Using Foamed Asphalt as a Stabilizing Agent in Full Depth Reclamation of Route 8 in Belgrade

Maine has a variety of soil types throughout the state. A majority of these soil types degrade rapidly and have poor stability. To eliminate the cost of supplying quality road base material from a distant source and increase the stability of existing soils, the Maine Department of Transportation (MDOT) has been requiring contractors to rehabilitate roads using the full depth reclamation process. Full depth reclamation involves milling the existing bituminous pavement plus a portion of the base material. The milled material is then graded and compacted. Traffic can use the roadway until a bituminous base and wearing surface is applied. In addition to using full depth reclaimed material, MDOT has been experimenting with adding a number of stabilizing agents to virgin or recycled base materials to increase stability. Stabilizing agents utilized include cement, emulsion and calcium chloride. Foamed Asphalt is another stabilizing agent. This is a mixture of air, water and hot asphalt. Cold water is introduced to hot asphalt causing the asphalt to foam and expand by more than 10 times its original volume. During this foaming action the asphalt has a reduced viscosity making it much easier to mix with aggregates. A specialized piece of equipment mills the existing bituminous pavement and base material and introduces Foamed Asphalt all in one process. The material is then shaped to grade and compacted. Traffic can operate on the stabilized base until a hot mix asphalt base and wearing surface is applied. This paper will evaluate the performance of Foamed Asphalt over a five year period.