Integration approach of the Couette inverse problem of powder type self-compacting concrete in a wide-gap concentric cylinder rheometer

For powder type self-compacting concrete (SCC) mixes, commonly used in Belgium, a shear thickening (Herschel–Bulkley) flow behaviour of the fresh mixes is quite often observed. A longstanding problem in rheometry is the so-called “Couette inverse problem”, where one tries to derive the flow curve τ ( γ ˙ ) from the torque measurements T( N) in a (wide-gap) concentric cylinder (Couette) rheometer, with T the torque registered at the inner, stationary cylinder and N the rotational velocity of the outer, rotating, cylinder. In this paper, the Couette inverse problem is approached by means of the integration method in order to convert T( N) into τ ( γ ˙ ) for a wide-gap ( R o/ R i = 1.45) concentric cylinder rheometer. The approach consists in the decoupling of the flow resistance and the power-law flow behaviour after exceeding the flow resistance. The integration approach is validated by experimental verification with different powder type SCC mixtures. By means of illustration, the results of one limestone powder type SCC mixture with different superplasticizer contents are shown in this paper.