Dynamic fracture investigations of ultra-high performance concrete by spalling tests

Abstract

Ultra-High Performance Concrete (UHPC) is an innovative cement based material with superior strength for engineering structures. The mechanical properties of the cementitious composite depend on its exact composition and need to be determined experimentally. Whereas several standard tests for the static loading regime exist, dynamic data such as tensile strength and failure load are difficult to measure.This contribution presents an experimental method to identify the material properties under impact loading. By means of a modified Hopkinson pressure bar, cylindrical UHPC specimens of different compositions without fiber are examined in strain rates of approximately 30s-1. Assuming uniaxial wave propagation, the resulting stress states are analyzed and the specimens’ dynamic elastic modulus, tensile strength and specific fracture energy are determined. Numerical fracture simulations in the sense of an inverse analysis prove the experimental approach valid. The agreement between both, experimental observations and numerical results, show that the obtained parameter are reliable and suitable for predictive simulations.