P-155 lime-treated subgrade
Table 2. Division of FAA materials into stabilized
P-155 lime-treated subgrade is a mixture of
and unstabilized categories.
soil, lime, and water. Hydrated lime is specified.
P-208 aggregate base
P-208 aggregate base course is a mixture of
Soilcement base course
Aggregate base course
clean stones or gravel blended with sand, stone
Cement-treated base course
Crushed aggregate base course
dust, or other binding or filler materials. The
Econocrete subbase course
Sandclay base course
coarse portion of the material can be either
crushed or uncrushed. Crushed coarse aggregate
can be either crushed gravel, crushed stone, or
Lime rock base course
crushed slag. Any fines obtained from the crush-
Shell base course
ing of the coarse aggregate are used in the fine
portion. Uncrushed fine material can be added.
At least 30 to 65% (depending on the maximum
particle size) of the material retained on the no. 4
FAA material specifications
sieve shall have at least one fractured face. Three
The base course materials in Table 1 were
gradation limits for this material are shown in
divided into stabilized and unstabilized materi-
Figure 1b. As with the subbase course material,
als as shown in Table 2. A brief description of each
the material has a liquid limit of less than or equal
of the materials is presented.
to 25% and a PI of no more than 6%.
P-154 subbase course
P-209 crushed aggregate base
The P-154 subbase course material is a blend of
The gradation of the P-209 crushed aggregate
coarse aggregates and either fine sand, clay, stone
base course is shown in Figure 1c. The gradation
dust, or other similar binding or filler materials.
for the P-208 aggregate base course is also shown
The bounds for the subbase course material are
in the figure for comparison. Although they are
shown in Figure 1a. The material has a liquid
both could be considered crushed aggregate
limit of less than or equal to 25% and a Plasticity
bases, the P-209 is different from the P-208 aggre-
Index (PI) of no more than 6%. An additional
gate base material in the following manner. First,
specification was identified for use of this mater-
although the coarse portions of the gradations are
ial in cold regions, i.e., the amount of material
alike, the fine portions are different. The maxi-
finer than 0.02 mm must be less than 3%.
U.S. Standard Sieve Numbers
P-154 Subbase Course
Grain Size (mm)
Silt or Clay
a. P-154 subbase course.
Figure 1. Grain size distribution limits.