The slump flow test is the most common field test and is currently in the process of being standardized by the American Section of the International Association for Testing Materials (ASTM). The slump flow test is simple; the slump cone is filled without consolidation and then lifted. The spread of the concrete after the cone is lifted is measured.

​

There are three important measurements to be taken: the total spread of the concrete (between 455 and 810mm), The T20(T50) measurement, and the resistance to segregation.

​

The T20(T50) measurement is the viscosity of the mix – or the time taken for the concrete to reach a spread diameter of 500mm. It varies between 2 and 10 seconds for SCC. A higher T20(T50) value means a higher viscosity mix, which is suitable for applications with congested reinforcement or deep sections. A lower T20(T50) value/viscosity is ideal for concrete traveling long horizontal distances with little to no obstructions.

​

The resistance to segregation is determined by the visual stability index (VSI). The notable features of the index are whether water bleed is observed at the leading edge of the spreading concrete, or if aggregates are piling at the center. VSI values range from 0 (highly stable) to 3 (unacceptable).