Defining the stability criterion of a sphere suspended in a cement paste : a way to study the segregation risk in self-compacting concrete (SCC)

Title: Defining the stability criterion of a sphere suspended in a cement paste : a way to study the segregation risk in self-compacting concrete (SCC)
Author(s): S. Bethmont, L. D'Aloia Schwarzentruber, C. Stefani, R. Leroy
Paper category : conference
Book title: International RILEM Symposium on Self-Compacting Concrete
Editor(s): O. Wallevik and I. Nielsson
Print-ISBN: 2-912143-42-X
e-ISBN: 2912143713
Publisher: RILEM Publications SARL
Publication year: 2003
Pages: 94 - 105
Total Pages: 12
Nb references: 7
Language: English

Abstract: Designing Self-Compacting Concrete (SCC) usually consists in carrying out a series of experiments with the purpose to achieve a compromise between extreme fluidity and good resistance to segregation. However, the effects of concrete constituents on segregation are not always well understood and well controlled. More over, no test is actually satisfactory to estimate the segregation risk of SCC. The first part of this paper describes the analytical calculation of the stresses exerted by a rigid cylinder on an elastic medium. This medium can be also considered in a certain extend as a non-Newtonian fluid. Although the 3-Dimension problem (case of a sphere) cannot be solved analytically, a similar general expression can be given to the stability criterion and a solution can be found by carrying out experiments. Besides, this analytical calculation is completed by numerical simulation results. Hence, the stress fields induced by the displacement of both a cylinder and a sphere in an elastic medium can be compared. In the second part of this paper, several experimental results are reported. They deal with the influence of the rheological parameters of a cement paste (viscosity and shear yield stress) on the sinking of an aggregate of variable diameter, represented by a sphere. These experimental results are at the basis of the comparison and discussion of stability criteria found in the literature. The major aim of this study is a better understanding of the basic mechanisms at the origin of segregation. This will lead to the definition of the main characteristics required by a new test liable to make a proper estimation of the segregation risk.

Online publication: 2003-08-21
Publication type : abstract_only
Public price (Euros): 0.00