In the present work, dynamic tensile strength of concrete is experimentally investigated by means of spalling tests. Based on extensive numerical simulations, the paper presents several advances to improve the processing of spalling tests. The striker is designed to get a more uniform tensile stress field in the specimen. Three methods proposed in the literature to deduce the dynamic strength of the specimen are discussed as well as the use of strain gauges and a laser extensometer. The experimental method is applied to process data of several tests performed on wet microconcrete at strain rates varying from 30 to 150/s. A significant increase of the dynamic tensile strength with strain-rate is observed and compared with data of the literature. In addition, post-mortem studies of specimens are carried to improve the analysis of damage during spalling tests.

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Intense damages as scabbing on front face, spalling on rear face, radial cracks are observed in concrete structures when subjected to the impact of a kinetic striker. To characterize the dynamic strength and damage of concretes under such loadings one may perform spalling tests and EOI (edge-on impact) tests. Both tests have been conducted with dry and wet specimens of a micro-concrete named MB50. The tests revealed a remarked effect of strain-rate and free water on the dynamic response of the concrete. In parallel, bending tests and direct tensile tests have been performed with dry and saturated concrete samples considering large and small effective volumes and the results have been compared with five sets of data given in the literature with the same material. A scale effect is observed in agreement with prediction of Weibull theory. Moreover, an anisotropic damage model that describes the initiation of cracks and the obscuration of critical defects under high strain-rate tensile loading is presented. It allows accounting for the influence of loading-rate and free-water on the dynamic strength and damage of concrete observed in EOI and spalling tests.

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