Determination of Water Content of Plastic Concrete Using a Microwave Oven.

摘要

Until now there has not been a simple test that could be performed in the field to accurately determine the water content of a plastic concrete mix. Oven or hot plate drying is unsatisfactory because the heat involved hastens cement hydration which makes a portion of the water non-evaporable. In our laboratory tests,drying by microwave oven on the defrost mode has been found to essentially overcome this problem. The time interval between introduction of the mixing water and start of the test did not affect the results up to the maximum time interval tested of one hour. The accuracy of the test is such that 95% of the time the true water content can be determined to within .06gallons/sack of cement. It takes about one hour to perform the test. Field trials on four construction projects were successfully accomplished which proved its practicality and value. (Color illustrations reproduced in black and white)