Kamran Mostashar Nemati - Departments of Civil & Environmental Engineering and Construction Management,

This paper discusses the results of experimental studies of the micromechanical behavior of high-strength concrete subjected to different loading conditions.Cylindrical specimens of high-strength concrete were tested under uniaxial and triaxial compression. The resulting induced cracks were impregnated with a metal alloy 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. This experimental method allows the preservation and identification of cracks and pores in concrete as they exist under load. The specimens were then observed using Scanning Electron Microscopy (SEM) to determine the effect of different loading conditions on the crack behavior of highstrength concrete. Detailed analysis of the SEM images obtained from the highstrength concrete samples after crack induction revealed the profound effect of triaxiality as opposed to uniaxial testing on crack orientation, crack density and crack length. The crack density and the length of the microcracks decreased as the confining stress was introduced

Microcracks, High-strength concrete, Wood’s metal, SEM, Image analysis