Creep Properties of Fly-ash Cement Concrete for Thermal Stress Analysis

A study on protection against thermal cracks within mass concrete structures (VII)

Abstract

At present, the method which introduces creep of concrete is often used for thermal stress analysis within mass-concrete structures. Concrete is supposed to be a material that has different properties in compression or tension. In the case of analyzing thermal stress, therefore, the most exact analysis must be the method which applies separate creep in compression or tension, respectively. However, it is usual to carry out thermal stress analysis by using compressive creep only, because the computation to use both creep becomes rather complicated. Anyway, if the very accurate analysis of thermal stress is required, it is necessary to distinguish the tensile creep property from compressive creep property. Because of this idea, this paper describes the discrepancy between compressive creep and tensile creep of fly-ash cement concrete.
The test results are as follows.
i) The behavior of compressive creep is different from that of tensile creep; with instantaneous deformation, compression is greater than tension; with time-dependent deformation, tension is greater than compression.
ii) The rate of the flow method which defines a creep is influenced by early age. At early age, therefore, this method can not be used.
iii) Though the ideal method of thermal stress analysis within mass-concrete structures is the method to use separate creep in compression or tension, the method using only one-side creep has the capability to analyze the problem depending on the analyzing conditions.