Preserving microstructure of concrete under load using the Wood’s metal technique

Abstract A special experimental technique was developed which made possible the preservation of microstructure and the compressive stress-induced microcracks in concrete as they exist under applied loads. Cylindrical specimens of concrete were tested under uniaxial and triaxial compression. The resulting induced cracks were impregnated with a metal alloy, Wood’s metal, that liquefies at higher temperatures (70–85°C), but is solid at normal temperatures. At the stress of interest, this alloy was solidified to preserve the stress-induced microcracks as they exist under load. Scanning Electron Microscopy (SEM) was employed to capture images from the cross sections of the concrete specimens. Stereology presents the geometrical statistical background for relating three-dimensional structures to their two-dimensional sections. Stereological estimates were obtained for total crack extension per unit of volume. Further, two-dimensional features of the cracks were analyzed in the section plane, such as orientation distribution, and length.