Cellulose nanocrystals and their utilization in cement-based composites: A comprehensive review

Cellulose nanocrystals (CNCs), renewable bio-based nanomaterials derived from cellulose, are emerging as sustainable and high-performance additives for cementitious systems. While prior studies have explored various nanomaterials in construction, no comprehensive review has focused exclusively on CNCs in cement-based composites. This paper addresses this gap by systematically synthesizing findings from fresh properties to long-term durability, highlighting both performance improvements and implementation potential. CNCs act as viscosity-modifying agents, reducing flow spread but increasing yield stress by up to 70%. Hydration studies confirmed a retarding effect, with initial and final setting delayed by 60 min and 2 h, respectively, while calorimetry indicated cement-type-dependent influences and enhanced early aluminate and sulfate hydration. At later ages, strength gains were evident, including a 20% increase in compressive strength at 28 d (0.8% vol. CNC), 32% flexural strength gain at 1.5% vol., and 33% tensile strength gain at 56 d (1% wt.). Durability improvements were also reported: drying shrinkage was reduced by up to 55%, carbonation depth by 38%, and frost resistance was enhanced with only 0.18% strength loss after 25 freeze-thaw cycles at 1% CNC content. CNC addition also increased thermal conductivity by 17%, suggesting multifunctional potential. This review establishes CNCs as promising nano-additives that refine microstructure, enhance mechanical properties, and significantly improve durability. Since durability remains the most critical and still underexplored aspect of CNC-modified systems, advancing this area will be essential to fully realize the potential of CNCs in next-generation sustainable cement composites.