Transitional Thermal Creep of Early Age Concrete

Anders Boe Hauggaard-Nielsen, Lars Damkilde, Per Freiesleben Hansen

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    Abstract

    Couplings between creep of hardened concrete and temperature/water effects are well-known. Both the level and the gradients in time of temperature or water content influence the creep properties. In early age concrete the internal drying and the heat development due to hydration increase the effect of these couplings. The purpose of this work is to set up a mathematical model for creep of concrete which includes the transitional thermal effect. The model govern both early age concrete and hardened concrete. The development of the material properties in the model are assumed to depend on the hydration process and the thermal activation of the water in the microstructure. The thermal activation is assumed to be governed by the Arrhenius principle and the activation energy of the viscosity of water is found applicable in the analysis of experimental data. Changes in temperature create an imbalance in the microstructure termed the microprestresses, which reduces the stiffness of the concrete and increase the creep rate. The aging material is modelled in an incremental way reflecting the hydration process in which new layers of cement gel solidifies in a stress free state and add stiffness to the material. Analysis of experimental results for creep of early age and hardened concrete either at different constant temperature levels or for varuing temperature histories illustrate the model.
    Original languageEnglish
    JournalJournal of Engineering Mechanics
    Volume125
    Issue number4
    Pages (from-to)458-465
    ISSN0733-9399
    Publication statusPublished - 1999

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