The measurement of the workability of dry concrete mixes

The paper describes tests on a number of dry mixes, using the Vebe and compacting factor principles, together with a third test based on the compacting factor test. The modified compacting factor test substitutes a period of vibration for the fall under gravity of the normal apparatus.

It is shown that the normal compacting factor test does not reflect the compaction properties of very dry mixes, as the amount of work done on the concrete is too small. The Vebe test is shown to be satisfactory and is recommendedfor more general use with dry mixes.