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This test method covers the determination of the in-place density of bituminous mixtures by the attenuation of gamma radiation. There are two methods of measurement; where the source and detector remain on the surface (Backscatter Method) or where the source or detector is placed at a known depth while the source or detector remain on the surface (Direct Transmission Method). The density is determined by comparing the detected rate of gamma emissions with previously established calibration data. This test method is useful as a rapid, nondestructive way of determining the in-place density of bituminous mixtures. It is used for quality control and acceptance testing of compacted asphalt and can be used to establish the rolling effort and pattern necessary to achieve the required density.

 

The data entry and calculations for this test are performed on the Asphalt Nuclear Density form described in the next section. After the data and calculations have been performed the results are displayed in a test report as described in the reporting section below. The format of this report is controlled by the geotechnical template used for the test.

 

The methodology and calculations for this test adhere to "ASTM D2950-91 Standard Test Method for Density of Bituminous Concrete in Place by Nuclear Methods". For more detailed information on the methodology and calculations please review this standard.