Effect of Multiwalled Carbon Nanotubes on Sensing Crack Initiation and Ultimate Strength of Cement Nanocomposites

摘要

Sensing crack in multiwalled carbon nanotube (MWCNT)-reinforced cement under compression stress was investigated to aid in the temporal detection of crack initiation. Cement-based nanocomposite specimens were prepared with fixed proportions (e.g., water/cement ratio and sand/cement ratio) and varying concentrations of MWCNTs (0.01%, 0.02%, 0.1% and 0.2% by weight of cement). Microstructure was analyzed by means of a scanning electron microscope to show crack bridging and EDX spectroscopy to confirm the existence of MWCNTs in cement paste. Crack monitoring was presented through the variation of the temporal slope of electrical resistance during compression stress of nanocomposite samples. It is shown that temporal slope variation can be used as an index for crack warning owing to its well-defined patterns with distinct peaks that correlate with crack initiations and propagation. A significant increase in ultimate compressive strength with MWCNT concentration more than 0.1 wt% with respect to cement was observed.