Temperature a vital role in predicting pavement characteristics.

Temperature of pavement
is one of the most influencing factor in both Asphalt pavements and rigid
pavements. The stiffness, or modulus, of AC is
extremely sensitive to temperature. Deflection testing is used to evaluate
variety of pavement characteristics, including axle or vehicle load capacity,
structural life, and uniformity. Deflection test results are dependent on
seasonal variation. To get correct deflection results it should be adjusted
according to temperature values. Temperature and moisture affect
deflection response of both flexible pavements (asphaltic concrete) and rigid
pavements (Portland Cement Concrete). The stiffness (rigidity) of asphalt
concrete (AC) is very sensitive to temperature changes occurring over both long
term (seasonal) and short term (hourly) periods. As the temperature of the
pavement increases, the magnitude of deflection from a given impulse load will
increase if all other factors remain the same. Therefore, deflections measured
on a hot summer day will be larger than the deflections measured during a
cooler period. Also, changes in temperature with depth (vertical temperature
gradients) influence stresses in the AC layer. The influence of vertical
temperature gradients becomes more pronounced as the thickness of the AC
increases. 5 Therefore, Temperature has a vital role
in predicting pavement characteristics. The temperature values for the state of
TEXAS can reach up to 110 F. These temperature values have profound effects on
the test that are done on test sections. The report uses several temperature
values to predict temperature at various depths. The surface temperature of the
pavement is measured during the FWD testing using IR sensors. The
FWD computer automatically records the information. Associated information
includes the site number, date of test, and time of test. Air temperature is
another important parameter that contributes to the temperature at various
depth of the pavement. Several instruments are used to record temperature.
Thermistors, a type of resistor whose resistance is dependent on temperature is
used at various depths to record temperatures. Manual in-depth pavement
temperature measurements from holes drilled at each end of test section to
specified depth in the pavement. Temperatures are measured at two locations,
generally about a meter before and after the test section. The in-depth
temperature is measured manually with a hand-held digital thermometer. The
temperatures are measured about every half hour and hand recorded on a form,
along with information about the station and site number, time and date of the
measurement, depth of the hole. 2 Linear interpolation is a
technique that is used to find temperature at various depths as temperature
follows linear trend and the interpolated values are compared with the manually
recorded temperatures. The temperature data are obtained from LTPP (Long Term
Pavement Performance) database and Seasonal Monitoring Program (SMP) sections.


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