TM 5-822-7/AFM 88-6, Chap. 8
Table 4. Deleterious materials in coarse aggregates for airfield and heliport pavements.
Areas with
Areas with
Minor Popouts
Major Popouts
a
a
a
Severe a
Moderate
Severe
Moderate
Weather
Weather
Weather
Weather
Materials
2.0
2.0
0.2
0.2
Clay lumps
1.0
1.0
b
0.1
0.2
Shale
1.0
1.0
0.5
0.5
Material finer
c
than No. 200 sieve
0.2
0.5
0.5
Lightweight
particles
0.2
Clay ironstone
0.1
0.5
1.0
1.0
(Continued)
a
Severe, moderate, and mild weather are defined as follows:
Average Precipitation for a Single
Air Freez-
ing Index
Month During Period--1 Month Before
Weather
for Coldest
Average Date of First Killing Frost
to Average Date of Last Killing Frost
Year in 30*
Severity
Any amount
Moderate
500 or less
Less than 1 inch
Moderate**
501 or more
1 inch or more
Severe
501 or more
* Calculated as described in TM 5-818-2/AFM 88-6, Chapter 4.
** In poorly drained areas, the weather should be considered severe
even though the other criteria indicate a rating of moderate.
b
Shale is defined as a fine-grained thinly laminated or fissile sedimentary rock.
It is commonly composed of clay or silt or both. It has been indurated by compac-
tion or by cementation, but not so much as to have become slate.
c
Limit for material finer than No. 200 sieve will be increased to 1.5 percent for
crushed aggregates if the fine material consists of crusher dust that is essen-
tially free from clay or shale.
d
The separation medium shall have a specific gravity of 2.0. This limit does not
apply to coarse aggregate manufactured from blast-furnace slag unless contamination
is evident.
e
Clay ironstone is defined as an impure variety of iron carbonate, iron oxide,
hydrous iron oxide, or combinations thereof, commonly mixed with clay, silt, or
sand. It commonly occurs as dull, earthy particles, homogeneous concretionary
masses, or hard shell particles with soft interiors. Other names commonly used for
clay ironstone are "chocolate bars" and limonite concretions.
7
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