The Dry Cracking of Cementitious Materials in the Eccentric Ring Test and the Concentric Ring Test

In order to reduce the randomness of the occurrence of cracks and shorten the long cracking time in the traditional concentric ring tests, the elliptical ring test, the square-eccentric ring test, and the eccentric ring test have been gradually developed. In this paper, we reported experiments on the eccentric ring test and concentric ring test that were carried out to compare the differences between the two methods. It is found that an increase in the water-cement ratio and the amount of aggregate will increase the cracking time. However, a more obvious cracking tendency of cement-based materials can be seen in the eccentric ring test. The correlation between humidity and strain was established by the use of the Kelvin equation and the Laplace equation so that the coupling analysis of humidity and strain during the drying process of cement-based materials could be determined. The experimental results show that the external surface humidity will decrease rapidly in the early stage of drying, while the interior areas of the cement-based materials decrease more slowly. The closer to the inner circle will decrease the humidity slowly.