Influence of spherical pore on nanoindentation response in calcium silicate hydrate: a molecular dynamics study

Calcium silicate hydrate (C-S-H) gel, as an important component of cement, is a kind of porous material with random distribution of moist or arid pores. As a prominent experimental method for circumventing cracks in cement-based materials, nanoindentation has rarely been employed in the numerical simulation for describing the localized morphing mechanism of C-S-H gel, and few studies have shown the nexus between nanoindentation and porous properties. In this paper, molecular dynamics (MD) would be utilized to simulate the nanoindentation process of C-S-H gel materials within spherical pores, and to focus on examining the factors such as pore distribution, pore radius, indentation depth, and pore water. Results show that due to the supporting force provided by aperture wall, appropriate pore location and size might increase the indentation modulus. In arid porous materials, indentation modulus is proportional to the hardness in the (0,0,1) orientation, which could be applied to estimate the modulus in this orientation of non-porous models during the ultra-deep nanoindentation, but the proportionality would failure as introducing water to the pore. Maintaining a moisture content of approximately 80 % could efficiently obtain an elastic modulus of solid C-S-H in quasi-elastic stage. These conclusions strengthen the cognition about mechanism of pores in hydrated calcium silicate, which is conducive to establish a numerical model of porous C-S-H gel and further furnish the conception of high-performance porous calcium silicate hydrate with tutelage. • MD Simulation of nanoindentation for C-S-H within one arid or moist pore. • Relationship between the hardness and indentation modulus. • Super-deep nanoindentation for modulus prediction. • Relationship between pore properties and mechanical response. • Deformation mechanism of the surface and pore in nanoindentation.