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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sands with a 2.4 mm maximum particle size from IPT, Brazil. A second-generation plasticizer (SP) was obtained from BASF Chemicals in Brazil. Copper plates were used as electrodes. 2.2. Methods This section describes the methods used to fabricate the SSCC samples and study the effects of increasing temperature on their electrical resistivity and piezo-resistive capabilities. The effect of temperature was studied in a transient regime, by heating the samples up to a certain temperature and monitoring their electrical resistivity simultaneously, and in steady regime, by heating the samples to a certain target temperature and monitoring their piezo-resistive response at constant temperature. MWCNT were dispersed in deionized water with an ultrasonic tip processor, which was configured at a 40% amplitude and operated in 20-second intervals. The MWCNT were introduced at a concentration of 2% by mass, and a superplasticizer was employed as the dispersing agent in a ratio of 1:1 with respect to MWCNT. The ultrasonic tip delivered a total energy of 110 kJ per gram of MWCNT during the dispersion process. The SSCC was manufactured by introducing MWCNT into a mortar blend consisting of cement, deionized water, standardized quartz sand, silica flour, and VMA. The mass proportions of each component for all samples tested is presented in Table 1. The prepared mortars were cast into 40 mm cubic acrylic molds and four copper electrodes were inserted into the mixture after molding. Samples were kept in a humid environment and after 48 hours were removed from the mold and cured in a humid environment for 40 days. 2.2.1. Sample fabrication

Table 1. Mass proportion of the SSCC studied in this work. (* by mass of cement). Sample MWCNT (%*) Silica flour:Cement Sand:Cement Water:Cement

VMA (%*)

SSCC1 0.50 SSCC2 0.50

0.13:1.0 0.13:1.0

1.0:1.0 0.75:1.0

0.5:1.0 0.5:1.0

0.10 0.15

Following the curing process, the SSCC underwent a 5 day drying period in an oven set at 40 ºC to eliminate any residual free water. Subsequently, two strain gauges were glued to the lateral surfaces of the samples, and copper wires were soldered to both the copper electrodes and strain gauges. After this step, two coats of epoxy paint were applied to the surface of the SSCC to function as a barrier, preventing moisture exchange with the external environment and also preventing electrical conduction between the SSCC and the surface of testing equipment. Fig. 1 illustrates the final product achieved through this series of procedures.

(a) (b) Fig. 1. SSCC fabrication. (a) acrylic mold with copper plates, and (b) SSCC coated with epoxy paint.