This paper studied the piezoresistivity of cement-based composite filled with nickel powder. Cement-based composites filled various content of nickel powder were fabricated. During the hardening procedure of cement-based composite, various strength of magnetic fields were applied on the composites with a set of Helm-holtz coils, which can generate an adjustable uniform magnetic field through changing the electric current. The aligning level of nickel powder was characterized with the scanning electron microscopy (SEM) pictures, which indicated that the aligning level of nickel powder increased upon the magnetic field strength, and the alignment of nickel powder leaded to a remarkable change in the characteristics of conductive network. The electrical property of cement-based composite filled with randomly distributed nickel powder is isotropic. After aligning the nickel powder, it becomes anisotropic. Furthermore, the anisotropic level is not only dependent on the magnetic field strength (alignment level), but also related to the content of nickel powder. An interesting finding given in this paper is that the highest anisotropic level of electrical conductivity is reached at the threshold content of nickel powder, which is the critical content of nickel powder to form a connected conductive network. Piezoresistivity of cement-based composite is also dependent on both the content and alignment level of nickel powder. When the content of nickel powder was lower than the threshold, the strain gauge factor of the cement-based composite increased upon its alignment level. However, for a large content of nickel powder that exceeded the threshold, the alignment of the nickel powder reduced the strain gauge factor.
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