ASTM D7228-06a(2020)

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 temperature 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 installed 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 of temperature, 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.

1.1 This test method covers a means of predicting temperatures within the asphalt-bound layer(s) of a flexible pavement section.

1.2 Deflection testing commonly involves the measurement of pavement surface temperatures. This standard is based on temperature relationships developed as part of the Federal Highway Administration (FHWA) Long Term Pavement Performance (LTPP) Seasonal Monitoring Program.

1.3 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.