Strain And Abrasion Sensing Properties Of Nickel Cement-based Composite

Offshore transportation project, such as bridges, is an important support for socialdevelopment, whose security service is a major concern of the nation. Structural Healthmonitoring (SHM) provides an effective means to evaluate the safety of such structuresso as to guarantee their security service. Abrasion and strain sensing are the two majorproblems that SHM in offshore structures face. Sensors are fundamental parts of SHMsystems. Cement-based sensing material, with its good compatibility with the matrix-concrete, has become one of the hotspots for SHM in civil engineering. Therefore, thispaper, with its aim to monitor the abrasion and strain in offshore bridges, investigatedthe anisotropic conductivity of nickel powder cement-based composite and its abrasionand strain sensing characteristics, and then developed optimization methods of materialpreparation based on abrasion and strain sensing performance.Firstly, the composite with better electrical properties was prepared by changingthe alignment of nickel powder in cement base via the introduction of an externalmagnetic field, so as to create the anisotropic conductivity at micro-scale. To detect theelectrical properties of the material filled with different amount of nickel powders, theelectrical behavior based on the resistivity of the material and the principle which itfollowed were studied. The effect of the arrangement of Nickel powders in the base onelectrical properties under different magnetic field intensity was presented. Based on thechange of the electrical properties with nickel powders content and magnetic fieldintensity, combining with the study of nickel powders dispersion in the water, wedetermined the most profitable preparation of the anisotropic conductive material.Secondly, focusing on the sensitivity and stability of strain sensing (piezoresistiveproperties) in cement-based composites, the effect of anisotropy on the piezoresistivesensing properties was studied. Specifically, the characters that affect the piezoresistiveproperties were investigated, such as the nickel powder volume content, magnetic fieldstrength, Poisson’s ratio.Finally, based on the relationship of changing rate of resistance and that of abrasion,the erosion characteristic and its mechanism of the material filled with different amountof Nickel powders were investigated under dry aridity and saturated condition. Bycomparison of the sensitivity of the scouring electrode, the stability of the referenceelectrode, we determined the optimal scheme of the electrode arrangement which is ableto compensate the temperature and humidity effect.