A Mechanistic Investigation on Cation-Modified Cellulose Nanofibrils-Reinforced Cement Composite

Area of Science:

• Materials Science
• Civil Engineering
• Nanotechnology

Background:

• Cellulose nanofibrils (CNF) are renewable nanomaterials with desirable properties like high strength and hydrophilicity.
• CNF offers advantages over traditional inorganic nanomaterials, including better dispersion, lower cost, and reduced health risks.
• Improving the compatibility of CNF with cementitious materials is crucial for its application in concrete.

Purpose of the Study:

• To enhance the compatibility of cellulose nanofibrils (CNF) with hydrating cement using cationic surfactant modification.
• To evaluate the effects of cation-modified CNF on the mechanical properties, hydration behavior, and crack resistance of cement paste.
• To elucidate the reinforcing mechanisms of cation-modified CNF in cement composites.

Main Methods:

• Cement paste samples were modified with cation-modified CNF.
• Mechanical performance was assessed using compressive and flexural strength tests.
• Hydration heat, restrained ring cracking, microhardness, XRD, and BSE-SEM/EDS analyses were conducted.

Main Results:

• Cation-modified CNF significantly improved the mechanical performance of cement paste, with an optimal dosage of 0.15 wt.%.
• The addition of cation-modified CNF delayed crack initiation in the restrained ring test and increased the early-age hydration rate.
• Microstructural analysis indicated the formation of denser hydration products, suggesting improved microstructure.

Conclusions:

• Cation-modified CNF effectively enhances the mechanical properties and durability of cement composites.
• The optimal dosage for cation-modified CNF in cement is identified as 0.15 wt.%.
• Mechanisms such as internal curing and "short-circuit diffusion" are proposed to explain the observed enhancements.