Mitigation Strategies for Autogenous Shrinkage Cracking.
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.
Building and Fire Research Laboratory
National Institute of Standards and Technology
Gaithersburg, MD 20899