Multifunctional carbon fiber reinforced alkali-activated composites: Performance stability under electrical current-induced thermal cycles

With growing emphasis on sustainable and multifunctional construction materials, this study addresses the critical need for durable electrothermal composites by investigating the performance evolution of multifunctional carbon fiber reinforced alkali-activated composites (AAC). The electrothermal performance of the AAC was refined through the investigation of multiple parameters, including the carbon fiber (CF) dosages (0.1–1.0 vol%), fly ash to ground granulated blast furnace slag ratios, and sand incorporation on conductive network formation and long-term stability. Using comprehensive microstructural characterization techniques, the underlying mechanisms governing AAC performance are identified. The findings of this work reveal that: 1) Carbon fibers can enhance the mechanical properties of the composites by promoting the alkali-activated reaction; 2) Increasing the carbon fibers dosage shifts the dominant conduction mechanism of the composites from ionic to electronic, with a percolation threshold at 0.6 vol%. The newly developed equivalent circuit models precisely describe the electrochemical behavior of the composites; and 3) Uniform and stable heat generation can be realized through optimized ground granulated blast furnace slag content, electrode configuration, sand incorporation and moisture levels. The refined composites maintain consistent performance (∼43.3 °C) after self-heating cycles, demonstrating their potential for sustainable heating applications in building technologies.