The amount of water used in a castable mix for preparing test specimens has a significant influence on subsequent test results. This test method is used primarily to determine and reproduce the consistency required for the optimum casting of refractory castables in the preparation of test specimens and to express that consistency quantitatively. The correct water content is one of the major factors that must be controlled to obtain uniform test specimens. Excess water can reduce strength, increase volume shrinkage, and promote segregation of the castable ingredients. Insufficient water can produce "honeycombs" (air voids) in the castable because of poor consolidation during placement and prevent complete hydration of cement.

The flow table (see sketches in Specification C 230/C 230M) has been found to be an excellent tool for measuring the consistency of a castable and should be used in cases where a numerical result is required. Since castables differ somewhat in their "body" or plasticity, it has been found that a good casting range, expressed numerically, might vary from castable to castable. While one material may cast well between 40 and 60 % flow, another material may need to be in the 60 to 80 % flow range to properly flow. Because of this, it has been found that no arbitrary optimum range can be stated for all castables. The flow table then becomes a tool for measuring the flow and not determining it. It can allow the operator to follow the manufacturer'recommendations or to reproduce the consistency of a particular castable between laboratories.

Total time of wet mixing must be closely controlled to obtain reproducible results.

This test method is not intended to be used to determine the proper water content for gunning applications, although it may provide information of value for interpretation by a skilled operator.