SHRP-A-379 traducir

6.5.1 For analog strip-chart recording equipment, the deformation recorder trace
must be of sufficient magnitude and time resolution to enable accurate data reduction.
Resolution of each variable should be better than 2 % of the maximum value being measured.
The trace shall have sufficient contrast to the background so that it may be reproduced in
reports. At all times, the minimum resolution of the trace must be maintained at 2% of the
maximum value of the recorded parameter.
6.5.2 For digital data acquisition systems, the minimum sampling frequencies for the
1,000-second creep test are as follows:
• 100 Hz for the first 10 seconds
• 1 Hz for the next 5 minutes (up to 300 seconds)
• 0.2 Hz through the remainder of the test (remaining 700 seconds)
For the indirect tensile strength test, which is performed immediately after the creep
test and uses a stroke rate of 13 mm per minute, a sampling frequency of 20 Hz is used
through the entire test (see note 2).
NOTE 2.--Experience has shown that a 16-bit A/D board is required to obtain both the resolution needed in
the creep test and the range for the strength portion.
6.5.3 When a digital data acquisition system is used, a special conditioner is
required. This special conditioner shall have the following characteristics.
• An excitation frequency of 2.9 to 20 kHz
• An excitation voltage of 1 V
• A load independence of 30 ohms
• An output + 10 V
• A noise level less than 2.5 × 10-4 mm measured at output of the conditioner when
+ 10 V equals + 2.5 mm
• A filter cut-off greater than 5 Hz
6.6 Oven--The oven for the preparation of hot mixtures shall be capable of being set
to maintain any desired temperature from room temperature to 163°C.
6.7 Mounting Template--A mounting template, as shown in figure 1, is used to place
and mount the eight brass gauge points to each side of the test specimen (four per side).
6.8 Specimen Loading Frame--The specimen load frame shall be capable of
delivering test loads in good alignment and with minimal friction (less than 2.27 kg
resistance) in guides or bearings even when eccentric loads occur (caused by slightly uneven
specimens, temperature changes, etc.) (see note 3). Loading platens shall have a width equal
to D/8, where D is the standard diameter of the test specimens, and a radius of r -- D/2.
NOTE3.--Often a smaller guide frame with special alignment capabilities is used in conjunction with the
larger loading flame to accomplish this, as portrayed in figure 2.
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