Mechanical properties of C-S-H globules and interfaces by molecular dynamics simulation

Abstract

At meso-scale, Calcium Silicate Hydrate (C-S-H) can be considered as randomly packed globules (about 4.2nm), which forms the basic unit cell, with water molecules and voids. In this paper, the nanostructures for the globules are developed based on some plausible atomic structures of C-S-H. The mechanical properties for the C-S-H globules are determined through molecular dynamics simulation. Interfaces between the C-S-H globules are also simulated with different amount of water molecules. Key material parameters, e.g., Young's modulus, strength and fracture energy, are obtained. It has been found that longer mean chain length of silicate tends to increase the strength of C-S-H and change the fracture behavior from brittle to ductile failure, in the chain length direction. In the other direction, however, silicate chains do not play an important role while interlayer structure matters. Moreover, pores in the C-S-H nanostructures can considerably reduce the strength of the globule structures in the normal direction to silicate chain but the weakening effect becomes substantially less in silicate chain direction. Further, it has been found that for all types of the interfaces between C-S-H globules, the interface with no extra water molecules has the greatest tensile/shear strength. The mechanical properties obtained in this paper for C-S-H nanostructures and interfaces are necessary inputs to the meso-scale modelling of C-S-H via either granular mechanics, i.e., DEM, or continuum mechanics, i.e., FEM.

Determination of atomistic deformation of tricalcium silicate paste with high‐volume fly ash

“…These effects have also been demonstrated using molecular dynamics simulations. The simulation results revealed that the fracture behavior could be affected by the direction of the silicate chains in C–S–H and that the strength of C–S–H significantly depended on the mean chain length 84 . That is, the smaller and more linear overall deformation behavior of C 3 S‐FA compared with that of pure C 3 S paste was attributed to the increase in the mean chain length of C–S–H owing to the incorporation of HVFA.…”

Interfacial Binding Energy between Calcium-Silicate-Hydrates and Epoxy Resin: A Molecular Dynamics Study

“…It was reported that the interface failure was caused by brittle failure due to the simultaneous separation of epoxy atoms from the matrix, and the tensile strength of the interface was almost unaffected by unloading and reloading before reaching the failure strength. In summary, MD provides a powerful tool for studying the properties of cement materials at the molecular level, which can be used to explain the various properties of the cement paste, mainly the microstructure and mechanical properties, as well as the interface behaviour between the composite models [ 18 , 19 , 20 , 21 ]. However, in a microcapsule-based self-healing system, the factors that influence the interfacial properties of C–S–H/epoxy resins have not been investigated at the molecular scale, which requires the involvement of MD simulation.…”

Effect of Ammonia-Soda Residue on the Strength and Chloride-Resistance Performance of Steel Slag-Granulated Blast Furnace Slag-Based Concrete after Immersion in Artificial Seawater

“…The Ca/Si percentages could reveal the C-S-H gel structure and mechanical properties. With a lower ratio of Ca to Si, the C-S-H gels presented a longer chain structure and better mechanical properties [34,35]. Every Ca/Si of the C-S-H gels in four pastes maintained a certain range.…”