A rapid analysis machine (RAM) has been developed in Britain by the Cement and Concrete Association as a practical method of determining the cement content of fresh concrete. Water is pumped through the sample to separate the cement from the fresh concrete by elutriation. After passing through a 0.006-inch sieve to remove larger particles the slurry is treated with chemical agents, to make the cement particles cling together and settle in the conditioning vessel. When all the particles have settled the water level is lowered by means of a coarse and then a fine siphon, leaving a fixed volume of liquid plus cement in the constant-volume vessel. The vessel is removed from the machine and weighed, and the cement content of the concrete determined from a calibration graph.
Total time from loading the machine to reading off the answer from the graph is less than 10 minutes. Since the RAM is automatic and virtually self-cleaning it is not unusual to carry out four tests every hour during the working day. At present, the RAM is being used by contractors, testing laboratories, ready mixed concrete suppliers and government agencies. In most instances it is employed as a routine quality control method on large construction sites, but experience has shown that there is also a demand for a mobile RAM. In these cases the machine has been installed in a trailer, van or truck so that it can visit sites when critical concrete operations are taking place. An alternative solution to the small site problem is to take the concrete test sample (in a cold box) to a central laboratory for analysis.
In other instances the rapidity and accuracy of the machine have led to special applications such as the calibration of continuous mixers, or to its use as a means of determining the within-batch variation from stationary concrete mixers and truck mixers. It is also being used as a research tool by universities and technical institutions.