Title:
Influence of Shrinkage-Reducing Admixtures on Development of Plastic Shrinkage Cracks
Author(s):
Pietro Lura, Brad Pease, Guy B. Mazzotta, Farshad Rajabipour, and Jason Weiss
Publication:
Materials Journal
Volume:
104
Issue:
2
Appears on pages(s):
187-194
Keywords:
cracking; durability; plastic shrinkage; settlement; shrinkage
DOI:
10.14359/18582
Date:
3/1/2007
Abstract:
The term plastic shrinkage cracking is generally used to describe cracks that form between the time when concrete is placed and the time when concrete sets. This paper discusses how the evaporation of water causes concave menisci to form on the surface of fresh concrete. These menisci cause both settlement of the concrete and tensile stress development in the surface of the concrete, which increase the potential for development of plastic shrinkage cracks. Specifically, this paper studies the development of plastic shrinkage cracks in mortars containing a commercially available shrinkage-reducing admixture (SRA). Mortars containing SRA show fewer and narrower plastic shrinkage cracks than plain mortars when exposed to the same environmental conditions. It is proposed that the lower surface tension of the pore fluid in the mortars containing SRA results in less evaporation, reduced settlement, reduced capillary tension, and lower crack-inducing stresses at the topmost layer of the mortar.