Smart Cement-Based Materials Reinforced with CNT-Grafted CFs: Preparation and Performance Evaluation

Smart cement-based materials have the potential to monitor the health of structures. The performances of composites with various kinds of conductive fillers have been found to be sensitive and stable. However, poor dispersion of conductive fillers limits their application. This study adopted the coupling agent method to attach carbon nanotubes (CNTs) onto the surface of carbon fibers (CFs). The CNT-grafted CFs (CNT-CFs) were adopted as conductive fillers to develop a CNT-CF-incorporated cementitious composite (CNT-CF/CC). The feasibility of this approach was demonstrated through Scanning Electron Microscopy (SEM) analysis and X-ray Photoelectron Spectroscopy (XPS) analysis. The CNT-CF/CC exhibited excellent conductivity because of the introduction of CNTs compared with the CF-incorporated cementitious composite (CF/CC). The CNT-CF/CC reflected huge responses under different temperatures and moisture contents. Even under conditions of high humidity or elevated temperatures, the CNT-CF/CC demonstrated stable performance and exhibited a broad measurement range. The introduction of CNT-CFs also enhanced the mechanical properties of the composite, displaying superior piezoresistivity. The failure load for the CNT-CF/CC reached 25 kN and the maximum FCR was 24.77%. In the cyclic loading, the maximum FCR reached 20.03% when subjected to peak cyclic load at 45% of the failure load. The additional conductive pathways introduced by CNTs enhanced the conductivity and sensitivity of the composite. And the anchoring connection between CNT-CFs and the cement matrix has been identified as a primary factor enhancing the stability in performance.