A generalized approach for the determination of yield stress by slump and slump flow

The slump test (ASTM C-143) is the most common method for assessing the flow properties of fresh concrete. Although slump provides a qualitative measure of workability, the relationship between slump and more quantitative rheological parameters is not fully understood. In this study, a dimensionless model relating slump to yield stress is further developed and generalized as a function of cone geometry. Yield stress measurements of cement paste are performed using a vane technique and compared with slump measurements using cylindrical and conical geometries. The cylindrical slump model is in excellent agreement with the experimental yield stress data obtained using the vane method. The data for the conical slump measurements fit the cylindrical model at low yield stress values, but the results deviate as the yield stress of the paste increases. Most of the other slump models available in the literature, including finite element models, predict the same yield stress for a given slump when converted to dimensionless form. The results suggest that a fundamental relationship exists between yield stress and slump that is independent of the material under investigation and largely independent of cone geometry.