Using Foamed Asphalt as a Stabilizing Agent in Full Depth Reclamation of Route 8 in Belgrade [February 2002]
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2002-02-01
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Abstract:Maine has a variety of soil types throughout the state. Most 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. Some of the stabilizing
agents 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 graded and compacted. Traffic can
operate on the stabilized base until a hot mix asphalt base and wearing surface is applied.
This paper will describe the steps involved to design a foamed asphalt mix, preparation of the roadway,
and evaluation of the experimental application
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