Computational modeling of shear deformation and failure of nanoscale hydrated calcium silicate hydrate in cement paste: Calcium silicate hydrate Jennite

Abstract

Calcium silicate hydrate Jennite is a molecular structure commonly accepted as a representation of the complex calcium silicate hydrate gel formed during the hydration of typical Portland cement. In this paper, the behavior of nanoscale calcium silicate hydrate Jennite under shear deformation was investigated using molecular dynamics simulations. Computational samples representing the nanoscale structure of calcium silicate hydrate Jennite were subjected to shear deformation in order to investigate not only their mechanical properties but also their deformation behavior. The simulation results indicated that the nanoscale calcium silicate hydrate Jennite under shear deformation displays a linear elastic behavior up to shear stress of approximately 1.0 GPa, and shear deformation of about 0.08 radians, after which point yielding and plastic deformation occurs. The shear modulus determined from the simulations was 11.2 ± 0.7 GPa. The deformation-induced displacements in molecular structures were analyzed dividing the system in regions representing calcium oxide layers. The displacement/deformation of the layers of calcium oxide forming the structure of nanoscale calcium silicate hydrate Jennite was analyzed. The non-linear stress–strain behavior in the molecular structure was attributed to a non-linear increase in the displacement due to sliding of the calcium oxide layers on top of each other with higher shearing. These results support the idea that by controlling the chemical reactions, the tailored morphologies can be used to increase the interlinking between the calcium oxide layers, thus minimizing the shearing of the layers and leading to molecular structures that can withstand larger deformation and have improved failure behavior.

Computational Modeling of Multi-Scale Features in Cementitious Materials

“…Brief discussions of key results from shear deformation and failure of nanoscale CSH Jennite are presented next. Complete details are available in reference [8].…”

“…Based on the structural characteristics of nanoscale CSH Jennite illustrated above, results from mechanical behavior of the material under shear deformation and the changes produced by the deformation applied on the calcium oxide layers are briefly illustrated. Complete details of MD modeling methodology and shear deformation of nanoscale CSH Jennite are available in reference [8]. Figure 3 presents the shear stress-shear strain behavior obtained from shear deformation of nanoscale CSH Jennite built upon 64 unit cells.…”

“…This correlates well with the transition from linear to non-linear behavior of the stress-strain plot shown in Figure 3 (left). Complete discussions are presented in reference [8].…”

“…Molecular structure of nanoscale CSH Jennite viewed across the crystallographic plane. Arrows indicate the direction of the shear stress simulated[8].…”

Constitutive Stiffness Characteristics of Cement Paste as a Multiphase Composite System—A Molecular Dynamics-Based Model

“…Present work thus focused on two-phase systems of cement paste, consisting of CSH as the main hydrated phase, in combination with unhydrated phases C 3 S and C 2 S. Modeling nanoscale CSH features presents two big challenges due to the complex nature of the molecular CSH structure, namely: (i) it is a poor crystalline material, and (ii) different molecular representations of CSH phases can be considered. However, in mature cement paste with sufficient hydration, most of the CSH phase has been considered to be analogous to the crystalline mineral jennite [36,37]. Therefore, the molecular structure of mineral jennite is also followed in this present study to represent the CSH phase.…”