Abstract: A device for measuring density and moisture of a material includes a hollow roller rotatably mounted on a shaft for rolling movement on the surface of the material. A radioactive source and density and moisture detectors are supported below the shaft and adjacent to the inner surface of the roller at substantially a fixed distance from the surface of the material being measured as the roller is rolled. The detectors are coupled to a conventional counter and microprocessor circuitry which provide an output reading related to the density or moisture content of the material. The shaft may be mounted for tilting movement so that the roller may pitch in conformity to contours in the material surface.

Abstract: An in situ non destructive method employing a radiation device to rapidly determine the density of very thin top layers of material independently of the underlying base material comprising of the steps of: measuring the density D.sub.b of the base layer with an radiation measuring device, determining the thickness t of the top layer, measuring the density D.sub.g of the composite with the radiation measuring device, and determining the density of the top layer from the expression: ##EQU1##where k is a constant.

Abstract: A device for taking air gap backscatter radiation measurements at a pair of predetermined distances from the surface of a material is disclosed. The ratio of the first and second measurements are a function of the density of the material when one of the distances is sufficiently large that the measurement is dependent on the chemical content of the material but is independent of surface irregularities and density and when the second distance is greater than the average surface irregularity but sufficiently proximate to the material so that the measurement is independent of surface irregularities but is dependent on the density and the chemical content of the material. The device includes a housing slidably supported between a pair of end plates, a carrying handle for the device and a source within the housing. When the handle is in a first position, the source is disposed in a storage or "safe" position.