Research is reported that attempted to establish the applicability, bias, and validity of methods and procedures to rapidly determine the water or cement or both of freshly mixed concrete. The test procedures investigated were as follows: (1) U.S. Army Construction Engineering Research Laboratory Concrete Quality Monitor; (2) Federal Highway Administration Nuclear Cement Content Gage; (3) Rapid Analysis Machine; (4) X-ray Emission Spectrometer; (5) modified U.S. Army Engineer Waterways Experiment Station centrifuge; (6) hot plate; and (7) microwave oven. Sixty-one different concrete mixtures containing different amounts of concrete materials were used to evaluate the test procedures. It was found that no one test could rapidly and without bias determine the water or cement content of all the portland cement concrete mixtures. The ingredients of portland cement concrete can significantly affect the rapidity and accuracy of a test procedure. Also, if a procedure is to be used in a quality assurance program, the type or types of concretes proposed will determine which procedure or combination of procedures should be used. None of the procedures can qualitatively detect the unexpected presence of ground granulated iron blast-furnace slag or fly ash.
Abstract