The activation of fluorgypsum with slag activator and the fluorine solidification mechanics

Abstract

The mechanism of activator to fluorgypsum and the fluorine solidification were investigated by the performances of composite binding material. Through the setting time testing of fluorgypsum with NaOH, Na₂SO₄ and NaF, the least activator dosage were all 1%. And the cementitious material over 80% of fluorgypsum was processed to improve its quality with slag, fly ash and clinker. The maximum compressive strength of composite binding material was over 12.90 MPa in 28 days, and the concentration of fluroride reduced 64.7% which compared with the pure fluorgypsum binding material. Analysis of X-ray diffraction and scanning electron microscopy images showed that ettringite crystals, dihydrate gypsum crystals and C-S-H gel were filled with each other. The unreacted CaF₂ crystals were embedded by a great deal of network and filamentous C-S-H gel. It was the main reason that the composite binding material strength improved, water resistance increased and leaching toxicity reduced.

Keywords

fluorgypsum / activation / slag / fluorine solidification

References

[1] Bian Guihua. New Progress of Mechanism Research on Influence of Fluoride to Human Body Health[J]. Chemical Production and Technology, 2008(5): 13–16

[2] Yuan Runzhang. Cementitious Material Science[M], 1996 Wuhan Wuhan University of Technology Press

[3] Yan Peiyu, You Yi. Research of Binder with Fluorgypsum and Fly Ash[J]. New Building Materials, 1998(6): 28–30

[4] Yan Peiyu, You Yi. Hydraulic Properties of the Binder Consisting of Fluorgypsum and Fly Ash under Different Curing Conditions[J]. Journal of the Chinese Ceramic Society, 1998(6): 689–694

[5] Yan P., You Y. Studies on the Binder of Fly Ash-fluorgypsum-Cement[J]. Cement and Concrete Research, 1998, 28(1): 135-140.

[6] Zhou Wanliang, Long Jinghua, Zhan Binggen. Further Study on Property of Fly Ash-Fluorogypsum-Cement Composite Binder[J]. Journal of Building Materials, 2008(4): 179–182

[7] Wang Jiarong, Liu Jiaxiang. Research on the Preparation of Binding Material and Concrete by Fluorogypsum and Fly Ash[J]. Multipurpose Utilization of Mineral Resources,2009(6): 38–41

[8] Fraire Luna P E, Escalnate Graica J I, Gorokhovsky A. Mechanical Properties and Reaction Products in the Ternary Hydraulic System Anhydrite-Blast Furnace Slag-Metakaolin[C]. 2005 International Congress — Global Construction: Ultimate Concrete Opportunities, United Kingdom, 2005

[9] Fraire Luna P. E., Escalnate Graica J. I., Gorokhovsky A. Composite Systems Fluorgypsum-blastfurnance Slag-metakaolin, Strength and Microstructures[J]. Cement and Concrete Research, 2006, 36(6): 1 048-1 055.

[10] Martine Aguilar O. A., Castro Borges P., Escalante Garcia J. I. Hydraulic Binders of FluorgypsumPortland-Cement and Blast Furnace Slag, Stability and Mechanical Properties[J]. Construction and Building Materials, 2010, 24(5): 631-639.

[11] Peng J., Zhang J., Bai Leng. Hydration and Hardening Characteristics of Anhydrite Binder Modified with Slag[J]. Journal of Tongji University(Natural Science), 2009, 959: 934-937.

[12] Peng Jiahui, Zhang Jianxin, Bai Leng. Study on Anhydrite Binder Activated by Sulfate Salt and Modified with Slag[J]. Bulletin of the Chinese Ceramic Society, 2008 (4): 837–842

[13] Yan P., Yang W., Qin X., . Microstructure and Properties of the Binder of Fly Ash-fluorogypsum-Portland Cement[J]. Cement and Concrete Research, 1999, 29(3): 349-354.