Putting Concrete to Sleep and Waking It Up with Chemical Admixtures

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Title: Putting Concrete to Sleep and Waking It Up with Chemical Admixtures

Author(s): L. Reiter; M. Palacios; T. Wangler; and R.J. Flatt

Publication: Special Publication

Volume: 302

Issue:

Appears on pages(s): 145-154

Keywords: admixtures; adsorption; cement hydration; set accelerators; set retarders; setting control; setting time

Date: 6/1/2015

Abstract:
The ability to control the setting of cement can be of use in various applications such as slip forming, oil well cements, or in normal applications due to variable conditions and time constraints. Typically cement setting is controlled via set retarders or set accelerators, but rarely are the two used in combination. The combination of the two, however, can lead to increased flexibility in construction methods. In this work, we present a system in which the dormant period of cement is extended with sucrose, and then drastically reduced by adding calcium hydroxide, a phase that preferentially adsorbs sucrose. We demonstrate that increasing doses of calcium hydroxide decrease the dormant period of sucrose-retarded cement, up to a complete cancellation of retardation, which is reached at the plateau of the sucrose-calcium hydroxide adsorption isotherm.