC, to withstand tensile stress is extremely limited. The gaps will penetrate through the asphalt, which causes cracks to form in the asphalt. The asphalt and the underlying pavement deteriorate quickly, especially in areas where water penetrates through cracks in the asphalt. Prior to the present invention, it was desirable to add a reinforcement membrane to the road surfacing material to deter cracks from forming.
U.S. Pat. No. 6,192,650 to Kittson et al., discloses a reinforced, asphalt-based membrane for reinforcing a road surfacing material. Numerous other membranes have been produced for small surface-area applications, such as in the patching of roads. Membranes have been proposed for reinforcing bituminous or asphalt based road surfacing materials. However, such membranes are poor in their ability to resist cracking of road surfacing material that has been applied directly over expansion joints in a concrete roadway. Accordingly, it would be advantageous to provide a road surfacing material with a more adequate membrane for resisting cracks due to underlying thermal movement of slabs separated by an expansion joint.
Another likely place for cracks to form is in a surface layer of road surfacing material that has been applied over gaps that begin as narrow crevices, as disclosed by U.S. Pat. No. 5,476,340. For example, the crevices develop in pavement sections, due to such causes as, bridge movement, earth movement and erosion. Thus, it would be desirable to cover expansion joints, crevices and other forms of gaps, with a membrane assembly. The membrane assembly would isolate the road surfacing material from movement of the pavement sections to resist cracks from forming in the road surfacing material.
USPTO Backgrounds
USPTO Backgrounds