Quantifying the influence of specimen geometry on the results of the restrained ring test

Over the last decade, the restrained ring test has frequently been used to assess the cracking susceptibility of a concrete mixture when it is restrained from shrinking freely. Despite the frequent use of the ring test, limited analysis has been performed to understand how the specimen geometry influences the results of the test. This paper discusses the influence of specimen geometry on the results of the ring test considering three conditions: (1) uniform shrinkage of the concrete ring, (2) shrinkage caused by drying from the top and bottom surfaces of the concrete ring, and (3) shrinkage caused by drying from the outer circumference of the concrete ring. The role of moisture gradients, thickness of the concrete and the restraining (i.e., steel) rings, and the stiffness of concrete are considered in a series of numerical simulations. Results from these simulations can enable better selection of test specimen geometries and interpretation of the results from the ring test. Analytical expressions are provided to use for determining the geometry of the ring specimen that better simulates specific field conditions while providing the most useful information from the test.