Abstract:
In this research, the electrical resistivity of the cement-based sensors, which are mainly made of
cement pastes and supplemented with other two electrically conductive materials (i.e. Carbon Fiber
and Graphite Powder), was studied. Various mix compositions were tested in which three water to
cement ratios (i.e. 0.3, 0.4 and 0.5), two volume fraction of carbon fiber (i.e. 2 and 4%), and three
amounts of graphite powder (i.e. 2, 4 and 10% by wt. of cement), were varied. Their electrical
resistances and their compressive strengths were measured. The aging effect on the electrical
resistance of the cement based sensor at 3, 7, 14 and 28 days was also evaluated. The test results
indicate that both carbon fiber and graphite powder reduce the electrical resistivity. The carbon fiber
increases the ultimate compressive strength of cement-based sensor but the graphite powder decreases.
In addition, the resistivity responses of the cement-based sensor under compressive forces were
experimentally investigated and reported herein as a fractional change in resistivity (FCR).
The compression test controlled to achieve three different compressive strains (i.e. 0.0025, 0.005 and
0.01) was conducted. It is found that the responses of most cement-based sensor was not viable at the
compressive strain higher than 0.005. Moreover, the FRC of the carbon fiber cement-based sensors
becomes more negative as the compression is increased, which indicates the higher conductive
response. In contrast to that, the graphite powder cement-based sensor yields positive FCR when the
w/c ratio is low at 0.3 and turns the FCR value toward zero when the w/c ratio is higher.