Atomic Interactions Solidified Through the Introduction of Cellulose Nanocrystals to Cementitious Matrix: a Theoretical Study at the Molecular Level

Abstract

Cellulose nanocrystals (CNCs) have been proven to be an effective additive to the cementitious mixes, reforming the pore structure and boosting the hydration process, significantly boosting the mechanical properties of the hardened product. Although experimental works have explored the changes to the morphology and engineering properties of the CNC-modified cementitious mixtures, the mechanisms involved in the microscale remain mostly elusive. Moreover, the information on the benefits of the CNC during and after the curing process are severely lacking. Here, we present a detailed investigation of the CNC within the curing and cured cementitious matrix, modeled by calcium silicate hydrate (CSH), and explored through the analytical tools of molecular dynamics conducted in COMPASS forcefield. The results show a significant difference in molecular mobility between the two stages, which is also the case for the CNC-CSH interactions. This interaction is strong enough both during and after curing to force the failure through stacked CNCs instead of the CSH-CNC-CSH bonds. Moreover, we show that pairing CNC with carbon nanomaterials, here represented by carbon nanotubes (CNTs), can significantly boost the durability of composite by binding the metal cations native to the cementitious matrix. The results from this study can help form a better understanding of the effects of CNC during and after the curing process, while presenting new paths for continued research in this area through depicting blueprints for microscale investigations within the cementitious matrix.