Preliminary Investigation of Hand-Lay-Up Fabrication of Continuous Carbon Fiber-Reinforced Alkali-Activated Binder Composites

Continuous carbon fiber composites have high strength-to-weight ratios, excellent corrosion resistance, and impressive durability. In civil engineering, continuous carbon fiber reinforcement is commonly employed in carbon fiber-reinforced polymer (CFRP) systems, whereas its direct incorporation into low-carbon alkali-activated binder (AAB) matrices remains relatively unexplored. This study presents a preliminary investigation into the fabrication of continuous carbon fiber-reinforced alkali-activated binder (CFR-AAB) composites using a hand lay-up technique. To facilitate fiber impregnation and laminate fabrication, the AAB matrix was first optimized by varying the liquid-to-binder ratio, sodium silicate-to-sodium hydroxide ratio, and sodium hydroxide concentration to balance flowability, setting time, and compressive strength. Using the optimized AAB matrix, which satisfied the adopted flowability and initial setting-time requirements for hand lay-up fabrication while achieving a compressive strength of 48.6 MPa, CFR-AAB laminates containing 12, 24, and 36 carbon fiber plies with symmetric stacking sequences were fabricated and mechanically evaluated. The incorporation of continuous carbon fiber had only a limited influence on compressive strength, with all CFR-AAB configurations achieving values above 46 MPa. In contrast, flexural strength increased substantially from 4.21 MPa for the plain AAB matrix to 70–85 MPa for the CFR-AAB composites, representing more than a sixteen-fold improvement. Failure observations showed that the flexural response was governed mainly by interlaminar delamination and shear-related damage rather than fiber rupture, highlighting the importance of fiber–matrix and interlaminar interactions in controlling composite performance. Overall, this study demonstrates the technical feasibility of manufacturing CFR-AAB composites using a simple hand lay-up process and establishes a foundation for lightweight, low-carbon structural composites. Future research should focus on improving fiber–matrix interfacial bonding and impregnation quality, optimizing laminate configurations, and evaluating the long-term mechanical and durability performance of the composites.