The measurement of concrete density by back-scattered γ-radiation

The use of γ backscattering techniques in the quality control of concrete are considered. The performance of an instrument using this technique, the Ekco N 711B, is reported. It was found that quick and accurate measurements could be obtained which were independent of the material chemical constitution and that good correlation existed between ultrasonic pulse velocity, and the backscatter methods. The disadvantage of measuring backscatter from thin concrete members was overcome by using a steel backing plate that compensated for the back-scatter if the concrete depth was less than the semi-infinite depth. (U.K.)