Create successful ePaper yourself
Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.
8. PROCEDURE<br />
8.1 Measure the bulk specific gravity of each test specimen in accordance with<br />
AASHTO T166 or T275, whichever applies (note 8).<br />
NOTE 8.--If the bulk specific gravity of the test specimens is measured in accordance with AASHTO T166,<br />
the specimens must be allowed to dry prior to testing and preconditioning. Moisture or water trapped in the<br />
permeable voids can have an effect on the test results. Retaining the specimens in the temperature cabinet for<br />
12 hours should be sufficient to allow the moisture to evaporate from the permeable voids.<br />
8.2 After the specimens become dry, place the test specimen in a controlled<br />
temperature cabinet and bring it to the specified test temperature. Unless the temperature is<br />
monitored and the actual temperature known, the specimen shall remain in the cabinet at the<br />
specified test temperature for at least 12 hours prior to testing.<br />
8.3 Measure the height and diameter of the specimen to the nearest 2.5 mm. Height<br />
or thickness and diameter measurements shall be made at 1/3 points and the values averaged<br />
for use in any calculations.<br />
8.4 Mounting LVDTs on the Specimen's Surface<br />
8.4.1 Transducers shall be mounted about the center of fiat faces of diametral<br />
specimens, with a gauge length equal to one-fourth the specimen's diameter. They should be<br />
mounted so that the transducer's centerline is no more than 6 mm above the specimen's<br />
surface. Measurements shall be taken in both horizontal and vertical directions on both sides<br />
of the specimen.<br />
8.4.2 One such system that has been used successfully is shown in figure 3. The<br />
displayed system uses a brass mounting apparatus clamped onto brass gauge points. The<br />
gauge points are 8 mm in diameter by 3 mm thick and are placed on the specimen with<br />
epoxy and a specially designed gauge point template (see figure 3 and note 9). One piece of<br />
the mounting apparatus holds the LVDT's transformer securely, while the other piece<br />
suspends the core of the LVDT. Both pieces clamp securely to the gauge points with set<br />
screws.<br />
NoTE 9.--The two-piece mounting apparatus shown in figure 3 was designed to be used with sub-miniature<br />
LVDTs and is machined from a 12-mm diameter brass rod.<br />
8.5 Precondition the room-temperature specimens by one of the following procedures<br />
for different equipment.<br />
8.5.1 For a closed-looped electrohydraulic system. Apply 100 cycles of haversine<br />
load with amplitude equivalent to 70 kPa tension. One load cycle shall consist of 0.1 seconds<br />
of haversine loading and 0.9 seconds of zero-load condition. The amplitude of the load may<br />
be calculated by<br />
P = 11 ×<br />
104tD<br />
127
Change language