A cascade micromechanical model for mechanical properties of multiphase CNC/C-S-H nanocomposites

Cellulose nanocrystal (CNC) has emerged as a reinforcement for calcium silicate hydrate (C-S-H), the primary binding phase of cement-based materials, creating C-S-H nanocomposites demonstrating desired mechanical properties. However, predicting the mechanical properties of CNC/C-S-H nanocomposites is challenging, due to their complex microstructural and chemical characteristics. This paper presents a cascade micromechanical model that considers CNC-water association, interphase effects to predict the effective mechanical properties of CNC/C-S-H nanocomposites. The hierarchical recursive principle is integrated to analyze the connectivity of the microstructural characteristics of CNC/C-S-H nanocomposites. The model predictions are consistent with experimental results. The effects of CNC dosage, water adsorption, cascade level, CNC-water hybrid phase, and CNC-water/C-S-H interphase on the mechanical properties of CNC/C-S-H nanocomposites are also investigated. The results reveal that CNC-water/C-S-H interphase plays dominant roles in different mechanical properties, and water adsorption introduces competing effects of hydration promotion and stiffness reduction. The proposed framework provides a physics-based and computationally efficient tool for predicting and optimizing the mechanical properties of CNC/C-S-H nanocomposites, with potential applications in the design of advanced C-S-H-based materials.