PSI - Issue 78

Paolino Cassese et al. / Procedia Structural Integrity 78 (2026) 607–614

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In a linear field of stress/deformation, the sensitivity is commonly expressed by a constant gauge factor ( GF) , which allows for signal conversion from the electrical to the mechanical domain. Concerning the tests carried out in the present study, the GF of the SSCCs specimens can be obtained starting from the graph of the recorded FCR vs  through a linear regression analysis implemented in Matlab. The inverse of the slope of the fitting line provides the GF value. Two different conditions were considered for the regression model: (i) fixed intercept equal to zero; (ii) free intercept to achieve the best fitting score in terms of coefficient of determination (R 2 ). Fig. 6 shows the results for the two specimens. Both are characterized by a good linearity of the self-sensing response for the whole compressive load range investigated, although less dispersion is observed for the specimen C075W042, because of the reduced signal drift and noise, along with a considerably higher sensitivity.

GF = 45.6 R 2 = 0.86 GF = 43.5 R 2 = 0.86

GF = 81.9 R 2 = 0.97 GF = 67.1 R 2 = 0.92

(a)

(b)

Fig. 6. Calibration of specimens C050W050 (a) and C050W042 (b) under compressive loading.

Conclusions The effect of the w/c ratio on the performance of SSCCs obtained by adding COOH-functionalized MWCNTs to cement paste in the amount of 0.75% by weight of cement has been investigated in this study through experimental electromechanical tests. Two specimens were tested under cyclic compressive load in the elastic range, characterized by w/c ratio values of 0.50 and 0.42, respectively. The electrical resistance change due to piezoresistivity was obtained from four-probe AC measurements. Both specimens showed an approximately linear self-sensing response within the applied load range of 3-5 kN, although the specimen characterized by a lower w/c ratio provided less dispersed results, a reduced signal drift and noise, and a considerably higher sensitivity. The obtained results agree with previous studies in the literature, even if further tests are necessary to confirm the current findings and to investigate also the effects of different MWCNT concentrations and/or load levels. Acknowledgements The present study has been carried out in the framework of the PRIN 2022 “SUCCESS - SUstainable self-sensing Cement- based CompositES for dynamic monitoring of civil Structures” (code “2022L9PSNW”), funded by European Union - Next Generation EU, Missione 4 “Istruzione e Ricerca”, Componente C2, Investimento 1.1, “Fondo per il Programma Nazionale di Ricerca e Progetti di Rilevante Interesse Nazionale (PRIN), CUP H53D23001330006, CUP B53D23006210006, whose financial support is gratefully acknowledged.