Using Fracture to Predict Restrained Shrinkage Cracking: The Importance of Specimen Geometry


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Title: Using Fracture to Predict Restrained Shrinkage Cracking: The Importance of Specimen Geometry

Author(s): W. J. Weiss, W. Yang, and S. P. Shah

Publication: Special Publication

Volume: 201


Appears on pages(s): 17-34

Keywords: cracking; early-age; geometry; restrained shrinkage; R-curve; shrinkage; testing

Date: 7/1/2001

Early-age cracking can occur in concrete if free shrinkage is prevented by the surrounding structure. This paper highlights recent findings to illustrate that shrinkage cracking is influenced by the geometry of the structure. A series of experimental results are presented from three different ring specimen geometries to illustrate that although these specimens had the same residual strain level (and similar residual stress), the age of cracking varied with specimen geometry. A second series of experiments was performed to illustrate that a geometry dependence also exists in specimens with moisture gradients. This paper describes how fracture mechanics concepts can explain this geometry dependent behavior under a uniform moisture distribution. Residual stress levels are computed, non-linear fracture mechanics failure criterion is applied to develop the time and geometry dependent tensile stress resistance curves, and the age of cracking is predicted. The theoretical simulations were found to compare reasonably with the experimental observations. A discussion is provided to illustrate how these considerations may be extended to the specimens with moisture gradients.