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Edition:Final Report
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Abstract:Standard portable nuclear moisture-density gauges are very accurate and easy to operate for determining density and moisture content of soils as well as other construction materials. Unfortunately, the size of the radioactive sources used in the standard nuclear gauges are such that they are regulated by the Nuclear Regulatory Commission and in Iowa, the Department of Public Health. Recently, a new portable gauge was developed by Troxler called the EGauge that measures wet density. The EGauge uses the technology of a nuclear gauge, but it has a low radioactive source and is exempt from licensing. The non-regulated EGauge is paired with the use of a moisture probe to measure moisture content. The Iowa DOT currently has ten portable nuclear gauges that are used for quality assurance (QA) testing on embankment construction with moisture and density control or moisture control only. If the new EGauge is sufficiently accurate, they could be made much more accessible to the construction and materials staff monitoring contractors’ quality control (QC) testing. Based on the licensing exemption, there could be a quantifiable savings with the new gauges and more importantly a reduced risk of injury or death from radiation exposure. Additionally, if the new type of gauge is allowed, there would be a savings and reduced risk for contractors performing QC testing. The study used comparative tests between the EGauge and the standard nuclear gauge on grading projects. Samples were collected to compare wet density, dry density, and moisture content using the different gauges. A recommendation was made to allow the use of the non-regulated nuclear gauge for wet density only and Materials IM 204, Appendix A was revised to allow for low activity nuclear gauges, such as the Troxler EGauge, as an acceptable test method for wet density. Based on the inconsistency in differences (i.e. moisture offset) for the same material and the low R-square value comparing the EGauge moisture probe to oven-dried moisture content, it was not recommended to use the EGauge moisture probe.
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