Hydration kinetics and mechanism of cement pastes with PEGylated cellulose nanocrystals

The low water-to-cement ratio cement-based materials represented by high-performance or ultra-high-performance concrete exhibit excellent mechanical and durability properties but suffer from poor flowability and insufficient and nonuniform hydration. Polyethylene glycol-grafted cellulose nanocrystal (PCNC) was synthesized by grafting polyethylene glycol (PEG) onto cellulose nanocrystal (CNC) and then was incorporated into cement paste to improve its flowability and hydration performance. A series of tests were conducted to analyze the flowability, compressive strength, and hydration behavior of cement paste with PCNC, with the hydration mechanism revealed. The results show that PCNC promotes more complete and uniform cement hydration through mechanisms including short-circuit diffusion, nucleation, and steric hindrance, resulting in improved flowability and compressive strength compared to pure and CNC-modified cement paste. The optimal PCNC dosage is 0.1 %, where the flowability and 28-day compressive strength increased by 10.73 % and 30.63 %, respectively. Finally, a mechanism model by which PCNC improves cement hydration was proposed.