Volume 7, Issue 9 (October 2010)
A Dual Concentric Ring Test for Evaluating Residual Stress Development due to Restrained Volume Change
A new test is being developed to evaluate the performance of concretes undergoing both expansion and shrinkage during hydration and/or temperature changes under mechanically restrained conditions. The standard restrained ring test (ASTM C1581-09) is a simple, economical method to evaluate a concrete mixture’s susceptibility to develop shrinkage cracking when it is restrained. The standard test only provides restraint against samples that shrink at isothermal temperature and cannot be used to characterize materials undergoing expansion. Further, the conventional restrained ring test is difficult to apply in cases in which the concrete undergoes large variations in temperature since the restraint changes dimension under heating and cooling. This paper describes a test that was designed to overcome both of these limitations. The new dual concentric ring test provides restraint for both shrinkage and expansion and has incorporated the ability to study thermal stresses by using a restraining ring having a very low thermal expansion coefficient. This paper will discuss the design and construction of the test device and will present preliminary data that characterizes its ability to quantify and evaluate restrained expansive, shrinkage, and thermal stresses.