Effect of Nano Seeds in C-S-H Gel Formation: Simulation Study from the Colloidal Point of View

Abstract

The addition of external nanoparticles, mainly nano silica during the hydration of cement is a field of investigation in high performance cements. The added particles act as seeds and initiate early nucleation and subsequent growth of C-S-H gel. Nucleation is triggered very early, before enough clinker grains are dissolved or in other words, before the super saturation condition is attained. Hence, depending on the amount of added seed, the morphology and the mechanical properties of the product differ. Experimental studies in this area are less favored due to economic reasons and simulation studies are rare in the literature. An earlier work by some of the authors introduced a Monte Carlo model which dealt with the kinetics of the hydration process at early ages. The colloidal model incorporated random nucleation in the bulk, followed by an Avramian style layer by layer growth of 5nm sized C-S-H particles. The model was based on a Random Sequential Addition scheme and enabled a satisfactory rationalization of the early growth of C-S-H gel. In the present study, we extend this model for the addition of extra seeds and for different water to cement ratios.

TiO2-SiO2 Coatings with a Low Content of AuNPs for Producing Self-Cleaning Building Materials

“…Regarding the gel time, two factors are key. Firstly, the addition of TiO 2 NPs reduced the gel time due to the TiO 2 NPs acting as seeds, promoting an early nucleation of SiO 2 NPs around TiO 2 species and the subsequent faster gel growth [ 70 ]. Secondly, the increase of gold aqueous dispersion content also produced a significant decrease in the gel time.…”

“…However, the size of SiO 2 particles was significantly different for the materials under study, ranging from 15 to 25 nm for the silica matrix (S0Au). The particle size was reduced as TiO 2 NPs were included in the formulation (10–15 nm for ST0Au) due to the nucleation promoted by TiO 2 [ 70 ]. Thus, in the absence of TiO 2 a larger SiO 2 particle size is required for the nucleation process to begin.…”

Theoretical Elastic Constants of Tobermorite Enhanced with Reduced Graphene Oxide through Hydroxyl vs Epoxy Functionalization: A First-Principles Study

“…The first component is cement taken as the C–S–H gel, which is a typical material in three dimensions. When going down to the nanoscale, cements are first porous and then they can be considered as clusters of nanoparticles that aggregate with several packings to form different types of C–S–H gels, which were measured experimentally by nanoindentation techniques. – The Young’s modulus values for low and high density gels are measured to be around 18 and 30 GPa, respectively. At the atomistic scale, the average Young’s modulus for C–S–H gel-like phases, such as tobermorite and jennite, establishes the upper limits for the best values, which are theoretically and experimentally about 50–60 GPa .…”

Tracing Polymerization in Calcium Silicate Hydrates Using Si Isotopic Fractionation

“…All these points suggest that the isotopic fractionation of silicon isotopes can be used to trace the evolution of cement as temperature increases, by focusing the measurements on the C–S–H gel present. The isotopic fractionation factor depends on the temperature at which the transformation to C2SH occurs, and accordingly, it could be a new tool for studying the loss of cement durability as temperature increases, to add to the tools already available. − The isotopic fractionation factor provides information that is complementary to the data provided by standard tools, allowing the nuclear magnetic resonance measurements that are often used to study C–S–H gels to be better understood. , Besides, the isotopic fractionation properties of the C–S–H gels, with or without substitutions of Ca 2+ by H + , are significantly different. At 300 K, the α 30 Si CSHgel–CSHgel(H) is equal to −1.9% and can be used to trace calcium leaching of C–S–H gels, which is an additional cause of cement strength deterioration.…”