Hydration kinetics and mechanism of C3S with cellulose nanocrystals

Tricalcium silicate (C 3 S) is the primary ingredient in ordinary Portland cement (OPC). Understanding the hydration kinetics of C 3 S with cellulose nanocrystals (CNC) is the key to unveiling the intrinsic mechanism of CNC affecting OPC hydration . This study investigates the hydration interactions between C 3 S and CNC through extensive testing. Findings indicate that CNC incorporation can initially slow the hydration reaction and postpone the early-stage hydration of C 3 S. However, past the initial period (3 days in this study), CNC presence enhances the hydration pace and aids the hydration process , leading to an increase in the formation of calcium silicate hydrate (C–S–H) and calcium hydroxide (CH) without creating new phases. Further, the presence of CNC promotes the homogenous hydration of C 3 S, ensuring a homogenous distribution of hydration products . It also reduces the Ca/Si ratio in the C–S–H, without altering the C–S–H morphology. A correlation is made between heat flow and the thickness of hydration products enveloping C 3 S particles, confirming that CNC can intensify the inward water diffusion rate through C 3 S particles for the same hydration product thickness. Critically, it is found that the effect of CNC on C 3 S hydration is dependent on the water/C 3 S ratio. A low or moderate water/C 3 S ratio can promote C 3 S hydration but a very high water/C 3 S ratio diminishes the beneficial effects of CNC on C 3 S hydration. Finally, the study proposes a explanation for CNC's influence over the hydration of C 3 S with varying water/C 3 S ratios.