OVERVIEW OF RING TEST TO ASSESS CRACKING RESISTANCE OF EARLY-AGE CONCRETE

The early-age concrete under the condition of restrained shrinkage is easy to crack, which would affect safety and durability of the structure, as well as the applicability. So it is very important to provide a simple and effective method to assess the crack resistance of the early-age concrete. In view of providing certain rigidity and the convenience of laboratory constraints, the restrained shrinkage ring test is widely used to evaluate the crack resistance of the concrete under restrained shrinkage conditions. This paper discusses the development of the restrained shrinkage ring test, the failure mechanism and the impact of three factors. The restrained shrinkage ring test is recommended as a standard test method by the American Association of State Highway and Transportation Officials (AASHTO) and the American Society for Testing and Materials (ASTM), and the test is conducted for different purposes, including the failure mechanism based on the maximum tensile stress fracture mechanics theory and the fracture energy to predict the concrete cracking. The annular test specimen geometry, the boundary conditions, the performance of the concrete materials and the pre-crack are considered as influencing factors. A test method of elliptical ring is adopted, which can effectively assess the crack resistance of the concrete under conditions of high degree of restraint.