Nuclear Gauge Calibration and Testing Guidelines for Hawaii

The Hawaii Department of Transportation requires that ASTM/AASHTO standards be followed for acceptance of in-place density and moisture of soil and soil-aggregate determined by nuclear gauge or sand cone methods. The nuclear gauge technique is widely used by consultants, government agencies and researchers since it allows for a quick and cost-effective way to determine total wet density and water content. However, adherence to ASTM/AASHTO requirements, particularly with regard to standardization, calibration and verification procedures, has been reported to be problematic in Hawaii by consultants and testing firms, especially those operating on the neighbor islands. This is probably due in part to the unique mineralogy of some of the local volcanic soils. Also, the presence of coarse-grained soils and use of the nuclear gauge near trench walls and other inhomogeneities causes difficulty in trying to meet ASTM/AASHTO precision requirements for density and moisture content. Furthermore, precision guidelines in the AASHTO/ASTM standards do not cover some of the most common types of native soils, such as highly weathered residual and colluvium soils (ML and MH).