Analysis of Shrinkage Reducing Admixtures on Drying Shrinkage of Concrete

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Title: Analysis of Shrinkage Reducing Admixtures on Drying Shrinkage of Concrete

Author(s): C. Videla and C. Aguilar

Publication: Special Publication

Volume: 209

Issue:

Appears on pages(s): 319-346

Keywords: admixtures; concrete; drying shrinkage; extrapolation; mixture proportions; modulus of elasticity; portland pozzolan cement; shrinkage prediction models; shrinkage-reducing admixtures; statistical evaluation; updating; volume/surface ratio

Date: 9/26/2002

Abstract:
The objective of this research was to verify the feasibility of reducing the drying shrinkage of concrete made with portland pozzolan cement. Major variables included slump, shrinkage-reducing admixture brand, admixture dosages and specimen dimensions. Tests were carried out on 132 prism specimens and shrinkage strain8 were measured up to 360 days of drying. Also compressive strength, splitting strength and static modulus of elasticity were determined. Based on the results obtained, it was concluded that dl of the five brand admixtures evaluated reduce drying shrinkage. One Qf the experimental admix- tures exhibited the best behavior and reduced up,k, 45% of the average free shrinkage of concrete at 360 days of drying. Results were compared with drying strain predictions of ACI, CEB, B3, GL, Sakab and Sakata 2001 models. It was conduded that in general a l l the ana- lyzed shrinkage models do not adequately represent the observed shrinkage behavior of concretes made with portland pozzolan cement and shrinkage-reducing admixtures. Therefore, two prediction models to estimate drying shrinkage strains were developed based on the ACI drying-time function and Sakata’s ultimate shrinkage strain. One of these models is for use at a design level when no information about a particular shrinkage reducing admixture is known, and the other is applicable to concrete made with a particular admixture brand.