An experimental method for dynamic tensile testing of concrete by spalling

A new application of the spalling phenomenon in long specimens is reported in this paper. The new experimental technique is based on an experimental s etup which consists of an air launcher of cylindrical projectiles with a Ho pkinson bar as a measuring tool and a relatively long concrete specimen in contact with the bar. The incident compression wave transmitted by the Hopk inson bar into the specimen is reflected as a tensile wave causing spalling . Although such configurations have been reported in the past, the main adv antage of the present approach lies in the application of the detailed anal ysis, based on the wave mechanics with dispersion, to extract the specimen behaviour. Such an approach leads to an exact estimation of the local failu re stress in tension at high strain rates, even above 100 s(-1). This paper demonstrates, using two series of tests on concrete, that this experimenta l setup can cover one decimal order of strain rates, from similar to 10 to similar to 120 s(-1). The tests performed at high strain rates on wet and d ry concrete have indicated that the tensile strength is substantially influ enced by the loading rate or strain rate. The absolute value of the failure stress for wet and dry concrete is almost the same for a particular strain rate, which does not occur when subject to low strain rates in tension or compression. A brief discussion is offered on a high rate sensitivity of co ncrete strength in tension at high strain rates. (C) 2001 Elsevier Science Ltd. All rights reserved.