Effect of Confinement on the Fracture Behavior of Concrete under Compression

This paper presents the results of experimental studies of the behavior of concrete under compression. Cylindrical specimens of concrete were subjected to testing under uniaxial and confined compression. An alloy with a low melting point was used to impregnate the cracks and pores in the specimen. At the stress of interest, this alloy was solidified to preserve the stress-induced microcracks as they exist under load. Such a technique not only allows one to observe microcracks as they exist under load, but also facilitates observing the microcracks in three dimensions. Scanning electron microscopy (SEM) was employed to capture images from the cross sections of the concrete specimens. A comprehensive image analysis was performed on cracking pattern developed in the concrete samples. measurements on backscatter electrons (BSE) images was performed on the computerized images to determine the crack orientation, density, length of the compressive stress-induced microcracks in concrete and the effect of confinement on microcrack behavior. 1843 1 preservation of stress-induced structure and the identification of induced by loading and unloading are important to understand the ..... JI. ... ,..., ............ ....," ........... ....,, for the generation, propagation interaction of stress- microcracks complex systems such as concrete. It is to understand how the formation, growth and interaction of microcracks leads to macrofracture, which are usually the form of failure observed in engineering practice. This paper presents direct observations size, orientation and interaction of microcracks in concrete specimens as they exist under load. The proposed method involves the of a metal liquid phase, Wood's metal, which a point below boiling point of water, to preserve of stress-induced microcracks in concrete.