PSI - Issue 67

Oscar Aurelio Mendoza Reales et al. / Procedia Structural Integrity 67 (2025) 8–16 Mendoza Reales et.al. / Structural Integrity Procedia 00 (2024) 000 – 000

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3°C/min, when temperature was stabilized, compressive loading was applied. Voltage was applied for 20 minutes before mechanical loading. Mechanical load was recorded together with electrical resistivity and deformation of the SSCC measured using the copper plates and strain gauges, respectively. Each test was performed two times to better understand the repeatability of the result. The FCR versus deformation (ε) curves were used to determine the gauge factor (GF) for each SSCC by fitting equation 3 to the results. = (3 )

Fig. 3. SSCC placed in the compression testing machine equipped with a heating furnace and connected to the voltage source and data acquisition system.

3. Results This section presents and discusses the effects of temperature over the electrical response of a SSCC. The section is divided in two parts. The first part shows the effect of temperature in transient state on the electrical resistivity of the composite, without mechanical load application, while the second part shows the effect of temperature in steady state on the piezo-resistive response of the material. 3.1. Effect of temperature in transient regime over the resistivity of SSCC The effect of temperature in transient regime over the dimensions and the electrical resistivity of the SSCC is presented in Fig. 4. Deformations measured by the strain gauges were used to determine the thermal expansion coefficient of both SSCC. Results are presented in Fig. 4a. It was found that SSCC1 presented a thermal expansion coefficient of 3.58 10-6/°C and SSCC2 presented a coefficient of 5.66 10-6/°C. These values are in the same order of magnitude than previous literature reports for mortars, Zeng et al. (2012), Sicat et al. (2013). Regarding the electrical behavior presented in Fig. 4b, it was found that while temperature increased from 25 to 60 °C, electrical resistivity of the SSCCs decreased proportionally. This behavior has been previously reported for plain cement matrices and explained by the relationship between resistivity and temperature of the ions in the pore network, McCarter et al. (2007). This decrease in resistivity has also been reported in carbon nanotubes/cement composites, Cerro-Prada et al. (2021), and has been related with a higher connectivity of the pores filled with ionic species, due to the presence of carbon nanotubes, and the increase in conductivity of the matrix already detailed in the introduction