Field evaluation of a direct transmission type nuclear moisture-density gauge

Results obtained by a nuclear moisture-density gauge were correlated to those obtained by a balloon type volume device and oven drying. The nuclear testing modes were direct transmission for wet density and backscatter for moisture. Comparison tests were made on active construction projects in each of 10 soil types and graded aggregate bases from 10 stone formations. The test results were analyzed statistically by regression, correlation coefficient, and t test (compression of the means). It was found that the manufacturer's wet density calibration curve provided acceptable results in all of the Missouri soil types and stone formations tested but that the manufacturer's water calibration curve frequently furnished unacceptable values for moisture content. Acceptable moisture content values were obtained with the nuclear gauge by use of a computed correction factor.