100,000
Granite Gneiss (γd=141 pcf, w=6.2%)
Gravel (γ d=126 pcf, w=3%)
Shale (γ d=130 pcf, w=4%)
10,000
5000
100
10
4
Sum of Principal Stresses (psi)
Figure 3. Influence of material type and stress state on resilient modulus. (After Barksdale
and Itani 1994.)
ently sized aggregates: passing the 3/4-in. and retained
study was conducted to determine the moisture density
on the 1/2-in. sieve; passing the 1/2-in. and retained on
relationship of the test material. Finally, PI tests were
the 3/8-in. sieve; passing the 3/8-in. and retained on the
conducted to determine the index of the various aggre-
gate materials.
No. 4 sieve. For each size, the test involved tamping
the uniform-sized aggregate into a mold in three equal
layers using a standard tamping rod with 10 strokes per
TEST MATERIAL
layer. The tamping rod was raised to a height of 50 mm
Gravel samples were obtained from W.E. Dailey's
from the top of the aggregate surface. At the end of the
crusher plant in South Shaftsbury, Vermont, for this
third layer, material was added to ensure that the aggre-
research effort. The material consisted predominantly
gate surface was flush with the mold's rim. The test
of quartz and quartzite with lesser amounts of carbon-
was repeated using 50 strokes and the percentage of