Monitoring micro-crack healing in an engineered cementitious composite using the environmental scanning electron microscope

• ESEM with EDX used to characterize the origin of micro-crack healing in an ECC
• Evolution of healing precipitates studied at three specific locations over four weeks
• Specimens exposed to laboratory environment, followed by the natural environment
• Calcium carbonate is the main contributor to crack healing at the crack mouth.
• Outdoor exposure involving intermittent rain promotes additional crystal growth.

Environmental Scanning Electron Microscopy (ESEM) is used to study the origin of micro-crack healing in an Engineered Cementitious Composite (ECC). ESEM images were acquired from ECC specimens cut from pre-cracked, dog-bone samples which then subjected to submerged curing followed by exposure to the natural environment. The mineralogical and chemical compositions of the healing products were determined using the EDX facility in the ESEM. It is shown that the precipitation of calcium carbonate is the main contributor to micro-crack healing at the crack mouth. The healing products initially appeared in an angular rhombohedral morphology which then underwent a discernable transformation in size, shape and surface texture, from relatively flat and smooth to irregular and rough, resembling the texture of the original surface areas surrounding the micro-cracks. It is also shown that exposure to the natural environment, involving intermittent wetting/drying cycles, promotes additional crystal growth, which indicates enhanced self-healing capability in this environment.

Figure optionsDownload as PowerPoint slide