Cellulose nanocrystals in cementitious composites: Dispersion strategies and enhancement mechanisms

Cellulose nanocrystals (CNCs) are bio-based nanomaterials with exceptional mechanical properties and high surface area, offering significant potential for enhancing the performance and sustainability of cementitious composites. While CNCs are known for their uniform dispersion in water, their behavior in the highly alkaline, cation rich environment of cementitious environment remains poorly understood. This study provides the first systematic investigation into the dispersion behavior of CNCs in a simulated cement pore solution. Results revealed that multivalent cations in the pore solution substantially reduce CNCs zeta potential, triggering severe agglomeration and compromising their reinforcing capability. To overcome this limitation, five dispersants were evaluated, all of which enhanced the dispersion of CNCs in the cement pore solution. Cementitious composites were subsequently prepared with 0.1 %, 0.2 %, and 0.4 % CNC, both with and without dispersants. Results showed that the combination of PCE and PAA improved 28-day compressive strength by up to 20 %, while SDS, Triton X-405, and Pluronic F127, despite enhancing CNC dispersion, reduced strength due to foam formation. This work not only reveals the critical role of surfactant selection in maximizing the benefits of CNCs in cementitious systems but also offers a practical strategy to unlock their full potential for developing high-performance, sustainable concrete.