Title: Properties of an Expansive Cement for Chemical Prestressing
Author(s): Alexander Klein, Tsevi Karby, and Milos Polivka
Publication: Journal Proceedings
Appears on pages(s): 59-62
Expansion characteristics and compressive strengths were determined for concretes containing expansive cement to evaluate the factors relating to control of the expansive reaction. The expansive cement consists of a portland cement component and a calcium-sulfoaluminate anhydrite component. The factors influencing the magnitude and rate of the expansive reaction include: chemical composition of the components, fineness of the sulfoaluminate component, proportions of the two components in the total cementing material, ratio of water to total cementing material, rich-ness of mix, conditions of curing, and degree of restraint. In this investigation, the chemical composition of the components and the fineness of the sulfoaluminate component were kept essentially constant, and other factors influencing magnitude and rate of expansion were varied. For this study, restraint in all cases was provided by external steel mechanisms, in some cases restraint being uniaxial, and in other cases biaxial. In the absence of restraint, concrete exhibited free expansions up to 6 percent or more. The properties of the concretes reported herein indicate that certain of the expansive cements tested are suitable for structural work and can effectively be employed in the manufacture of chemically prestressed members under conditions of external restraint. It was established that with proper mix proportioning and curing, with compositions, proportions, and fineness of components fixed, it is possible to produce concretes having desired predetermined char- acteristics within a practical range.