A Molecular Dynamics Study on the Structure, Interfaces, Mechanical Properties, and Mechanisms of a Calcium Silicate Hydrate/2D-Silica Nanocomposite

Abstract

The incorporation of nano-reinforcements is believed to be a promising method to create high performance nanocomposites, which are largely dependent on the interfacial connections. In this work, the newly emerging two-dimensional (2D) material, 2Dsilica is intentionally intercalated into the interlayer defective sites of calcium silicate hydrate (C-S-H), which is the primary hydration product of ordinary portland cements. The reactive molecular simulation results indicate the nano-reinforcement can strongly interact with the inorganic matrix to form a high-ductility nanocomposite. The uniaxial tensile loading tests show the plastic stage of the C-S-H is considerably enhanced due to the intercalation of 2D-silica, which removes the intrinsic brittleness of cementbased materials at the nano-scale. It is observed that the dangling atoms at the edge of 2D-silica can react with non-bridging oxygen atoms of C-S-H, forming Si-O-Si bonds at interfaces. Those covalent bonds transform Q 1 and Q 2 in the C-S-H into high connectivity Q 3 and Q 4 species, which increases the integrity of the matrix and its resistance to crack propagation. During the tensile process, the elongation and breakage of those high-strength covalent bonds needs higher tensile stress and consumes higher energy, which leads to a strong plasticity and higher toughness. This work may shed new lights on the interaction mechanisms between 2D-materials and inorganic hosts, and provide solutions to modifying the brittleness of concrete.

Study on Interfacial Interaction of Cement-Based Nanocomposite by Molecular Dynamic Analysis and an RVE Approach

“…A molecular dynamic analysis needs to be performed to understand the atom level interaction to determine the mechanical and electrical properties. It is possible to do a molecular dynamics simulation if the structure is frst optimized for energy which followed by geometric optimization [22]. Te molecular dynamics study is performed using the FORCITE module in the material studio.…”

Two-Dimensional Ultrathin Silica Films

“…Composite 2D-silica systems have the potential to become important in nanotechnology. , As we know from the discussions in section , a silica monolayer is bound to a metal support through Si–O–metal linkages. In contrast, silica bilayers are weakly bound to the support via dispersive forces.…”

Perspective/Discussion on “Quantum Mechanical Metric for Internal Cohesion in Cement Crystals” by C. C. Dharmawardhana, A. Misra and Wai-Yim Ching

“…In contrast to other group (c) crystals that have both Q2 and Q0, Suolunites mainly contain Q1 Si-tetrahedra. In this group, Suolunites (c.2) are the crystals that contain molecules of water and are the only naturally occurring C-S-H crystals to have H 2 O: Si 2 O: CaO ratios of 1:1:1 [8,10]. In Suolunites (c.2), all water molecules have regular covalent bond lengths of 1.00333 Å.…”

“…Regarding the position of 'H', the uncertainties were previously explained in a study of four crystalline C-S-H crystals [10]. HBs play vital roles in the behaviors of these substances because they have an important presence in C-S-H. Generally, these facts have been acknowledged but rarely quantitatively researched.…”