Ductility and piezo-resistivity behavior of fiber-reinforced cement composites with carbon black

Nowadays, the need for health monitoring of structure is arising using the cement composites-based sensor. Advanced sensing materials are used for continuously monitoring the condition of infrastructure throughout the service life. So, for this purpose cement composites-based sensors are used. These composites have low ductility. Most of the damage in the structure are due to tensile stresses. Analyzing the behavior of composites for ductility as well as sensing ability are the main concern. The composite is developed by 1:3 (cement: sand), W/C ratio is 0.55, and 7.5%wt carbon black (CB) and 1%wt fiber replacement of cement. The two fibers are used i.e., polypropylene (PP) and carbon fiber (CF) with different combinations. The fiber combinations (0%CF+1%PP), (0.25%CF+ 0.75%PP), (0.5%CF+0.5%PP), (0.75%CF+0.25%PP), (1%CF+0%PP) are used, but overall percentage of fiber will remain same. The curing period for the sample is 28 days. The compression and conductivity of composites will increase by the addition of CB and CF, but the ductility of composites will not increase until the addition of fibers. Addition of PP fibers tend to decrease the conductivity, but CF fiber in replacement to PP helps to increase the conductivity. Ultimate tensile strength of composites is maximum for a sample with (0.75%CF + 0.25%PP). The conductivity increases as the %age of CF increases and maximum at (1%CF + 0%PP). The reversible behavior of piezo resistivity is shown to be good with (0.5%CF+0.5%PP) and (0.75%CF+0.25%PP). Based on the study, it is recommended that to use the CB as filler material for enhancing the conductivity and fibers (PP & CF) for enhancing the ductility.