Fiber-matrix interface enhancement in engineered geopolymer composites using cellulose nanofibers based on in-situ polymerization

This paper studied self-assembled cellulose nanofibers (SCNF) with in-situ polymerization potential, aiming to enhance the fiber-matrix interface bonding of engineered geopolymer composites (EGC). The freeze-thawing method was used to introduce cellulose oligomers into the alkaline solution, ensuring the simultaneous occurrence of SCNF self-assembly and geopolymerization during curing. This process facilitated the formation of interpenetrating organic-inorganic networks within EGC. Microstructural characterization confirmed that SCNF improved the fiber-matrix interface through physical bridging and chemical bonding. Single fiber pullout test showed that SCNF increased the frictional bond by 18.6 % and the chemical bonding energy by 657 %, while reducing the slip-hardening coefficient β by 68.6 %. The results revealed a two-fold effect of SCNF: the interface bonding was strengthened but the slip-hardening behavior of PVA fibers was suppressed. Additionally, compressive and uniaxial tensile tests were conducted to evaluate the modification effect of SCNF on the mechanical properties of EGC. The optimal SCNF content was determined to be 0.5 wt%, which improved the compressive strength, tensile strength, strain capacity, and energy absorption of the EGC by 46.3 %, 44.2 %, 32.6 %, and 93.1 %, respectively. These findings provide direct and quantitative support for developing high-performance geopolymer composites.