Experimental Validation of Relaxation Prediction Models in Concrete
Publication: Journal of Materials in Civil Engineering
Volume 30, Issue 11
Abstract
Concrete undergoing volumetric changes is likely to be met with sustained restraint. This restraint leads to stresses which are reduced by tensile relaxation, in turn enabling the mitigation of cracks. Although creep and relaxation are said to be related, creep is well understood, while relaxation is not. In addition, relaxation is predicted from creep values because of the difficulty involved in performing relaxation experiments. This study validates approximate relaxation prediction models by comparing predicted values with experimental results. Two related methods are used: the effective modulus method and the age-adjusted effective modulus method (AAEM). Results indicate that using approximate relaxation models to predict early-age relaxation is valid. The accuracy of prediction increases as ultimate relaxation is reached, i.e., after 72 h for both the effective modulus method and the AAEM. No improvements in predictions are observed when the AAEM is used. The nature of load application does not seem to influence predictions.
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Acknowledgments
Financial and logistical support for this study was provided by the University of Cape Town’s Department Of Civil Engineering under the Concrete Materials and Structural Integrity Research Unit (CoMSIRU). Professor Hans Beushausen and Professor Pilate Moyo of the Department Of Civil Engineering of the University of Cape Town provided scientific and technical input in the design of this study. Dr Masuzyo Chilwesa of the School of Civil and Environmental Engineering, University of South Wales, Sydney, Australia proofread the initial manuscript.
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Published In
Journal of Materials in Civil Engineering
Volume 30 • Issue 11 • November 2018
Copyright
©2018 American Society of Civil Engineers.
History
Received: Aug 29, 2017
Accepted: May 24, 2018
Published online: Sep 4, 2018
Published in print: Nov 1, 2018
Discussion open until: Feb 4, 2019
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