EXPERIMENTAL INVESTIGATION OF THE EFFECT OF STRAIN RATE ON THE CRUSHING STRENGTH OF A CELLULAR CONCRETE

The strain rate dependent compressive strength of an autoclaved aerated concrete (AAC) having a density of 600 kg m-3 was experimentally investigated between quasistatic and high strain rates (2x10-3-~4150 s-1) through quasi-static and dynamic compression, confined compression and indentation tests. High strain rate equilibrium and direct impact non-equilibrium compression tests in conjunction with the high strain rate confined compression and indentation tests were conducted in a compression Split Hopkinson Pressure Bar. The experimental results showed two different regions of the compressive strength-dependency on the strain rate: a low-strain rate-dependent region from quasi-static to ~18 s-1 and a high-strain rate-dependent region from ~18 s-1 to ~1000 s-1. The switch of the failure mode from the single axial cracking at quasi-static strain rates to the extensive axial and circumferential cracking at increasing strain rates was ascribed to both the axial and radial inertia. The dynamic increased factor (DIF=dynamic strength/static strength) showed an abrupt increase after ~18 s-1 as similar with the compressive strength. The mean confined and indentation strength values also increased as the velocity increased, while the mean confined compression strength values were shown to be comparable with the dynamic compressive strength values. The inertia and strain rate contributions to the enhancement of DIF until about 1000 s-1 were predicted by taking the quasi-static indentation strength as the full confinement strength.