Abstract
AbstractThe change in demoulding strength of colloidal silica-bonded castables with and without magnesia is investigated with emphasis on the relationship between the demoulding strength and chemical bond changes. It was confirmed that the demoulding strength was raised with the presence of magnesia in colloidal silica-bonded castables because of the increased chemical bonding between the sol particles. The X-ray photoelectron spectroscopy (XPS) and the Fourier transformation infrared spectroscopy (FTIR) results indicate the formation of new Si–O–Mg chemical bond from the decreased O 1s and Si 2p binding energy, and the appearance of weak vibration peaks at 668 and 419 cm−1 in the spectrum of colloidal silica with the addition of MgO after curing at 30°C for 24 hours. The reaction between colloidal silica and magnesia could promote the formation of –Si–O–Mg–O–Si–bonds, which is the primary reason for the demoulding strength improvement.
Highlights
Colloidal silica-bonded castables have advantages over low cement or hydratable alumina-bonded castables in terms of drying performance, sintering properties, lowIn recent years, increasing researches have been done to enhance the green strength of colloidal silica-bonded castables
It has been proposed that magnesium oxide (MgO) addition is favourable to raise the green strength of colloidal silicabonded castables because Si–O–Mg bonds will form from the released Mg2+ ions and the broken Si–O bonds on the surface of silica particles during the placement and curing processes [7, 14]
This work examines the effect of magnesia on demoulding strength of colloidal silica-bonded castables and on the chemical bond formation of silica particles using X-ray photoelectron spectroscopy (XPS) and Fourier transformation infrared spectroscopy (FTIR), with the aim of establishing the relationship between demoulding strength and the change in chemical bonds between SiO2 particles of colloidal silica caused by the presence of magnesia
Summary
Colloidal silica-bonded castables have advantages over low cement or hydratable alumina-bonded castables in terms of drying performance, sintering properties, lowIn recent years, increasing researches have been done to enhance the green strength of colloidal silica-bonded castables. It was confirmed that the demoulding strength was raised with the presence of magnesia in colloidal silica-bonded castables because of the increased chemical bonding between the sol particles.
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