Title: Effect of Gypsum Content and other Factors on Shrinkage of Concrete Prism

Author(s): Gerald Picket

Publication: Journal Proceedings

Volume: 44

Issue: 10

Appears on pages(s): 149-176

Keywords: none

DOI: 10.14359/8786

Date: 10/1/1947

Abstract:
The effects of gypsum content of cement and other factors on shrinkage and cracking tendency of concretes are investigated by methods described in a previous paper. An essential feature of the method is that prisms of the concretes are permitted to dry from only one side. It is found that there is in general an optimum gypsum content for each cement for minimum loss in weight, a different optimum for minimum shortening and still a different optimum for minimum warping. The data were too limited to indicate clearly whether or not there was also an optimum gypsum content for each cement for a maximum factor of safety against cracking. For the two cements of Type I used in this study the highest factors of safety were obtained with the highest gypsum contents used, indicating that the optimum was still higher. For the other cements there was no consistent indication that gypsum content had any effect on factor of safety. Specimens wet-cured 28 days shortened and warped less but developed higher shrinkage stresses than specimens wet-cured 7 days. There are indications that the rate of hydration during the first few hours has an effect on shrinkage during subsequent drying.