MECHANICAL CHARACTERISATION AND FRACTURE PROCESS OF CONCRETE AT HIGH STRAIN-RATE

摘要

A testing programme over large range of strain-rates (10~(-6) to 10 s~(-1)) including those of seismic and impact loading, has been performed in tension on cube specimens of plain concrete with aggregates of 5, 12 and 25 mm size, using hydraulic and large Hopkinson bar equipment. A new testing apparatus consisting of large aluminium Hopkinson bar bundles was used for more precise measurements of the mechanical properties in particular of the softening branch of the stress strain diagram. The new Hopkinson bar bundle test allowed in particular the measurement of: the place(s) and time(s) of fracture initiation(s) and propagation over the specimen cross section; the residual resisting cross section during fracture propagation.