Experimental Studies on Dynamic Response of Hardened Cement Paste

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Title: Experimental Studies on Dynamic Response of Hardened Cement Paste

Author(s): David Z. Yankelevsky and Itzhak Avnon

Publication: Special Publication

Volume: 175

Issue:

Appears on pages(s): 199-214

Keywords: cracking (fracturing); dynamic loads; explosions; hardened paste structure; tensile strength

Date: 12/1/1998

Abstract:
This paper is concerned with the description and explanation of Hardened Cement Paste (HCP) response to dynamic (explosive) loading. An experimental testing technique had been developed to study the dynamic cracking of HCP samples, using cylindrical explosive microcharges. Following the initiation of the microcharge, radial cracks propagate and measurements of their growth may be conducted. Procedures to predefine the crack path have been investigated, like preparation of linear grooves along the sample. Predefining the crack path enabled relatively simple measurements of its propagation velocity. The dynamic crack propagation velocity was found to be relatively low, within the range of 70-200 m/sec. (about an order of magnitude lower than the theoretical value). The dynamic HCP failure process was found to be usually of multicrack type. Studies of michrocharge initiation near a samples boundary provided insight into the development of scabbing cracks and of their interaction with the radial cracks propagating towards the boundary. It has been found that that crack interaction is strongly dependent on the relationship between the stress wave velocity and the crack propagation velocity.