Part 3: Evaluation of Soaking Methods
for AASHTO T 85 and T 84 Using In-Situ
Moisture Samples
Figure 3-24 shows the procedures for testing coarse aggregates.
As shown in Figure 3-24(a), aggregate samples were
oven-dried and then soaked for 15 hours before testing. In
Figure 3-24(b), samples were tested in their in-situ moisture
conditions and vacuum-soaked up to 15 minutes before
testing.
Testing of fine aggregates was different depending on the
P200 content and composition. Based on results of Experiment
4 presented later in this report, the P200 should be
tested separately according to ASTM C110, Section 21 or
ASTM D5550 if the sand equivalent (AASHTO T 176) value
of the fine aggregate is less than 75. Thus, two test procedures
for fine aggregates are shown in Figures 3-25 and 3-26, as
follows:
• The Preston sandstone (sand equivalent is 26.1 percent) and
RC Limestone (sand equivalent is 39.2 percent) materials
were tested according to the procedure shown in Figure 3-25
in which the P200 materials should be tested separately.
• The Arkansas natural sand (sand equivalent is 100 percent),
Blast Furnace Slag (sand equivalent is 86.5 percent),
and Texas limestone fine aggregate (92.8 percent) were
tested without separating the P200 materials.
• Instead of drying and then soaking samples for 15 hours,
as shown in Figure 3-25(a) and Figure 3-26(a), the samples
can be tested in their natural moisture conditions and vacuum
soaked for much less time, as shown in Figure 3-25(b)
and Figure 3-26(b).
For Part 3, four combinations of drying and soaking
methods were tested. In the first combination (control), the
aggregate samples were oven-dried and soaked for 15 hours
as specified in AASHTO T 84 and T 85. The other three combinations
were a combination of one natural moisture condition
and three vacuum soaking periods. For each material,
14 replicates were prepared. Four sets of three replicates were
randomly selected for testing based on the four combinations
of drying and soaking methods. The random selection was
carried out to make sure there was no bias toward any sets of
replicates or the order in which the samples were prepared.
The remaining two samples were kept in reserve.
The in-situ water content and water absorption capacity of
the aggregates are presented in Table 3-29. For production of