Civil Engineering Reference
In-Depth Information
a temperature below this without becoming a fire hazard. The Cleveland
open cup method (ASTM D92) requires partially filling a standard brass cup
with asphalt cement. The asphalt is then heated at a specified rate and a
small flame is periodically passed over the surface of the cup, as shown in
Figure 9.14. The flash point is the temperature of the asphalt when the volatile
fumes coming off the sample will sustain a flame for a short period of time.
The minimum temperature at which there are sufficient volatile fumes to
sustain a flame for an extended period of time is the fire point.
Rotational Viscometer Test
The rotational (Brookfield) viscometer test
(ASTM D4402) consists of a rotational coaxial cylinder viscometer and a tem-
perature control unit, as shown in Figure 9.15. The test is performed on un-
aged binders. The asphalt binder sample is placed in the sample chamber at
135°C (275°F); then both are placed in the thermocell. A spindle is placed in
the asphalt sample and rotated at a specified speed. The viscosity is deter-
mined by the amount of torque required to rotate the spindle at the specified
speed. The spindle size used is determined based on the viscosity being mea-
sured. The viscosity is computed in centipoises (cP) by the testing machine.
The Performance Grade specification limit is stated in Pascal seconds
which is equal to cP divided by 1000. The viscosity is recorded as the aver-
age of three readings, at one-minute intervals, to the nearest In ad-
dition to testing at the temperature required by the specification, additional
tests are performed at higher temperatures to establish the temperature
susceptibility relationship used to determine the compaction and mixing
temperatures required for the mix design process.
Pa
#
s
1
2
,
0.1 Pa
#
s.
Dynamic Shear Rheometer Test
The dynamic shear rheometer test system,
Figure 9.16, consists of two parallel metal plates, an environmental chamber,
a loading device, and a control and data acquisition system (AASHTO T315).
The dynamic shear rheometer is used to measure three specification re-
quirements in the Performance Grading system. For testing the neat binder
Thermometer
Small flame
Stop valve
FIGURE 9.14
Cleveland open cup
flash point test apparatus.
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