Drop-Weight Impact Resistance of Ultrahigh-Performance Concrete and the Corresponding Statistical Analysis

An experimental and statistical study on the impact resistance of ultrahigh-performance concrete (UHPC) is presented. The impact resistance was evaluated by conducting the drop-weight impact test with a hammer of 10 kg following ACI Committee 544 (ACI 544.9R-17). Three mixture types, namely ordinary concrete, nonfibrous UHPC matrix, and UHPC were designed, and each type was prepared with 40 cylindrical specimens with dimensions of Phi 150 x 63.5 mm for impact test. The commonly used distribution functions for material properties (normal distribution and Weibull distribution) were selected to examine the test data, and the goodness of fit of these two distributions was evaluated using a Anderson-Darling test. Results indicate that the designed UHPC endured an average of 623 drops of impact weight before the first crack, while the ordinary concrete and nonfibrous UHPC matrix showed the first crack only after 26 drops and 17 drops, respectively. The higher-strength nonfibrous UHPC matrix broke with a fewer number of drops under impact load than the ordinary concrete (with coarse aggregate) due to the greater brittleness of the UHPC matrix. Both the normal and Weibull distribution can describe the impact resistance of ordinary concrete, while the nonfibrous UHPC matrix and UHPC showed poor fitness to either the normal or Weibull distribution. Statistical analysis results indicate large scatters in the impact resistance of UHPC, and tests with small sample size may result in unreliable judgment. In this paper a baseline of UHPC drop-impact resistance to inspire proper qualification of UHPC members designed to withstand impact loading is provided. (C) 2021 American Society of Civil Engineers.