Shrinkage Characteristics of Alkali-Activated Slag Cements
Publication: Journal of Materials in Civil Engineering
Volume 27, Issue 7
Abstract
Recent interest in creating green construction materials has sparked the development of portland cement–free binders. Alkali-activated slag (AAS) concrete has a low embodied energy and comparable or superior strengths to ordinary portland cement (OPC) concrete. However, one factor limiting AAS usage is its durability performance, specifically its susceptibility to shrinkage. Before declaring AAS a marketable product, the mechanisms behind its volumetric instability need to be understood. This paper presents a preliminary study of the shrinkage deformations of various AAS mixtures, wherein four unique AAS mortars were designed and tested for autogenous, chemical, and drying shrinkage; time of setting; and compressive strength. All results were compared to those obtained for a control OPC mortar. Alkali-activated slag mixtures with comparable strength to OPC show a higher autogenous and drying shrinkage. A lower elastic stiffness, higher degree of saturation, and potentially higher chemical shrinkage contribute to the high autogenous shrinkage of AAS. A lower elastic stiffness also leads to a large drying shrinkage, although other mechanisms, such as reduced pore size and carbonation shrinkage, are likely to also contribute to the high drying shrinkage measured for AAS.
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Acknowledgments
The authors gratefully acknowledge the financial support from the National Science Foundation (NSF) under Award CMMI No. 1265789. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the NSF. The authors are also appreciative of the invaluable assistance of J. Wright and D. Fura. All tests were performed at the Civil Infrastructure Testing and Evaluation Laboratory (CITEL) and the Materials Research Institute (MRI) of Pennsylvania State University, University Park, Pennsylvania.
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Published In
Journal of Materials in Civil Engineering
Volume 27 • Issue 7 • July 2015
Copyright
© 2014 American Society of Civil Engineers.
History
Received: Sep 2, 2013
Accepted: Feb 5, 2014
Published online: Jul 11, 2014
Discussion open until: Dec 11, 2014
Published in print: Jul 1, 2015
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