The rheology of self-compacting concrete made with Belgian materials

Title: The rheology of self-compacting concrete made with Belgian materials
Author(s): Dimitri Feys, Ronny Verhoeven, Geert De Schutter
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
Print-ISBN: 2-35158-003-6
e-ISBN: 2351580028
Publisher: RILEM Publications SARL
Publication year: 2006
Nb references: 13
Language: English

Abstract: The rheology of fresh concrete and self compacting concrete (SCC) has been studied for several decades to better understand the flowing behaviour of these materials. This is especially important in cases the concrete is pumped into the formwork through pipes. Too stiff concretes, or concretes that segregate are not suitable for pumping operations. These concretes demand too high pressures or will cause blocking during pumping operations. Pumping SCC speeds up the casting process, because the concrete is more fluid and it does not need any compaction.
In literature, the rheological behaviour of fresh concrete and fresh SCC is mainly described by the Bingham model. For traditional concrete, this behaviour has been confirmed. However, tests with SCC, made with Belgian materials, indicate in most cases shear thickening behaviour. The Bingham model can not be applied because it causes negative yield stresses. The Herschel-Bulkley equation ( ) gives positive yield stresses, but it has some other problems. The dimension of the consistency factor “K” is dependent on the exponent “n”. As a result, this dimension is variable and “K” is inappropriate for physical interpretation. The Herschel-Bulkley curve is also forced mathematically to be horizontal for very low shear rates – in case of shear thickening – resulting in an overestimation of the yield stress.
The modified Bingham model ( ), i.e. the Bingham model extended with a quadratic term, correlates the data points as well as Herschel-Bulkley; has constant dimensions and gives a better fit for the yield stress. The degree of non-linearity, expressed by the parameter “n” in Herschel-Bulkley, can be examined with c/?. This model is also a Taylor development of the second order of the Herschel-Bulkley equation.
When examining the results from the rheometer tests, more shear thickening is observed when the slump flow increases. And when the w/p ratio decreases, c/? increases dramatically.

Keywords: Self compacting concrete, rheology, Bingham, modified Bingham, Herschel-Bulkley.

Online publication: 2006-08-02
Classification: 3.2 Theme 2: From Fresh to Hardened Concrete
Publication type : full_text
Public price (Euros): 0.00
doi: 10.1617/2351580028.060