Early-age cracking has been found to occur in some concrete bridge decks, slabs, and pavements when the volumetric changes associated with drying, hydration, and temperature reduction are prevented. While free shrinkage tests can quantify length change, they may not always be sufficient for detecting materials that are prone to cracking since the potential for cracking is influenced by complex interactions of strength gain, stiffness development, creep, shrinkage, the degree of restraint, and toughness. The simplicity of the ring test enables it to be used as a comparative test to screen potential mixture designs. Based on the use of this test, AASHTO developed a provisional standard ring test which establishes specimen geometry, however the provisional standard does not provide an approach for quantifying stress development or indicating how close a specimen may be to failure. This paper describes a simple stress solution that can be used to quantify the results of the ring test. Issues related to ring and free shrinkage specimen geometries are discussed to improve the fundamental understanding of the information provided by the ring test. This paper describes how elastic stress and actual stress can be compared to provide a measure of the stress relaxation in a material. To better illustrate the microcracking and visible crack development process, acoustic emission testing was performed. These experiments indicated that specimens with a higher level of restraint exhibited more microcracking as a part of stress relaxation process.
|Book series||Transportation Research Record|
|Publication status||Published - 2003|