Development of Self-Sensing Cementitious Composites with Magnetically Aligned Particles

Publication Type:
Thesis
Issue Date:
2022
Full metadata record
Self-sensing cementitious composites as a type of smart material, have the ability to sense external loads and environmental changes through piezoresistive properties. They have the advantages of high sensitivity, good compatibility, low maintenance cost and hence great potential to be applied in structure health monitoring, weight in motion and traffic detection. The sensing function of the composites is achieved via the network formed of conductive particles which are randomly dispersed in the cement matrix. However, this isotropic network may not be used to its full capacity in a unidirectional loading scenario, and the composites with nickel powder share a disadvantage of high particle demand. This leads to a diminishment in mechanical strength and cement workability. This study introduces an innovative method to align the nickel particles into chain patterns utilising the magnetic field in the fresh stage of cement and the structure is retained with the solidification process. Resistance measurement shows that resistivity declines significantly and the percolation threshold is advanced to a much smaller particle content when using the proposed method. Additionally, the anisotropic conductive chains exhibit enhanced piezoresistive performance and significant sensitivity with high gauge factor. Also investigated here are the influence of ferromagnetic particles morphology and magnetic parameters such as magnetic field strength and duration, the objective being to greatly improve the composites’ piezoresistive performance. Finally, the embedment of proposed cement sensors in a beam signifies a further contribution to the possibility of using magnetically aligned nickel particles in practical situations.
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