Use of the Workability Box Concept

While self-consolidated concrete (SCC) has significantly penetrated the production of prestress precast concrete production, concerns still exist for overcoming the occurrence of mixture instability, which can result in unpredictable segregation. Such situations can frequently be linked to batch-to-batch variation in moisture content. In this paper, workability measurements in combination with stability indicating tests are used to determine a range of slump-flow and T50 concrete spread values that SCC mixtures should fall within to assure uniform consistency, and avoid segregation. This range of parameters is referred to as the Workability Box, Furthermore, the Workability Box concept can be used to demonstrate moisture tolerance as test mixtures can be repeatedly re-tempered with water to understand if the workability parameters (slump-flow and T50) of the SCC mixture shifts out of the zone of acceptable stability. The Workability Box has the capability to significantly improve quality control operations, and facilitate the successful production and placement of self-consolidating concrete.

---