This report describes the results of an investigation made to assess the potentialities of nuclear moisture/density gauges for determining the in-situ density of cement-bound bases and sub-bases. The results of field trials showed that density measurements made with nuclear gauges used in the direct transmission mode were at least as accurate as densities determined by the sand replacement test and measurements made on cores cut from the hardened material. Furthermore the speed with which the results were obtained far exceeded those obtained by any other available method. A check of the accuracy and reproducibility of the results of nuclear measurements made on test blocks of known density confirmed that, for the majority of cases, density values recorded by the gauges were within 2 per cent of the actual value. The reproducibility of the results obtained by different operators and gauges was good. However, the work also suggested that there may be materials which give anomalous results because they do not follow the calibration curves for the gauges. Precautions therefore need to be taken in order to ensure that the material is behaving in the expected manner. (A)

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