The kinetic of calcium silicate hydrate formation from silica and calcium hydroxide nanoparticles

JOURNAL OF COLLOID AND INTERFACE SCIENCE

卷:605

Article

Camerini, Rachel^1,2  Poggi, Giovanna^1,2  Ridi, Francesca^1,2  Baglioni, Piero² 

[1] Univ Florence, Dept Chem, Via Lastruccia 3, I-50019 Sesto Fiorentino, FI, Italy

[2] Univ Florence, CSGI, Via Lastruccia 3, I-50019 Sesto Fiorentino, FI, Italy

关键词: Calcium silicate hydrate;    Silica nanoparticles;    Calcium hydroxide nanoparticles;    Hydroxypropyl cellulose;    Hydration kinetics;    Boundary nucleation and growth model;    Diffusion model;   

DOI  :  10.1016/j.jcis.2021.06.168

来源: Elsevier

【 摘 要 】

Hypothesis: The mechanism of calcium silicate hydrate (CSH) formation, a relevant component of cement, the largest used material by mankind, is well documented. However, the effects of nano-sized materials on the CSH formation have not yet been evaluated. To this aim, a kinetic study on CSH formation via the pozzolanic reaction of nanosilica and calcium hydroxide nanoparticles, and in the presence of hydroxypropyl cellulose (HPC) as hydration regulator, is reported in this paper. Experiments: The reagents were mixed with water and cured at 10, 20, 30 and 40 degrees C. The reaction kinetics was studied with differential scanning calorimetry (DSC). A Boundary Nucleation and Growth model (BNGM) combined with a diffusion-limited model was used to analyze the data, yielding induction times, reaction rates, activation energies, nucleation and linear growth rates, and the related diffusion coefficients. Findings: The rate constants k(B) and k(G), which are, respectively, the rate at which the nucleated boundary area transforms, and the rate at which the non-nucleated grains between the boundaries transform, increase with temperature. Their different temperature dependence accounts for the prevailing effect of nucleation over nuclei growth at progressively lower temperatures. The nucleation rate, I-B, is strongly enhanced when using nanomaterials, while the linear growth rate, G, is limited by the tightly packed structure of the transforming matrix. HPC influences the kinetics between 10 and 30 degrees C; at 40 degrees C the temperature effect becomes predominant. HPC delays induction and acceleration periods, increases E-a(k(B)), and enhances the reaction efficiency during the diffusion regime, by retaining and delivering water over the matrix, thus allowing a higher water consumption in the hydration reaction of CSH. (C) 2021 Elsevier Inc. All rights reserved.

【 授权许可】

Free