Effects of particle size of colloidal nanosilica on hydration of Portland cement at early age

Abstract

The aim of this study is to evaluate the effects of different particle sizes colloidal nanosilica (30, 60, and 140 nm) on the early performance of Portland cement. Flowability, mechanical property, and microstructural characterization tests were conducted to investigate the macroscopic and microscopic properties. The results revealed that the flowability of the paste decreased with the reduction of the particle size of colloidal nanosilica. The main reason was that the sol may form flocculation restricting a part of free water under ion environment, and this phenomenon became more serious as the particle size decreased. The compressive strength with 60-nm sol was higher than that of the other two, and hydration activities under different situations were further proved by hydration heat analysis. The reasons causing this result were mainly because flocculation limited the original chemical activity like pozzolanic and seeding effects of nanomaterials. Through thermogravimetric analysis and X-ray diffraction, it can be concluded that the seeding and pozzolanic effects of nanomaterials dominated the hydration process at different periods. Comparing images from scanning electron microscopy, the microstructure was most compact when incorporated into 60-nm sol, and filling effects also contributed to the performance during hardening.

The effects of seawater and nanosilica on the performance of blended cements and composites

“…On the other hand, NS addition lead to important changes from a rheological point of view: the yield-stress increased by a factor of about 2.5 in the presence of tapwater and by a factor of about 4 with seawater. Similar changes have been observed experimentally and attributed to the extremely high surface area of NS, with the higher water demand of nanoparticles thus resulting in a reduction of the fluidity of specimens (Flores et al 2017;Zhang et al 2019). Furthermore, the higher the applied shear-rate, the lower the difference between curves with and without NS, with plastic viscosities then being expected to be in the same order of magnitude.…”

“…It can be clearly seen that specimens containing NS generally exhibited lower CH contents at all tested ages. This phenomena can be attributed to the remarkable pozzolanic activity of NS, which results in reaction of NS with the available CH and the production of more calcium silicate hydrate (C-S-H) gel (Zhang et al 2019).…”

Influence of Nanosilica on Mechanical Properties, Sorptivity, and Microstructure of Lightweight Concrete

“…In the case of the hardened properties of LWAC, it was observed that even small NS dosages (1 wt.%) were beneficial in improving overall concrete performance, with increments in NS content leading to considerable improvements. The beneficial effect of NS on strength development can be attributed to the nano-filling and nucleating effects, as well as to the pozzolanic activity of silica nanoparticles, which results in an acceleration of cement hydration, the production of a higher amount of dense calcium–silicate–hydrate (C-S-H) phase, a refinement in microstructure, and an improvement in the interfacial transition zone (ITZ) between the cement matrix and the aggregate [35,36,37,38,39]. As a result, the strength development process is accelerated from the early hours of hydration, together with an improvement in long-term mechanical properties [40,41,42,43].…”

Nanoparticle-reinforced building materials with applications in civil engineering

“…The particle size of colloidal nanosilica has great influence on hydration of Portland cement. The paper titled ''Effects of particle size of colloidal nanosilica on hydration of Portland cement at early age'' is authored by Zhang et al 24 They conducted a series of experiments including flowability, mechanical properties, and microstructural characterization tests to study the macroscopic and microscopic properties of cement paste containing different particle sizes of colloidal nanosilica. Their experiment results indicated that flowability of the paste decreased with the decrease of colloidal nanosilica particle size, because more sol formed flocculation restricting more free water under ion environment.…”