A NEW METHOD TO OBSERVE 3-DIMENSIONAL FRACTURES IN CONCRETE USING LIQUID-METAL POROSIMETRY TECHNIQUE

The technique described here makes it possible to observe microcracks in concrete in three-dimensions with apertures as small as 0.1 mu m. A n alloy with a low melting point was used to penetrate cracks and pore s in cylindrical specimens of normal and high-strength concrete subjec ted to uniaxial and confined compressive stresses. After the induction of fractures, an alloy was solidified to preserve the shapes of stres s-induced microfractures as they exist under load. After the alloy was solidified, the surface of the specimens were etched with 1 molar hyd rochloric acid, leaving a skeleton of alloy network on top of the new surface. Micrographs using a Scanning Electron Microscope (SEM) reveal ed a complex three-dimensional network of metal-filled fractures and v oids. (C) 1997 Elsevier Science Ltd.