Abstract:
The effect of water-to-cement ratio
(w/c) on the piezoresistive behavior of smart
cement was investigated. The sensing property
of the smart cement was modified with 0.1%
carbon fiber (CF) and the behavior was
investigated up to 28 days of curing. Electrical
resistivity was identified as the sensing and
monitoring property for the smart cement. The
initial resistivity (ρo) of the smart cement
decreased from 1.03 Ω-m to 1 Ω-m and 0.9 Ω-m,
a 3% and 12% reduction when the w/c ratio was
increased from 0.38 to 0.44 and 0.54 respectively,
higher than the changes in the initial unit
weights of the cement slurry. For the smart
cement the electrical resistivity increased with
the applied compressive stress (New
Technology). The piezoresistive axial strain of
the smart cement at failure with water-cement
ratio of 0.38 and curing of 28 days was over
300% compared to the failure strain cement of
0.2%, 1500 times (150,000%) higher make it a
highly sensing material. The Vipulanandan p-q
piezoresistive model predicated the
piezoresistive compressive stress – change in
resistivity relationship of the smart cement very
well. Linear correlations were observed between
resistivity index (RI24hr) and compressive
strength of smart cement for different curing
times.
