Modification of the concrete rheometer to determine rheological parameters of self-consolidating concrete – vane device
Title: Modification of the concrete rheometer to determine rheological parameters of self-consolidating concrete – vane device
Author(s): Ammar Yahia, Kamal H. Khayat
Paper category : conference
Book title: 2nd International RILEM Symposium on Advances in Concrete through Science and Engineering
Editor(s): J. Marchand, B. Bissonnette, R. Gagné, M. Jolin and F. Paradis
Publisher: RILEM Publications SARL
Publication year: 2006
Nb references: 6
Abstract: Workability requirements for successful casting and proper performance of self-consolidating concrete (SCC) include high deformability and adequate stability. These characteristics depend on the yield stress and plastic viscosity of the concrete. SCC is designed to achieve low yield stress and moderate plastic viscosity in order to improve deformability and segregation resistance. The rheological parameters can be determined using concrete rheometers. Tattersal proposed the two-point workability rheometer and later the MK-III with an H impeller rotating in a planetary motion. Such a rheometer enables to describe the rheology of concrete in terms of flow resistance and torque viscosity. This device does not allow the calculation of the rheological parameters in terms of fundamental values due to the complex shear strain involved during testing. Ideally, rheometer test results should be comparable and independent of the device used, thus facilitating inter-laboratory comparisons and helping improve understanding of the SCC’s complex behaviour.
A study was undertaken to evaluate the possibility of modifying the MK-III rheometer by replacing the H impeller with a four-blade vane device rotating in a co-axial manner. Equations were also derived to convert the torque and rotational velocity values to fundamental parameters of shear stress and shear rate.
The use of the modified Tattersal rheometer was validated using various SCC mixtures. In this paper, test results obtained on SCC proportioned with 0.33 and 0.38 w/cm and different nominal size aggregates are reported. Highly viscous SCC mixtures made with relatively low w/cm are shown to fit best the Herschel-Bulkley model. The Herschel-Bulkley model does not lead to negative yield stress values sometimes encountered when using the linear Bingham model for SCC mixtures that exhibit high thixotropic characteristics.
Online publication: 2006-08-02
Classification: 3.2 Theme 2: From Fresh to Hardened Concrete
Publication type : full_text
Public price (Euros): 0.00