On concrete restrained eccentric ring and squared eccentric ring shrinkage test methods

• Two improvements based on concrete restrained shrinkage ring test.
• The inner ring in mold geometry is now placed eccentrically.
• Stress concentration is induced by the eccentricity in mold geometry.
• Cracking location is predictable.
• Cracking time is noticeably shortened.

In the conventional restrained ring test method (RRTM) for evaluating restrained concrete shrinkage, the specimen geometry is a concentric ring, which causes cracking initiation anywhere in the ring randomly and it is inconvenient to observe. Aiming at improving the identification of cracking location, this article presents two improvements based on RRTM, namely the restrained eccentric ring test method (RERTM) and the restrained squared eccentric ring test method (RSERTM), in which the specimen geometry is a non-concentric ring for the former and a square with a non-concentric hole inside for the latter. In other words, in comparison with RRTM, the specimen geometry in RERTM and RSERTM now is featured with the inner ring being placed eccentrically. Numerical simulation was performed to guide the selection of specimen dimensions and to reveal the stress concentration phenomenon. Experiments were conducted to record cracking time and cracking locations. It is seen that, compared with RRTM, the eccentricity introduced in RERTM and RSERTM will give rise to stress concentration, guide cracking location, and noticeably shorten cracking time.