Tensile Properties of Early-Age Concrete

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Title: Tensile Properties of Early-Age Concrete

Author(s): Vinh T. N. Dao, Peter F. Dux, and Peter H. Morris

Publication: Materials Journal

Volume: 106

Issue: 6

Appears on pages(s): 483-492

Keywords: early-age concrete; fracture energy; plastic concrete; plastic cracking; tensile properties; tensile testing

Date: 11/1/2009

Abstract:
In this paper, the tensile properties of concrete at very early ages and their measurements are reviewed, and the need for further study is clearly highlighted. A newly developed apparatus and procedures for uniaxial direct tensile testing of concrete specimens at ages of 1.5 hours or more after mixing, together with the experimental results obtained, are reported. An improved knowledge of various important early-age properties is presented. The tensile strength, Young’s modulus, and fracture energy of early-age concrete are all found to increase very slowly during the first 3 hours or so, but significantly increase thereafter. Strong correlations are shown to exist between these three parameters, especially between tensile strength and fracture energy. The high values of fracture energy obtained strongly suggest that early-age cracking of concrete involves a significant zone of plastic straining or microcracking in the vicinity of the crack tip. Early-age concrete is also shown to be more ductile than mature concrete.