ASTM D7228-06a(R2020) pdf free download
ASTM D7228-06a(R2020) pdf free download.Standard Test Method for Prediction of Asphalt-Bound Pavement Layer Temperatures
4. Summary of Test Method
4.1 Input Data Elements: 4.1.1 IR Temperature—The exposed surface temperature of an asphalt pavement is measured, preferably with an infrared (IR) temperature sensing device that is properly calibrated. 4.1.2 Time of Day—The time of day the temperature mea- surement takes place is recorded. 4.1.3 1-Day Temperature—The average 1-day air tempera- ture of the previous complete 24-hour day is determined and recorded. 4.1.4 Pavement Depth—The depth at which an estimate of the asphalt layer temperature is required is specified. 4.2 The input data elements are entered into a regression formula that predicts the temperature within the asphalt pave- ment at depth.
5. Significance and Use
5.1 Analysis of deflection data from asphalt pavements almost always requires that the raw deflections or the analysis results from the load-deflection data be adjusted for the effects of pavement surface course temperature. Measuring the tem- perature at depth normally requires that a hole be drilled into the pavement, partially filled with fluid, and the temperature measured with a hand-held device. Alternatively, thermistors or other temperature instrumentation may be permanently in- stalled at various locations. 5.2 Current deflection testing equipment is often equipped with surface temperature sensing devices, for example an infrared thermometer that measures the surface temperature at every test location. To adequately adjust the deflection or deflection results for the effects oftemperature, the temperature at some depth must be known. 5.3 This test method provides a means of estimating the temperature at depth from the pavement surface temperature, the time of day, the previous day’s high and low air temperatures, and the desired depth where the temperature is to be estimated. Utilization of this method results in a significant savings in time over the conventional practice of manually drilling holes into the pavement, and it results in a significant increase in the volume of temperature data (one pavement temperature for each test point) and the ability to record temperature variations between test points.
6. Apparatus
6.1 Surface Temperature Measurement Device—The surface temperature measurement device can be an infrared (IR) thermometer mounted on a deflection device, a hand-held IR thermometer, or a surface contact thermometer. The tempera- ture measurement device should be calibrated according to the manufacturer’s recommendations.
7. Calculation
7.1 BELLS Method—The BELLS method for production testing (called BELLS3 in other publications) has been derived based on temperature measurements taken on pavement sur- faces that have been shaded for a short period (less than one minute) of time.N OTE 1—BELLS has been verified using the LTPP database at both mid-depth and third-depth temperature points. The regressions derived from the data at either depth were virtually identical; therefore, they were combined in deriving the BELLS equations. The asphalt layer thicknesses covered in the database were primarily between 50 mm and 300 mm; therefore temperature prediction depths within the AC layer should be limited to between 25 mm and 150 mm beneath the surface. Although this test method may be used for at-depth temperatures greater than 150 mm through extrapolation, the results have not been verified or calibrated to date. Since the equation’s boundary condition at depth = 0 is inconsistent with the input IR temperature value, the determination of an at-depth pavement temperature less than 25 mm is not recommended. N OTE 2—The database used to derive the BELLS equations consists primarily of data gathered during daylight hours between approximately 06:00 hrs and 18:00 hrs. Although the test method may be used outside of this time frame through extrapolation of the 18-hour sinusoidal relationships, the results have not been verified or calibrated to date.
