Lesson 1/Learning Event 2
Asphalt Cutback
For liquid asphalt use the following equation:
P
=
0.02(a) + 0.07(b) + 0.15(c) + 0.02(d)
where
p
=
percent of residual asphalt by weight of dry aggregate
a
=
percent of mineral aggregate retained on #50 sieve
b
=
percent of mineral aggregate passing #50 sieve and retained
on #100 sieve
c
=
percent of mineral aggregate passing #100 sieve and retained
on #200 sieve
d
=
percent of mineral aggregate passing #200 sieve
It should be noted that this equation provides only initial guidance for selection of bitumen content.
Laboratory tests are required to determine a design bitumen content. Further adjustments in bitumen
may be necessary in the field.
Asphalt Emulsion
Use Table 2 for an estimate of the emulsified asphalt requirements.
In-place mixing of the soils and stabilizing agent is permissible; however, it should be recognized that
plant mixing will produce a more uniform product. Although the soil strength is upgraded, no reduction
in the pavement thickness is normally permitted. However, should the stabilized soils meet the
requirements for the subbase material, and exceed four inches in thickness, then the equivalency factor
may be applied.
TABLE 2. EMULSIFIED ASPHALT REQUIREMENTS FOR SUBGRADE STABILIZATION
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