Structural models of random packing of spheres extended to bricks: Simulation of the nanoporous calcium silicate hydrates

Abstract

Structure simulation algorithms of random packing of spheres and bricks have been developed. These algorithms were used to reproduce the nanostructure of the cementitious calcium silicate hydrates. The textural parameters (specific surface area, porosity, pore size, etc.) of a calcium silicate hydrates (C-S-H) sample, the main binding phase of hydrated cements, have been derived from N2-physisorption experiments. At the same time, these parameters have been simulated by using a sphere-based structural model, where the spheres are randomly packed according to several hierarchical levels. The corresponding algorithm has been extended for managing cuboids instead of spheres. The C-S-H sample density is successfully predicted by considering the presence of water in pores defined by the sphere network within 10-nm-size globules and assuming a tobermorite-like skeleton. Simulations with bricks (321.4nm3) yield also textural parameters that are consistent with N2-physisorption data, but with a globule radius (22nm) twice as big as that obtained when using spheres.