Abstract:

The physical and mechanical parameters (peak stress, peak strain), failure mechanism and post-peak strain softening (softening performance) of concrete with different sizes under different strain rates were researched through uniaxial dynamic compression test. The test was conducted on cubic concrete specimens of different sizes (150mm,300mm, 450mm) at different strain rates (10^-5/s, 10^-4/s, 10^-3/s, 10^-2/s) by large multi-functional electro-hydraulic servo static triaxial machine. Results showed that concrete’s peak stress and peak strain both reduced with the increase of specimen size; concrete strength increased with the increase of strain rate; after the peak strain occurred, the absolute value of the stress-strain curve slope increased whereas the ductility reduced as the specimen size increases. For the specimen size of 150mm, concrete softening strengthened with increasing strain rate, and the softening degree increased; while for the specimen size of 300mm and 450mm, the softening weakened when strain rate increased, but when the strain rate increased to a certain value, the softening became apparent. At the same strain rate, the softening was increasingly apparent with the increase of specimen size.

Key words: concrete, size effect, dynamic characteristics, compressive strength, softening characteristics, stress-strain relationship