UFC 3-250-03
15 May 2001
CHAPTER 5
ASPHALT STABILIZATION
1. GENERAL. This chapter contains information for use of asphalt cement for stabilization of
soil/aggregate materials and on stabilization of drainage layers. When any subsurface layer receives an
asphalt treatment, the treatment will be considered asphalt stabilization. In general, asphalt stabilization
is utilized where good base course materials are not readily available and where the existing subgrade
materials are sands or silts suitable for stabilization. Technical Manual TM 5-822-4/AFM 88-7, chap. 4
(Future AFJMAN 32-1019) contains detailed information on the design and construction of asphalt
stabilized soils.
2.
MATERIALS.
a. Soil/aggregate. There are a number of requirements for determining soil suitability for asphalt
stabilization. The stabilization of fine-grained soils depends on the plasticity characteristics and amount
of material passing the 75 Fm (No. 200) sieve. Table 5-1 lists a recommended gradation of materials for
asphalt stabilization. Soils with high plasticity are not stabilized with asphalt because of difficulty in
thoroughly mixing the asphalt into the soil. These soils can only be stabilized if pretreated with lime or
cement to decrease the plasticity of the soil.
b. Asphalt. The asphalt used for stabilization may be either emulsified or cutback asphalt.
Normally, the emulsions used are slow setting (SS) or possibly some medium setting (MS) emulsions.
Rapid set (RS) emulsions are not used. Any type of cutback from rapid (RC) to medium (MC) to slow
(SC) cure can be used for asphalt stabilization. The use of emulsions versus cutbacks is dependent on
the availability of materials, soil type, climate, and construction practice. The availability of cutbacks may
be limited in some areas due to environmental concerns.
Table 5-1
Recommended Gradations for Asphalt-Stabilized Subgrade Materials
Sieve Size
Percent Passing
76.2 mm (3 inch)
100
4.75 mm (No. 4)
50-100
600 Fm (No. 30)
38-100
75 Fm (No. 200)
2-30
3. COMPOSITION AND MIXTURE. For stabilized materials, the type of asphalt used can be as
important as how much is used. TM 5-822-4/AFM 88-7, chap. 4 (Future AFJMAN 32-1019) contains
information on the type and amount of liquid asphalt to use. Design procedures for determining optimum
asphalt content are given for both cutback and emulsified asphalts.
4. CONSTRUCTION. Methods and procedures for constructing asphalt stabilized materials are given
in TM 5-822-4/AFM 88-7, chap. 4 (Future AFJMAN 32-1019).
5. DRAINAGE LAYERS. Guidance for the design and construction of subsurface drainage features is
given in TI 825-01/AFM 32-1124(I)/NAVFAC DM 21.10. Open graded material (OGM) is the drainage
5-1
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