DEVELOPMENT OF AN ENERGY-BASED APPROACH TO WORKABILITY CHARACTERIZATION

Although the slump test has been widely used for decades throughout the world to measure concrete consistency, a better test method is needed for determining the workability of low-slump, dry-consistency concrete mixtures. Such a test method should measure fundamental flow properties under vibration. The vibrating slope apparatus, which was originally developed for the Federal Highway Administration (FHWA) for measuring the workability of low-slum concrete, was found to be a highly indirect and cumbersome method for measuring concrete viscosity under vibration. A modified energy-based approach, the International Center for Aggregates Research (ICAR) flow energy method, measures the minimum vibration energy to initiate concrete flow and the rate of flow at a given energy. Preliminary testing has shown that the ICAR flow energy method, which was developed in cooperation with FHWA, is capable of successfully detecting changes in the workability of dry-consistency concretes and is more sensitive than the slump tests in measuring such mixtures.