Dispersion of cellulose nanocrystals and cellulose nanofibers in aqueous suspensions: synergistic effect of concrete superplasticizers

Achieving optimal dispersion of cellulose nanomaterials (CNMs) is crucial for unlocking their potential to enhance the performance of cement-based materials. This study investigates the synergistic effects of concrete superplasticizers (SPs) in dispersing CNMs within aqueous suspensions. The CNMs examined include cellulose nanocrystals (CNC) and cellulose nanofibers (CNF), each paired with one of three different SPs: polycarboxylate ether (PCE), linear polycarboxylate (PCL), and polynaphtalene sulfonates (PNS). The study primarily evaluated the apparent viscosity (η_app) and storage modulus (G′) to assess dispersion effectiveness. Mechanical stirring proved effective in preparing clean, accessible hydroxyl groups (OH⁻) on the CNMs for chemical modification. Depending on the type of CNMs, mechanical stirring induced distinct rheological behaviors that influenced their dispersion. Moreover, SPs successfully dispersed the investigated CNMs. The surface charge of CNMs governed the adsorption of SPs, which was influenced by the chemical structure of the SPs. Additionally, the aspect ratio of CNMs affected the effectiveness of steric hindrance or electrostatic repulsion in achieving proper dispersion. The findings provide valuable insights and recommendations for dispersing CNMs using concrete SPs.