Interactions between fluoride ions and cement paste containing superplasticizer

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• 作者：Kazuki Matsuzawa^a ; ^{matsuzawa.k.aa@m.titech.ac.jp} ; Daiki Atarashi^b ; Masahiro Miyauchi^c ; Etsuo Sakai^c
• 关键词：Cement paste (D) ; High-range water reducers (D) ; Dispersion (A) ; Cement manufacture (E) ; Fluoride (D)
• 刊名：Cement and Concrete Research
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：91
• 期：Complete
• 页码：33-38
• 全文大小：592 K
• 卷排序：91

文摘

Fluoride compounds are used as fluxes in the low-temperature calcination of cement. Elution of fluoride ions after calcination decreases the fluidity of cement paste containing superplasticizers, but the mechanism of fluidity decrease is unclear. Authors investigated the effects of fluoride on cement pastes containing superplasticizers and the fluidity decrease mechanism. KF addition to cement paste containing a polycarboxylate- or naphthalenesulfonate-based superplasticizer increased the yield stress, the amount of adsorbed superplasticizer, and the solid-phase specific surface area. KF addition increased the amount of adsorbed superplasticizer for alite paste but not for Ca3Al2O6-CaSO4 paste. Transmission electron microscopy found SiO2 fine particles after KF addition. In the absence of water, the increase in specific surface area with fluoride was larger in hydrated than in unhydrated cement. It is supposed that the fluidity decrease results from the preferential adsorption of superplasticizer on SiO2 particles generated by reactions between hydrated calcium silicate and fluoride ions.