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Restrained shrinkage cracking: the role of shrinkage reducing admixtures and specimen geometry



Title: Restrained shrinkage cracking: the role of shrinkage reducing admixtures and specimen geometry
Author(s): W.J. Weiss, S.P. Shah
Paper category : conference
Book title: International RILEM Conference on Early Age Cracking in Cementitious Systems
Editor(s): K. Kovler and A. Bentur
Print-ISBN: 2-912143-29-2
e-ISBN: 2351580362
Publisher: RILEM Publications SARL
Publication year: 2003
Pages: 145 - 157
Total Pages: 13
Nb references: 12
Language: English


Abstract: Early-age cracking may occur in concrete elements if shrinkage is prevented by the surrounding structure. The risk of early-age shrinkage cracking in any given structure is influenced by many factors including the magnitude of shrinkage, rate of shrinkage, degree of stress relaxation, degree of structural restraint, and rate at which material properties develop. In addition to the aforementioned factors, this paper highlights the fact that shrinkage cracking is also influenced by geometry. This paper compares two series of experiments to better understand the role of specimen geometry. In the first series ring specimens of varying size were prepared to undergo the same rate of shrinkage and maximum strain development. Although the maximum residual tensile stress that developed was nearly identical for all geometries, the age at which cracking occurred varied with specimen thickness. In the second series of experiments the combined effect of moisture gradients and specimen geometry was investigated. In these experiments specimen thickness was varied while the surface area exposed to drying was maintained constant. The age of cracking was measured, as was the development of a moisture gradient. Again the influence of specimen size/geometry was apparent with smaller specimens cracking at an earlier age. This paper provides an explanation for this geometry dependence through the use of fracture mechanics concepts.


Online publication: 2010-06-02
Publication type : full_text
Public price (Euros): 0.00