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Relaxation characteristics of cement mortar subjected to tensile strain

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Abstract

Tensile relaxation characteristics are important for the crack resistance of concrete members subjected to restrained contraction, for example bonded overlays and patch repairs. In the experimental research discussed in this paper, relaxation characteristics were measured for mortar specimens subjected to constant strain which corresponded to stresses close to the tensile strength of the mortar. Relaxation was found to relieve a considerable portion of tensile stresses. Ultimate relaxation values ranged from 20 to 45%, depending on w/c ratio and specimen age. As expected, a decrease in specimen age and an increase in w/c ratio resulted in increasing relaxation values. The rate of stress decay was found to be rapid, with approximately 80% of the ultimate relaxation occurring in the first 12 h after loading. A basic equation for the prediction of time development of relaxation is proposed and future research needs are discussed.

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Authors and Affiliations

  1. Department of Civil Engineering, University of Cape Town, Rondebosch, Western Cape, South Africa

    H. Beushausen, C. Masuku & P. Moyo

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  1. H. Beushausen
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  2. C. Masuku
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  3. P. Moyo
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Correspondence to H. Beushausen.

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Beushausen, H., Masuku, C. & Moyo, P. Relaxation characteristics of cement mortar subjected to tensile strain. Mater Struct 45, 1181–1188 (2012). https://doi.org/10.1617/s11527-012-9825-2

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  • DOI: https://doi.org/10.1617/s11527-012-9825-2

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