The role of specimen geometry and boundary conditions on stress development and cracking in the restrained ring test

Early-age cracking can be a significant problem in concrete pavements, floors, and bridge decks. Various test methods have been developed to assess the potential for early-age cracking, however due to the economy and simplicity of the ring test, it has become widely used. Although the ring test procedures employed by various authors are similar, they vary in terms of curing duration, specimen geometry, and boundary conditions. This paper describes an experimental study of restrained ring specimens tested using different geometries and boundary conditions. Specimen geometry was found to have a significant effect on the stress development and age of cracking in the restrained ring specimens. Specimens that shrink uniformly along the radius show the greatest variation in the age of cracking with thicker specimens cracking at a later age. Acoustic emission testing has been used to illustrate that specimen boundary condition substantially influence crack development and propagation in the restrained rings.