A radio-active method for measuring variations in density in concrete cores, cubes and beams

Abstract

Summary The paper describes an apparatus for measuring the variation of density along cores and beams of concrete. The variation of density is determined by measuring the change in the absorption of gamma radiation. The gamma rays emanate from a one millicurie source of caesium 137 and are detected by a scintillation counter. This is connected to a rate-meter and chart-recorder which continuously display the intensity of radiation transmitted as the sample traverses along its depth dimension through the gamma beam. The I'ariation in the intensity of the transmitted radiation is translated into density variations by a suitable calculation. Attention is drawn to the need to retain, for each type of specimen, the same source-sample-detector geometry, but it is shown that, with careful operation, variations in density may be measured with a standard deviation of about 1 lb/ft³. Although designedfor use with concrete specimens, the technique can be applied to any cohesive material.