Effects of CFB Ash on the Adsorption Mechanism of Polycarboxylate Superplasticiser

Abstract

The effects of circulating fluid bed (CFB) ash on the adsorption performance of polycarboxylate superplasticiser and the mechanism of this influence on the dispersive property of the polycarboxylate superplasticiser were investigated by determing the cement paste fluidity, total organic carbon adsorption, infrared spectroscopic analyses and ζ potential test. The experimental results show that the addition of an inorganic salt into the mixture to change the content of SO₄ ^2- and Fe₂O₃ can improve the adaptability between the CFB ash and polycarboxylate superplasticiser. Adsorption may occur between the polycarboxylate superplasiciser and Fe₂O₃, SO₄ ^2- or other components in CFB ash, leading to a significant reduction in paste fluidity. As the content of Na₂SO₄ in CFB ash reaches 3% or Fe₂O₃ reaches 9%, the paste loses its liquidity. The organic carbon content in the liquor decreases with an increase in Na₂SO₄ or Fe₂O₃ content. Adding some Ba(NO₃)₂ and Na₂S to the liquor can recover the organic carbon content to a certain extent, and the absolute value of ζ potential will increase. The addition of Ba(- NO₃)₂ or Na₂S reduces the adsorption property of Na₂SO₄ or Fe₂O₃ in CFB ash on the polycarboxylate superplasticiser.

Keywords

CFB ash / polycarboxylate superplasticiser / fluidity / TOC adsorption

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