Effect of Water on the Dynamic Tensile Mechanical Properties of Calcium Silicate Hydrate: Based on Molecular Dynamics Simulation

Jikai Zhou,Yuanzhi Liang

doi:10.3390/ma12172837

Abstract

To study the effect of water on the dynamic mechanical properties of calcium silicate hydrate (C–S–H) at the atomic scale, the molecular dynamics simulations were performed in uniaxial tension with different strain rates for C–S–H with a degree of saturation from 0% to 100%. Our calculations demonstrate that the dynamic tensile mechanical properties of C–S–H decrease with increasing water content and increase with increasing strain rates. With an increase in the degree of saturation, the strain rate sensitivity of C–S–H tends to increase. According to Morse potential function, the tensile stress-strain relationship curves of C–S–H are decomposed and fitted, and the dynamic tensile constitutive relationship of C–S–H considering the effect of water content is proposed. This reveals the strain rate effect of the cementitious materials with different water content from molecular insights, and the dynamic constitutive relationship obtained in this paper is necessary to the modelling of cementitious materials at the meso-scale.

Highlights

Strong dynamic loadings, such as earthquake, explosion, impact, strong winds, and typhoons, etc. cause immeasurable losses for major cementitious structures
H under a high strain rate (0.8 ps ) and low strain rate (0.0008 ps−1). It shows that (1) For the configurations of calcium silicate hydrate (C–S–H) in the failure stage, the destruction of dry C–S–H occurs in interlayer calcium configurations of C–S–H in the failure stage, the destruction of dry C–S–H occurs in interlayer layer, so the interlayer calcium layer is the weak layer of totally dry C–S–H and the saturated C–S–H
(2) The residual peak tensile strength of C–S–H matrix weakened by water molecules is equal to the peak tensile strength of totally dry C–S–H subtracting the initial stress(σSr ) due to initial strain in the tensile stress-strain relationship curve of totally dry C–S–H after water absorption; (3) The peak tensile strain of C–S–H matrix decomposed by C–S–H composite with different degree of saturation is consistent with that of a totally dry C–S–H matrix; (4) The stress of C–S–H matrix with different degree of saturation is obtained by multiplying the stress of absolutely dry C–S–H matrix by the reduction coefficient (η), calculated by the following formula: σS

Summary

Introduction

Strong dynamic loadings, such as earthquake, explosion, impact, strong winds, and typhoons, etc. cause immeasurable losses for major cementitious structures. The improvement of dynamic mechanical properties is very important to prevent dynamic catastrophe of major projects, and many efforts have been dedicated to it [1,2,3,4,5,6]. Rossi et al [8], Reinhardt et al [9], Cadoni et al [10], and Ross et al [11] discovered that the dynamic strength of concrete increased for hydrated concrete under different strain rates, and dry concrete was insensitive to the strain rate. Wu et al [13] explored the effect of strain rates and water content on the mechanical behavior of concrete, and the results revealed that flexural strength increased with an increase in strain rates, while increasing water content would lower the flexural strength

Methods

Results

Conclusion