Interactions between fluoride ions and cement paste containing superplasticizer

Journal Article · Sun Jan 15 04:00:00 EST 2017 · Cement and Concrete Research

DOI:https://doi.org/10.1016/J.CEMCONRES.2016.10.006· OSTI ID:22697092

Matsuzawa, Kazuki ^[1]; Atarashi, Daiki ^[2]; Miyauchi, Masahiro; Sakai, Etsuo ^[3]

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1. Tokyo Institute of Technology, Graduate School of Science and Engineering, 2-12-1 Ookayama Meguro-ku, Tokyo (Japan)
2. Shimane University, Department of Chemistry, Interdisciplinary Graduate School of Science and Engineering, 1060 Nishikawatsu, Matsue, Shimane (Japan)
3. Tokyo Institute of Technology, School of Materials and Chemical Technology, 2-12-1 Ookayama Meguro-ku, Tokyo (Japan)

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 Ca{sub 3}Al{sub 2}O{sub 6}-CaSO{sub 4} paste. Transmission electron microscopy found SiO{sub 2} 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 SiO{sub 2} particles generated by reactions between hydrated calcium silicate and fluoride ions.

• OSTI ID: 22697092
• Journal Information: Cement and Concrete Research, Journal Name: Cement and Concrete Research Vol. 91; ISSN 0008-8846; ISSN CCNRAI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ADSORPTION
ALUMINIUM OXIDES
CALCIUM SILICATES
CALCIUM SULFATES
CEMENTS
FINE PARTICLES
IONS
PLASTICIZERS
SILICA
SILICON OXIDES
SPECIFIC SURFACE AREA
SULFONATES
TEMPERATURE RANGE 0065-0273 K
TRANSMISSION ELECTRON MICROSCOPY
WATER