Title:
Does Concrete Shrink or Does it Swell?
Author(s):
Pierre-claude Aitcin
Publication:
Concrete International
Volume:
21
Issue:
12
Appears on pages(s):
77-80
Keywords:
autogenous shrinkage; curing; drying shrinkage; durability; high-performance concretes; setting
DOI:
Date:
12/1/1999
Abstract:
The importance of autogenous shrinkage is presently underestimated, especially in the case of high-performance concrete having a low water-cement or water-binder ratio. In such concrete, autogenous shrinkage is not negligible and its development can increase the risk of severe cracking. But, if hydration is occurring in the presence of an external source water, self-desiccation and autogenous shrinkage do not develop or are drastically diminished, depending on how this external water can penetrate the hydrating cement paste. It is not as well known that when concrete undergoes early water curing, it swells slightly, whatever its water-cement or water-binder ratio. Therefore, with early water curing, not only self-desiccation and autogenous shrinkage are absent but, on the contrary, concrete swells slightly. Concrete must be water cured not only to favor the hydration of cement, but also to limit the volumetric changes due to autogenous shrinkage. To achieve this, water curing must start before the initial setting time.