## 4 Challenges and Solutions
### Temperature and Moisture Effects  
The influence of temperature and moisture on the electrical resistivity of multifunctional cementitious composites can present challenges when these materials are used for detecting strain, stress, and damage [190]. Consequently, it is essential to calibrate the electrical resistivity of self-sensing cementitious composites, incorporating compensation measures for environmental factors, during operational use [191]. For example, [PERSON] et al. [147] observed that temperature variations ranging from \(-20\)\({}^{\circ}\)C to \(100\)\({}^{\circ}\)C do not impact the repeatability and sensitivity of a multifunctional cementitious composite doped with CB, provided that compensation for temperature effects is implemented. Furthermore, the impact of moisture variations on electrical resistivity can be negligible when the concentration of conductive fillers reaches an optimal percentage. For example, it was observed that the effects of moisture content on the electrical resistivity of cementitious composites were diminished upon the incorporation of 20 wt.% graphite (i.e., the achieved percolation threshold), due to the establishment of an electron conduction mechanism, as opposed to an ionic conduction mechanism [192]. This aspect is particularly crucial when self-sensing features of multifunctional cementitious composites are employed for SHM and traffic detection. For instance, Figure 20 displays the relationship between electrical resistivity and MWCNT concentration [126]. The data in Figure 20 clearly show that the influence of curing age on electrical resistivity is significant when the MWCNT  
Figure 19: Effects of polarization on the electrical resistance of self-sensing cementitious composites containing MWCNT: (**a**) stress vs. time; (**b**) strain vs. time; (**c**) resistance vs. time [86], published by Elsevier (2020); (**d**) effects of CNT concentration on the polarization [189], published by Elsevier (2022). concentration is below 0.5%. However, at MWCNT contents exceeding 0.5%, changes in electrical resistivity due to curing become negligible. This indicates that internal moisture variations in multifunctional cementitious composites, attributable to curing age, do not significantly affect electrical resistivity when the concentration of conductive fillers surpasses the percolation threshold. Moreover, it is important to recognize that moisture variations impact electrical resistivity gradually, in contrast to the abrupt effects caused by cracks [149]. Given the minimal influence of moisture on the electrical resistivity of an optimally formulated multifunctional cementitious composites and the distinct resistivity trends in response to water and cracks, it can be asserted that such composites are suitable for SHM applications [7]. Although the calibration of the recorded data against environmental factors is essential, it should also be noted that self-sensing cementitious composites, which are responsive to temperature and moisture variations, can be advantageous for fire and moisture detection applications. For example, [PERSON] et al. [193] successfully developed a fire alarm sensor by integrating an optimal concentration of CFs into a cementitious material. [PERSON] et al. [194] reported a reduction in the compressive strength and increased non-linearity of the FCR of multifunctional cement paste with increasing water ingression. The variation in the electrical resistance of multifunctional cementitious composites due to water ingression depends on the concentration percentage of the conductive fillers [192]. The influence of water ingression on electrical resistance was negligible when the conductive concentration was greater than the percolation threshold. Considering the direct contact with conductive fillers at the joints within the percolation threshold, the electrical resistance decreased with decreasing moisture contents due to decreased contact resistance [171].