Fatigue and Dynamic Loading
Pages 51

Direct-tension, splitting tensile and direct-compression tests were performed on 51-mm diameter, 51-mm long specimens of concrete at strain-rates of 10“7 to 102/sec. A standard material test machine was used for the low rates and a 51-mm diameter split-Hopkinson pressure bar was used to test at the high rates. The direct-tension and splitting tensile specimens usually fractured into two major pieces at strain rates of 10“7 to 10/sec. The compressive specimens fractured into a large number of fragments at all strain-rates, but a definite decrease in particle size was evident at strain rates above 25/sec. A sieve analysis of the fractured compressive specimens showed a definite correlation between actual average size and that predicted by linear fracture mechanics. Both the experimental tensile and compressive strength data were found to be proportional to the cube root of the strain-rate for the high strain-rates.