Analysis of fresh concrete: repeatability and reproducibility by the rapid analysis machine

This Report describes work carried out on a motorway site to estimate the precision, ie repeatability and reproducibility, of the determination of the cement content of fresh concrete when using the Rapid Analysis Machine (RAM). The repeatability was found to be 20 kg/cu m and the reproducibility 36 kg/cu m. A comparison of the precision obtained when analysing laboratory-mixed non-air-entrained and air-entrained concretes showed that the precision remained much the same, provided a de-air-entraining agent was added to, and thoroughly mixed with, the air-entrained sample prior to analysis.(A)