Large-Diameter Triaxial Kolsky Bar for Evaluating Very-High-Strength Concrete

The U.S. Army Engineer Research and Development Center (ERDC) uses quasi-static triaxial compression experiments as a basis to adjust its constitutive models to predict full-scale penetration events on hardened concrete structures. However, there is a fundamental knowledge gap between quasi-static and dynamic characterization of concrete specimens under complex stress states. Although triaxial Kolsky bars have been used previously for brittle materials, the bar diameter is typically in the range of 12–19 mm. In some cases, specimen sizes are much smaller than the bar such that dynamic failure is achieved. The inherent nature of concretes is such that they have substantial heterogeneity at this length scale; therefore, a larger diameter bar must be used to acquire bulk properties. To alleviate this problem, a state-of-the-art 50-mm-diameter triaxial Kolsky bar that operates with a maximum confining pressure of 200 MPa was used to perform initial experiments on a very-high-strength concrete (\( {f}_c^{\prime } \) ~ 130 MPa). The focus of our current stage of study is to optimize specimen preparation techniques while establishing standard operating procedures for the large-diameter triaxial Kolsky bar.