Evaluation of a Drop Table for Consolidating 6-Inch Diameter Cylindrical Concrete Test Specimens.

摘要

A drop-table apparatus was evaluated by the U.S. Army Engineer Waterways Experiment Station (WES) to determine if it should be standardized and used for consolidating 6-in.-diameter cylindrical specimens of fresh concrete by the U.S. Army Corps of Engineers. Test specimens were fabricated from six concrete mixtures of three different slumps using both the drop-table method and the rodding and vibration methods, currently authorized by CRD-C 10-78 (ASTM C 192-76). Density and compressive strength tests were conducted on the specimens after they had been continuously moist cured for selected periods of time. Standard deviations were calculated from the test data in order to compare the uniformity of consolidation of each fabrication procedure. The drop table consolidated the 6-in.-diameter concrete test specimens in a relatively uniform manner; however, the density and compressive strength test values were consistently lower than those obtained from the rodded and vibrated specimens. If it were decided to standardize procedures which produce drop-table test results comparable to those of current procedures, additional investigative work using alternative mold-filling techniques and varying height and number of drops would be required. (Author)