A Prediction Method of Tensile Young's Modulus of Concrete at Early Age

Isamu Yoshitake,Andrew Scanlon,Farshad Rajabipour,Yoichi Mimura

doi:10.1155/2012/391214

Isamu Yoshitake, Andrew Scanlon + Show 2 more

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https://doi.org/10.1155/2012/391214

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Abstract

Knowledge of the tensile Young's modulus of concrete at early ages is important for estimating the risk of cracking due to restrained shrinkage and thermal contraction. However, most often, the tensile modulus is considered equal to the compressive modulus and is estimated empirically based on the measurements of compressive strength. To evaluate the validity of this approach, the tensile Young's moduli of 6 concrete and mortar mixtures are measured using a direct tension test. The results show that the tensile moduli are approximately 1.0–1.3-times larger than the compressive moduli within the material's first week of age. To enable a direct estimation of the tensile modulus of concrete, a simple three-phase composite model is developed based on random distributions of coarse aggregate, mortar, and air void phases. The model predictions show good agreement with experimental measurements of tensile modulus at early age.

Highlights

An accurate estimation of the Young’s modulus is important for proper structural design of concrete members, and ensuring their serviceability, such as controlling deflections and crack widths
The tensile modulus is assumed to be equal in value to the compressive modulus and is estimated using empirical correlations based on the compressive strength of concrete [1, 2]
The Architectural Institute of Japan (AIJ) [3] points out that employing the tensile modulus is more appropriate for estimation of the risk of earlyage cracking; the specification indicates that the compressive modulus may be used instead of the tensile modulus because investigations dealing with the tensile modulus are currently insufficient

Summary

Introduction

An accurate estimation of the Young’s modulus is important for proper structural design of concrete members, and ensuring their serviceability, such as controlling deflections and crack widths. The time-dependent development of the tensile Young’s modulus at early ages is needed for estimation of the tensile stresses that are generated due to restrained thermal and hygral shrinkage. These tensile stresses may lead to premature cracking of concrete members. The Architectural Institute of Japan (AIJ) [3] points out that employing the tensile modulus is more appropriate for estimation of the risk of earlyage cracking; the specification indicates that the compressive modulus may be used instead of the tensile modulus because investigations dealing with the tensile modulus are currently insufficient. Since the tensile behavior of concrete is more significantly affected by the presence of flaws (e.g., microcracks or large capillary pores common in early-age concrete), it is important to develop tools to predict or measure the tensile properties more accurately

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