A smart connection materials exploration used in prefabricated construction: Effects of MWCNTs and MSF on self-sensing grout

Developing a self-sensing high-strength grout (SSHG) has a great competition in structural NDT of prefabricated construction. However, only a limited number of studies have addressed the topic of SSHG, and comprehensive studies on its preparation and properties have not been extensively reported. In this study, the effects of MWCNTs (length of 10 mu m, diameter of 15 nm) and Microsteel fibers (MSF, length of 8 mm, diameter of 0.12 mm) as fillers on fundamental properties, conductivity and load sensitivity were investigated systematically. The results showed that the introduction of fillers affected the workability and volume expansivity of the grout to varying degrees, despite improvements in mechanical strength. For a specified w/b ratio of 0.24, the volume incorporation of MWCNTs should not exceed 0.2 % to ensure adequate fluidity. The DC resistivity changes under different curing age and ambient temperature (20 degrees C, 20 degrees C and 40 degrees C) were explored, confirming that the incorporation of 0.15-0.2 vol% MWCNTs can mitigate the interference of aging and temperature fluctuations. The optimal sensing capacity of SSHG was validated by two types of cycle compression, the FCR of 0.2 vol% MWCNTs and 0.15 vol% MWCNTs & 0.05 vol% MSF reached to 30.21 % and 30.96 % under 18.75 MPa compression respectively. The sensing mechanism and stability were further discussed. This provides a new idea for NDT of prefabricated construction.