Journal of Advanced Materials and Technologies

Journal of Advanced Materials and Technologies

Study on the Effect of Using a Hybrid Colloidal Silica–Calcium Aluminate Cement Bonding System on the Microstructure and Mechanical Properties of High-Alumina Castables

Document Type : Original Reaearch Article

Authors
Souren Kashkooli 1
Touraj Ebadzadeh 2
Masoud Alizadeh 2
Mahdi Ghasemi Kakroodi 3
1 PhD Student, Department of Ceramic, Materials and Energy Research Center, Karaj, Iran.
2 Professor, Department of Ceramic, Materials and Energy Research Center, Karaj, Iran.
3 Professor, Department of Materials Science and Engineering, University of Tabriz, Tabriz, Iran.
10.30501/jamt.2025.530795.1333
Abstract
With the growing utilization of monolithic refractories, particularly castables, considerable research efforts have been devoted to enhancing their physical, mechanical, and thermomechanical properties. To address the limitations of calcium aluminate cement associated with the formation of low-melting phases, sol–gel bonding systems have been developed as an effective strategy to improve strength and high-temperature performance. In this study, the effect of partially substituting cement with different proportions of colloidal silica in castable formulations was examined. The castables were prepared using conventional processing techniques and sintered at 1500 °C to assess their mechanical performance and microstructural characteristics. Cold crushing strength (CCS) measurements indicated that the composition containing 75% cement and 25% colloidal silica exhibited the highest CCS value of 78 MPa. Phase identification was carried out by X-ray diffraction (XRD), while field-emission scanning electron microscopy coupled with energy-dispersive spectroscopy (FESEM/EDS) revealed a notable reduction in porosity, primarily due to the lower water demand during casting. Additionally, Fourier transform infrared spectroscopy (FTIR) demonstrated the gelation process and the formation of an extensive siloxane (Si–O–Si) network. The combined formation of the calcium aluminate phase and decreased porosity contributed to the improved CCS. However, further increases in colloidal silica content led to a decline in strength, attributed to the reduced contribution of hydraulic bonding from cement.
Keywords
High-Alumina Castable
Low-Cement Castable
Colloidal Silica
Sol-Gel
Subjects
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  • Receive Date 15 July 2025
  • Revise Date 01 August 2025
  • Accept Date 30 September 2025