I am interested in obtaining an instrument with which I could quickly and easily read the amount of moisture in a concrete slab. Would you be aware of any firm that manufactures such an instrument?
One type of instrument consists of a sensor which is embedded in a well in the concrete and electrically connected to an indicator or recorder. Such equipment is available from American Instrument Company, 8030 Georgia Avenue, Silver Spring, Maryland 20910. Another type of gage consists of a color-indicating test button which may be impressed onto the surface of fresh concrete and then covered with a curing membrane or curing compound. The gage, described in Concrete Construction, July 1971, page 279, is manufactured by Humidial Cororation, Box 464, Colton, California 92324. The Corps of Engineers has evaluated a number of kinds of humidity-measuring instruments. The results were published in February 1976 in the 69page Technical Report C-76-1, An Evaluation of Selected Instruments Used to Measure the Moisture Content of Hardened Concrete, by Edward F. O'Neil and James E. McDonald. It is available from the Concrete Laboratory, U.S. Army Engineer Waterways Experiment Station, Box 631, Vicksburg, Mississippi 39180.