Effect of Shrinkage on Thermal Restrained Strain in Mass Concrete

Abstract

The aim of this study is to simulate restrained strain of mass concrete at early age due to combined thermal effect and shrinkages. Firstly, restrained strain caused by differential thermal expansion as well as restrained strains caused by shrinkages are separately computed. Thermal properties such as specific heat, thermal conductivity and thermal expansion coefficient of concrete are estimated by the authors’ mathematical models.  The previously proposed adiabatic temperature rise model is used to calculate heat of hydration. Heat of hydration obtained from the modified adiabatic temperature rise model and thermal properties derived from our proposed models are used as the input in a commercialized three-dimensional finite element program to calculate semi-adiabatic temperature and restrained strain. The restrained strains caused by shrinkages are computed based on our existing mathematical models for estimating free shrinkages. Both autogenous and drying shrinkages are considered. The total restrained strain is subsequently computed by the supercomposition concept. It is found that autogenous shrinkage reduces the thermal cracking risk at early age during the insulation curing period, while after removal of insulation curing material drying shrinkage increases the risk of cracking.

Keywords: mass concrete; semi-adiabatic temperature rise; thermal cracking; drying shrinkage; restrained strain