4.1 The test method described is useful as a rapid, nondestructive technique for determining the in-place density of compacted asphalt mixtures.

4.2 With proper calibration and confirmation testing, the test method is suitable for quality control and acceptance testing of compacted asphalt mixtures.

4.3 The test method can be used to establish the proper rolling effort and pattern to achieve the required density.

4.4 The nondestructive nature of the test allows repetitive measurements to be made at a single test location between roller passes and to monitor changes in density.

4.5 The density results obtained by this test method are relative. Correlation with other test methods such as D1188/D1188M, D2726/D2726M, or D6752/D6752M is required to convert the results obtained using this method to actual density. It is recommended that at least seven core densities and seven nuclear densities be used to establish a conversion factor. A new factor must be established at any time a change is made in the paving mixture or in the construction process.

Note 1: The quality of the results produced by this standard are dependent on the competence of the personnel performing the procedure and the capability, calibration, and maintenance of the equipment used. Agencies that meet the criteria of Specification D3666 are generally considered capable of competent and objective testing, sampling, inspection, etc. Users of this standard are cautioned that compliance with Specification D3666 alone does not completely ensure reliable results. Reliable results depend on many factors; following the suggestions of Specification D3666 or some similar acceptable guideline provides a means of evaluating and controlling some of those factors.

1.1 This test method describes a test procedure for determining the density of asphalt mixtures by the attenuation of gamma radiation, where the source and detector(s) remain on the surface (backscatter method) or the source or detector is placed at a known depth up to 300 mm [12 in.] while the detector or source remains on the surface (direct transmission method).

1.2 The density, in mass per unit volume of the material under test, is determined by comparing the detected rate of gamma emissions with previously established calibration data.

1.3 The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.

1.4 All observed and calculated values shall conform to the guide for significant digits and rounding established in Practice D6026.

1.5 For limitations, see Section 5 on Interferences.

1.6 The text of this standard references notes and footnotes which provide explanatory material. These notes and footnotes (excluding those in tables and figures) shall not be considered as requirements of the standard. It is the recommendation of Committee D04 that the following note be added to the end of the Significance and Use section of all applicable standards. Applicable standards are those in which measurement or calibration are made, sample are procured, or products are selected. The subcommittee shall determine the appropriateness of adding the note throughout the consensus process.

1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific warning statements, see Section 7.

1.8 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.