EFFECTS OF STRAIN-RATE ON CONCRETE STRENGTH

The effects of strain rate on the tensile and compressive properties of plain concrete specimens 51 mm in diameter were studied both experimentally and numerically. Quasistatic tests at strain rates of 10(-7)/sec to 10(-3)/sec were conducted using a standard material test machine. Higher strain rate tests of 1.0/sec to 300/sec were conducted in a 51-mm-diameter split-Hopkinson pressure bar (SHPB). Numerical simulations of both the static and dynamic tests were conducted through a comprehensive finite element method investigation. Experimentally observed crack patterns agreed very well with the predicted numerical responses. Both tension and compression strengths increase with strain rate and exhibit a critical strain rate beyond which large increases in strength occur. This critical strain rate is approximately 5/sec for tension and approximately 60/sec for compression. Beyond these critical strain rates, the tensile strength shows a larger percentage increase than the compressive strength. The effect of moisture on the dynamic compressive strength of concrete was also examined in the experimental study.