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Stress-strain measurement of fresh SCC at rest using a concrete viscometer



Author(s): P. Billberg
Paper category: Symposium
Book title: 3rd International RILEM Symposium on Rheology of Cement Suspensions such as Fresh Concrete
Editor(s): O.H. Wallevik, S. Kubens, S. Oesterheld
ISBN: 978-2-35158-091-2
e-ISBN: 978-2-35158-092-9
Pages: 265- 272
Total Pages: 8
Language: English


Abstract: 
The thixotropic property of self-compacting concrete (SCC) is said to have both a positive and a negative impact on production. The positive impact is related to form pressure, often shown to be lower than the hydrostatic pressure. The negative impact is related to the formation of casting folds, caused by too much elapsed time between casting of layers. Aside from the physical and reversible thixotropic process, an irreversible chemical reaction is also always present; starting from the moment the cement is intermixed with water. Thus, from an engineering point of view, the relevant property to focus on is structural build-up, in other words, the sum of physical and chemical phenomena occuring in SCC at rest. To capture the structural build-up, an approach is presented in which a concrete viscometer is used to create a stress-strain measurement of fresh SCC at rest. The peak stress value, the static yield stress, represents the total structure, and it is shown to increase linearly with time at rest. The Bingham (dynamic) yield stress development over time represents the irreversible part. However, the stress induced during the stress-strain measurement influences the rate of static yield stress increase with time, in that the material shows a strain-hardening behaviour.


Online publication: 2009
Publication Type: full_text
Public price (Euros): 0.00