Determination of Fracture Energy of Early Age Concrete through a Uniaxial Tensile Test on an Un-Notched Specimen.

Dongya Ren,Lambert Houben

doi:10.3390/ma13030496

Dongya Ren, Lambert Houben

Open Access

https://doi.org/10.3390/ma13030496

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Abstract

Unlike the notched specimens for conventional concrete fracture tests, this paper introduces a deformation-controlled uniaxial tensile test on an un-notched specimen. The surface of the dog bone-shaped specimen is a second order parabolic curve, and the gradual change in the specimen shape does not lead to extreme stress concentrations. Another significant feature of the tension test set-up is that it is built with three hinges, to accommodate the alignment of the specimens. The specimen preparation, test conditions, and the tension test set-up are explained in detail. The fracture energy of the concrete is determined by the obtained complete softening curves. The fracture energy is found to increase with age, going towards a horizontal asymptote as concrete hardened in a tested age range of 1 day to 90 days. Moreover, the rate of development of the fracture energy was found to be higher when compared to tensile strength and stiffness.

Highlights

The tensile property of concrete at a very early age, in this case as early as the time of the initial setting of the concrete, is essential for the study of cracking control
There is very limited relevant information available, especially on the direct measurement of the fracture energy or the complete tensile softening curves for early age concrete. This is mainly due to practical problems, for instance, very early age concrete specimens with a low degree of hydration cannot yet support their own weight without applying any loads [1,2]
This paper introduces a deformation controlled uniaxial tensile test on un-notched specimens

Summary

Introduction

The tensile property of concrete at a very early age, in this case as early as the time of the initial setting of the concrete, is essential for the study of cracking control. There is very limited relevant information available, especially on the direct measurement of the fracture energy or the complete tensile softening curves for early age concrete. This is mainly due to practical problems, for instance, very early age concrete specimens with a low degree of hydration cannot yet support their own weight without applying any loads [1,2]. Cylindrical un-notched specimens introduce the problem that it is unknown where the crack will initiate, which means elaborate instrumentation is needed to control the test and measure the deformation response. Alternatives are so-called “dog-bone” or parabolic-shaped specimens, which localize the crack in the area with the smallest diameter

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