AASHTO TP 140-20 pdf free download

AASHTO TP 140-20 pdf free download.Moisture Sensitivity Using Hydrostatic Pore Pressure to Determine Cohesion and Adhesion Strength of Compacted Asphalt Mixture Specimens.
SUMMARY OF TEST METHOD
Asphalt mixture specimens are prepared using the methods described in R 68, T 247 or T 312. The bulk specific gravity (G,,1h) of each specimen is measured using T 166 or T 331. A subset of specimens is moisture conditioned by exposing them to moisture at high temperature for 20 hours to test for adhesion strength and then using cyclically increasing and decreasing hydrostatic pore pressure to test for cohesion strength. After conditioning, the Gmh of each specimen is measured and compared to the Gth obtained prior to conditioning to determine the swell or change in bulk specific gravity of the specimen. Then, the tensile strength is measured for each conditioned and unconditioned specimen. The tensile strength ratio (TSR) for these specimens is calculated to evaluate the effect of moisture damage on the mixture specimens. Finally, a visual or surface evaluation of moisture damage is performed. The extended exposure to moisture at high temperature and cyclic pressure helps in determining moisture damage susceptibility of the specimens from both adhesion and cohesion failures that can occur in the field.
SIGNIFICANCE AND USE
This test method provides an accelerated conditioning method for moisture exposure that can cause adhesive and cohesive strength failures in asphalt mixtures. The mixture response to moisture exposure is amplified by using high temperature and cyclic hydrostatic loading. The system described in the apparatus section is capable of operating at higher than normal temperatures and creating hydrostatic pore pressure within a compacted asphalt mixture to achieve an acceleration of the effects that a mixture would experience over time from traffic at normal temperatures and moisture conditions. The accelerated conditioning in this method is intended to simulate the stresses induced in a wet pavement by a passing vehicle tire.
4.2. The factors that influence the potential for moisture damage to occur in asphalt mix include aggregate mineralogy, mixture air voids, water, cyclic applied stress, and elevated temperature. This test method provides a method and apparatus that is capable of producing three of these factors: water, stress, and high temperature.
4.3. Specimens conditioned in this test method are evaluated using the tensile strength ratio, percentage of swell, visual inspection and surface evaluation of stripped aggregates.
5.4.1. The pressure chamber shall be capable of withstanding pressures of up to 485 kPa [70 psi].
5.4.2. The system shall be capable of producing and controlling cyclic pressures within the pressure chamber between 200 and 420 kPa [30 to 50 psi] with measurements accurate to within ±30 kPa [±4 psil.
5.4.3. The system shall be capable of heating the water and controlling the temperature between 30 and
70°C [86 to 158°F] with measurements accurate to within ±1°C [±2°F] for a predetermined period of time. The variation in temperature of the pressure chamber shall be within ±2°C [±4°F] of the temperature setpoint. Then, it shall automatically start the cyclic hydrostatic pressure conditioning.
5.4.4. The system shall be equipped with the ability to automatically purge and remove air from the pressure chamber, and then replace the accessible air void spaces with water.
5.4.5. The system shall have plates and spacers to prevent a specimen from resting on another specimen during conditioning.AASHTO TP 140-20 pdf download.