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Technical Resource:
Robustness
of SCC
Introduction
Self-consolidating concrete is designed to meet specific applications requiring high deformability, high flowability, and high passing ability. The maximum flowability is governed by the application, and since flowability is controlled by the composition of the mix, observations show that the rheological properties of SCC vary in a wide range, so does its robustness. A recent overview on SCC types, properties, and test methods, are given by Bonen and Shah[i], and Khayat and his
In a narrow sense, the term ‘robustness’ might be synonymous to stability, as the latter term refers to the ability of SCC to resist changes, i.e., segregation during transport and placement (dynamic stability) and post placement (static stability). In a broader and more practical sense, the term robustness that is adopted here describes robustness as the ability of a given mixture to maintain its fresh properties and uniformity during processing, casting, and due to some small changes to the composition of the mixture due to some small changes in the mixture’s ingredients contents. The term uniformity might be divided into two subcategories; (a) resistance to segregation because of the inherent composition of the mix, and (b) resistance to segregation because of processing that affects the rheological properties.
Indeed, some properties, such as loss of fluidity and compatibility are frequently encountered with regular concretes. However, SCC might be more susceptible than ordinary concrete because: (a) the mix design is more complex as it contains more ingredients that each of them might affect the rheological properties differently, (b) SCC it is likely to be more thixotropic than ordinary concrete, and (c) the requirements from SCC are by far more demanding, thus what might be acceptable for ordinary concrete, might not meet SCC requirements.
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[i] Bonen, D. and Shah, S.P., “Fresh and hardened properties of self-consolidating concrete,” Progress in Structural Engin. Mater. J.,Vol 7(1) 14-26, 2005.
[ii] Khayat, K.H., “Workability, Testing and Performance of Self-Consolidating Concrete,” ACI Materials Jr., Vol 96(3) 346-353, 1999.
[iii] Khayat, K.H., Hu, C. and Monty, H.,” Stability of SCC, advantages and potential applications,” in RILEM International Confer. on Self-Compacting Concrete, Stockholm, Sep. 1999.
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