Effect of nano-SiO₂ on the hydration products of C₃S in Portland cement

Abstract

Nano-Silica (NS) modification is a way to enhance the performance of the cement stone. However, the mechanism of NS-modified cement is not clear at low (80 °C) and high (140 °C) temperatures. Therefore, this study focused on tricalcium silicate (C₃S) and the porosity, types and polymerization degree of hydration products with different NS contents with C₃S at 80 and 140 °C were analyzed using ¹H NMR, XRD, SEM, TGA, XPS, and FTIR methods. According to the following results, temperature and initial Ca/Si are the key factors affecting the hydration products of the silicate phase: NS-induced decalcification led to an increase in C-S-H polymerization degree and chain length, but an excessive amount of NS increased the porosity of the hydration product. NS reacted with Ca(OH)₂(CH) and high Ca/Si hydration products, resulting in the formation of structurally dense hydration products with low Ca/Si. However, excessive NS rendered the hydration product unstable and caused high Ca/Si at 80 °C, while it deteriorated Xonotlite with excellent performance at 140 °C, thus affecting the polymerization degree and strength of products.

Keywords:

• Nano-Silica
• tricalcium silicate
• hydration product
• decalcification

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this article.

Data availability statement

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Additional information

Funding

Supported by the following projects: “Study on Deterioration mechanism and control of cement ring in Geothermal Well by injecting supercritical CO₂ into abandoned high temperature gas reservoirs” (Grant Number 2023NSFSC0926) and “Study on the mechanism of improving the corrosion resistance of cement sheath by aluminophosphate cement in CCUS geological storage wells” project (Grant Number 52204014).