Cracking Sensitivity of Normal- and High-Strength Concretes

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Title: Cracking Sensitivity of Normal- and High-Strength Concretes

Author(s): Konstantin Kovler and Arnon Bentur

Publication: Materials Journal

Volume: 106

Issue: 6

Appears on pages(s): 537-542

Keywords: cracking; curing; ring test; shrinkage; shrinkage-reducing admixture; tensile stress

Date: 11/1/2009

Abstract:
The influence of technological parameters on the cracking performance of concretes with regards to mixture design, curing, and use of admixtures in normal-strength concretes (NSC) and high-strength concretes (HSC) was investigated. It is concluded that shrinkage and cracking sensitivity are largely independent of the water-cement ratio (w/c) and cement content in NSC. Yet, the internal shrinkage-induced stresses are higher in the lower w/c concrete, but because its strength is also higher, cracking sensitivity is not different than that of a higher w/c concrete. HSC is much more sensitive to cracking than NSC but this sensitivity can be mitigated by either sealed curing or incorporation of shrinkage-reducing admixtures (SRA). Combination of the two results in concretes with very little buildup of internal stresses upon drying. The integrated criterion for cracking sensitivity, based on combining the criteria of time to cracking and stress rate, was shown to be more reliable for the classification than the individual ones.