Enhancing bond performance: Carbon fiber reinforced polymer bar interaction with multi-walled carbon nanotubes cementitious composites in chloride-exposed conditions

A number of studies have been conducted on strengthening structures using carbon fiber reinforced polymers (CFRP) and improving the performance of cement fillers using multi-walled carbon nanotubes (MWCNT). In this study, bond characteristics of CFRP bars to MWCNT cementitious composites is investigated in chloride environment. The bonding advantage of CFRP bars and MWCNT cement filler is due to the mechanical properties of MWCNT and the ability to utilize the corrosion resistance provided by CFRP. This enables highly durable composites that can resist corrosion in chloride-rich environments. A total of 36 pullout (PO) tests were performed on CFRP bars set into MWCNT cementitious composites. Mercury Intrusion Porosimetry (MIP) test and field-emission scanning electron microscopy (FE-SEM) confirmed a decrease in porosity upon addition of MWCNTs. MWCNTs filled the pores of cement with nanoscale particles and increased the bond area of the cement composite with CFRP bar. The reduction in porosity between cement and aggregate not only enhanced strength but also improved chloride resistance. However, agglomeration began at 1.0-wt% concentration owing to van der Waals forces. The results revealed that the 0.5-wt% MWCNT cementitious composite with CFRP bars had the highest bond strength in a chloride environment.