Effect of Ca:Si Ratio on the Tensile Behavior of CNT‐Reinforced Calcium Silicate Hydrate: A Molecular Dynamics Approach

ABSTRACT Understanding the mechanical properties and failure mechanisms at nano and molecular levels are crucial to develop novel nano‐modified cementitious composites. In this study, Molecular Dynamics (MD) models, which were useful in understanding molecular/ nano level behavior of materials, were created using single and multi‐walled armchair, zig‐zag Carbon Nanotubes (CNT) with different diameters embedded in Calcium Silicate Hydrate (C–S–H) with varying calcium‐to‐silicon (Ca:Si) ratios. MD simulations were carried out with different loading directions and different orientations of CNT to understand directional effects on tensile stress‐strain behavior. CNT reinforced C–S–H showed an anisotropic behavior which mainly relies on Ca:Si ratio, and alignments between loading direction, CNT orientation, and silicate layers of C–S–H. The improvement of tensile properties such as elastic modulus and tensile strength of CNT reinforced C–S–H was observed when CNT orientation and loading direction aligned. Multi‐walled CNT reinforced C–S–H was found to have better tensile performance compared to Single‐walled CNT. Tensile stress‐strain behavior and fracture mechanisms of the composite are explained using molecular structure of C–S–H, bonding between CNT and C–S–H and molecular‐level bond failures. The fracture behavior of CNT reinforced C–S–H under tensile loading was observed to closely resemble the macro mechanical behavior of fiber reinforced concrete.