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Mitigation Strategies for Autogenous Shrinkage Cracking.


pdf icon Mitigation Strategies for Autogenous Shrinkage Cracking. (1943 K)
Bentz, D. P.; Jensen, O. M.

Cement and Concrete Research, Vol. 26, No. 6, 677-685, August 2004.

Keywords:

cracking (fracturing); autogenous shrinkage; concretes; mitigation; self-desiccation

Abstract:

As the use of high performance concrete has increased, problems with early-age cracking have become prominent. The reduction in w/c ratio, the incorporation of silica fume, and the increase in binder content of high performance concretes all contribute to this problem. In this paper, the fundamental parameters contributing to the autogenous shrinkage and resultant early-age cracking of concrete will be presented. Basic characteristics of the cement paste which contribute to or control the autogenous shrinkage response include the physicochemical properties of the pore solution (mainly its surface tension), the geometrical and topological properties of the pore network, the visco-elastic response of the developing solid framework, and the kinetics of the cementitious reactions. While the complexity of this phenomenon may hinder a quantitative interpretation of a specific cement-based system, it also offers a wide variety of possible solutions to the autogenous shrinkage and early-age cracking problem. Mitigation strategies which will be discussed in this paper include: the addition of shrinkage-reducing admixtures more commonly used to control drying shrinkage, control of the cement particle size distribution, modification of the mineralogical composition of the cement, the addition of saturated lightweight fine aggregates, the use of controlled permeability formwork, and the new concept of "water-entrained" concrete. As with any remedy, new problems may be created by the application of each of these strategies. But, with careful attention to detail in the field, it should be possible to avoid cracking due to autogenous shrinkage via some combination of the presented approaches.