The time frame was to finish approximately half of a mile of flexible pavement roadway in January 2003. Country Trail and Marvino Lane are major collector roads that servie over 300 homes and a strip mall. To make things more difficult, the area's natural soil deposits contain high levels of silt which would be a major problem for the life of flexible pavements.
The Design
Due to possible discrepancies in the subgrade soils, especially during construction in the winter months, the city required the contractor to use a biaxial geosynthetic placed under the 8-inch of graded aggregate base course which is normally required. Unlike stabilization applications, there would be very little stress caused in the geosynthetic installation. Applying the high tensile modulus geosynthetic that also separates would offer additional benefits in the pavement when the subgrade soil softens and loses support over time.
Construction
The condition of the majority of the subgrade soil seemed to be firm during the construction of the flexible pavement. Utilizing wide rolls of Mirafi® HP370 would allow the contractor to place panels three-wide with the needed amount of overlapping on these collector roads. Using TenCate Mirafi® geosynthetics allowed the contractor to keep the flexible pavement construction schedule for the project on time.
Follow-Up
At the end of the original case study, photos were taken of the represented area on Country Trail where the geosynthetic was used along with a section of Parkstone Drive which was constructed 6 months earlier without geosynthetic.
In February 2011, the same areas were inspected and new photos taken to record any changes in the roads. In the areas of Country Trail and Marvino Lane that had installed Mirafi® HP370, there were no signs of deterioration. The asphalt did show some wear but nothing that indicated deterioration of the subgrade or any base course issues.
On the other hand, Parkstone Drive which was constructed without geosynthetic continued to deteriorate. It seems a section of the pavement had been replaced and areas adjoining the repairs are starting to show signs of fatigue. A different section of pavement showed signs of early deterioration further into the development of Country Trail Road beyond where the geosynthetic was used. This section of Country Trail was constructed a year after the first pavement areas that used geosynthetics.
