Nanoscale characterization of engineered cementitious composites (ECC)

Engineered cementitious composites (ECC) are ultra-ductile fiber-reinforced cementitious composites. The nanoscale chemical and mechanical properties of three ECC formulae (one standard formula, and two containing nanomaterial additives) were studied using nanoindentation, electron microscopy, and energy dispersive spectroscopy. Nanoindentation results highlight the difference in modulus between bulk matrix (~30 GPa) and matrix/fiber interfacial transition zones as well as between matrix and unreacted fly ash (~ 20 GPa). The addition of carbon black or carbon nanotubes produced little variation in moduli when compared to standard M45-ECC. The indents were observed by electron microscopy; no trace of the carbon black particles could be found, but nanotubes, including nanotubes bridging cracks, were easily located in ultrafine cracks near PVA fibers. Elemental analysis failed to show a correlation between modulus and chemical composition, implying that factors such as porosity have more of an effect on mechanical properties than elemental composition.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94205/1/sakulich-ccr-ECC-nanoindentation.pd

Self-Healing Characterization of Engineered Cementitious Composite Materials

This research investigates the self-healing behavior of engineered cementitious composite (ECC) materials. Crack characteristics, resonant frequency (RF) recovery, and the effect of wet-dry conditioning cycles were studied. Characterization of the self-healing products in ECC materials was carried out with an environmental scanning electron microscope-energy dispersive spectroscopy system (ESEM-EDS), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD). According to the experimental results, wet-dry conditioning cycles aid self-healing, most of which occurs before four to five cycles. The products of self-healing were identified as mainly C-S-H and calcite. These products almost completely bridge cracks less than 50µm wide. Overall, the self-controlled tight crack width (CW) of ECC materials tailored for high-tensile ductility encourages robust self-healing behavior in both young and mature (3- and 90-day-old) ECC specimens, respectively.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94201/1/self-healing-characterization-lili.pd