Time-Dependent Behavior of Shrinkage Strain for Early Age Concrete Affected by Temperature Variation

Yu Qin,Zhijian Yi,Di Wang,Weina Wang

doi:10.1155/2017/3627251

Abstract

Shrinkage has been proven to be an important property of early age concrete. The shrinkage strain leads to inherent engineering problems, such as cracking and loss of prestress. Atmospheric temperature is an important factor in shrinkage strain. However, current research does not provide much attention to the effect of atmospheric temperature on shrinkage of early age concrete. In this paper, a laboratory study was undertaken to present the time-dependent shrinkage of early age concrete under temperature variation. A newly developed Material Deformation Tester (MDT), which can simulate consecutive variation of atmospheric temperature, was used to collect the shrinkage strain of specimens and temperature data. A numerical model was established to describe the thermoelastic strain of a specimen. The results show that (1) there are several sharp shrinkages up to 600 μfor early age concrete in the first 3 days; (2) the absolute value of shrinkage strain is larger than thermal strain; and (3) the difference of shrinkage strain under temperature variation or constant temperature is up to 500 μ.

Highlights

The cracking of early age concrete is a major distress that affects structural integrity and sustainability
When concrete is restrained by itself or outside constraint, the strain generated by autogenous shrinkage and drying shrinkage can result in residual stress
Hobbs [5] investigated the effect of specimen geometry and curing period on the shrinkage of plain concrete specimens dried at 65% relative humidity (RH) and 20∘C

Summary

Introduction

The cracking of early age concrete is a major distress that affects structural integrity and sustainability. When concrete is restrained by itself or outside constraint, the strain generated by autogenous shrinkage and drying shrinkage can result in residual stress. When sufficient residual stresses develop (above approximately 50% of the strength), microcracking and damage start to occur in the interior of concrete. The characteristics of shrinkage of early age concrete have been highlighted in a number of investigations [1,2,3,4]. Hobbs [5] investigated the effect of specimen geometry and curing period on the shrinkage of plain concrete specimens dried at 65% RH and 20∘C. Lura et al [7] presented the results of an experimental study on the influence of curing temperature and type of cement on the autogenous deformations in early age concrete

Methods

Results

Conclusion