Crystalline phase formation in metakaolinite geopolymers activated with NaOH and sodium silicate

Zhang, Bo; MacKenzie, Kenneth J.D.; Brown, I. W. M.

doi:10.1007/s10853-009-3715-1

Cited by 91 publications

(46 citation statements)

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“…In the MS-based geopolymers, the major crystalline phases after curing were hydrated zeolite A (PDF # 00-039-0222) and a hydrosodalite of intermediate water content, Na 6 (AlSiO 4 ) 6 Á4H 2 O (PDF # 00-042-0216). This hydrosodalite was also identified by Hajimohammadi et al [13] and Zhang et al [24] in geopolymers (one-part and metakaolin-based, respectively) of comparatively low starting SiO 2 /Al 2 O 3 ratio. The latter authors determined the average size of the hydrosodalite crystallites in their samples to be ca.…”

Section: Xrd and Nmr Analysessupporting

confidence: 72%

“…SiO 4 tetrahedra linked to four AlO 4 , which are structural units of zeolites [27,28] as Si MAS NMR spectra of the silica MS, the MS-based geopolymers cured for 1 day and the insoluble residue (HCl ? 1000°C) of the MS-based geopolymer with a starting ratio SiO 2 /Al 2 O 3 & 6 cured for 1 day well as of geopolymers with comparatively low SiO 2 / Al 2 O 3 ratio [15,24,29]. Smaller amounts of Si(3Al) units (SiO 4 tetrahedra having bridging oxygens to three AlO 4 and one SiO 4 unit), possibly present in the amorphous geopolymeric gel, may also contribute to the signals from -80 to -92 ppm.…”

Section: Degree Of Reaction (Dissolution Method)mentioning

confidence: 99%

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Degree of reaction and phase content of silica-based one-part geopolymers investigated using chemical and NMR spectroscopic methods

et al. 2015

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One-part geopolymers were synthesized from two different silica materials (a silica-rich residue from chlorosilane production and a commercial microsilica) and sodium aluminate at three different SiO 2 /Al 2 O 3 ratios and a nominal water/solids ratio of 0.5. The degree of reaction of the silica in the cured geopolymers (i.e. the fraction of silica dissolved to form aluminosilicates and minor products) was determined using two different methods: chemical attack with HCl to dissolve the reaction products and evaluation of peak areas of 29 Si MAS NMR spectra. It was found that the degree of reaction of the silica decreases with increasing the silica content of the starting mix, and that it is almost constant after 1 day of curing and almost independent from the kind of starting silica. From the results of the NMR-based method, the mean SiO 2 /Al 2 O 3 ratio of the reaction products (aluminosilicates and minor products) can be estimated to be ca. 2.0, nearly independent of the starting composition of the geopolymers. The dissolution method is biased, but of sufficient precision to be useful for following changes of the degree of reaction. Major crystalline phases in the cured geopolymers are zeolite A and/or hydrosodalite. Depending on the starting composition, the relative amounts of these zeolites vary; additionally, sodalite (only for the residue from chlorosilane production with [1 wt% Cl -), faujasite, and zeolite EMT can appear in the geopolymers. The 29 Si and 27 Al MAS NMR results indicate mainly Si(4Al) and Al(4Si) sites, in line with the presence of zeolite A, hydrosodalite, sodalite, and geopolymeric gel of comparatively low SiO 2 /Al 2 O 3 ratio.

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Section: Xrd and Nmr Analysessupporting

confidence: 72%

Section: Degree Of Reaction (Dissolution Method)mentioning

confidence: 99%

Degree of reaction and phase content of silica-based one-part geopolymers investigated using chemical and NMR spectroscopic methods

et al. 2015

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“…The maximum compressive strength recorded was 31.33 MPa (GWG12) at 7th days. The addition of water glass to NaOH solution lead to additional of soluble silicate (SiO2) and alkali (Na2O content) to the system which resulted in an increase of SiO2/Na2O oxide in the alkaline activator thus increasing the geopolymerisation process [12]. Since, the water glass accelerate the geopolymerisation process, the strength and physical properties of hardened geopolymer also enhanced.…”

Section: Figure 1 Compressive Strength Of Geopolymer Samples Activatmentioning

confidence: 99%

Comparative study on early strength of sodium hydroxide (NaOH) activated fly ash based geopolymer

Yahya

Talib

Razak

2017

AIP Conference Proceedings

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Abstract. The urge to reduce carbon dioxide (CO2) emission has encourage researchers to introduce environmental friendly binder or known as geopolymer. This new binder was produced by mixing source materials rich in silica and alumina with alkaline liquids. For this study, class F fly ash was used as source material with two different types of alkaline activator; sodium hydroxide (NaOH) only and a combination of water glass with NaOH. The different concentration of the NaOH solutions (8M, 10M, 12M and 14M) is used in the production of geopolymer. The parameters such as curing regime, solid/liquid ratio, and water glass/NaOH ratio are controlled in the study. The samples with combination of NaOH and water glass as alkaline activator were prepared by mixing these two solution and stirred for 2 minutes. Then this solution were mixed together with fly ash for 3 minutes and casted in the mould. The performance of the fly ash based geopolymer are evaluated by the compressive strength, water absorption and density at the early age of 1th, 3th and 7th days. Based on the study, at a concentration of 14M on 7th days had achieved the maximum compressive strength of 7.1 MPa for samples activated with NaOH only. Meanwhile, for geopolymer samples activated with a combination of the water glass and NaOH, the maximum strength of 33.33 MPa was recorded on 7th days of testing with NaOH concentration of 12 M. The water absorption for all geopolymer samples were ranging from 2.04 % to 2.78%, which are below the limit (3%). While the density of the geopolymer paste were in the range of 1552 kg/m3 to 1680 kg/m3, which are below the limit (2400 kg/m3). From the standpoint of strength of hardened geopolymer samples, the most effective alkaline activator in geopolymer is the combination of NaOH and water glass.

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“…The results of this review have been tabulated in Table 2.2. Effects of components and additives on geopolymer synthesis Brew et al 2007;Duxson et al 2005b,d,e,f;Fletcher et al 2005;Glukhovsky et al 1980;Keyte et al 2004;Kumar et al 2010;Lee and Van Deventer 2000a,b;2002a,b,c,e;Luz Granizo et al 2007;Phair et al 1999Phair et al , 2000bPhair et al , 2002aPhair et al , 2004Rees et al 2004;Rowles and Conner 2003;Van Jaarsveld and Van Deventer 1999a,b,c, e;Van Jaarsveld et al 2002Van Deventer 1999, 2003;Xu et al 2004;Deventer 2001, 2002a,b;Yip et al 2003a Geopolymer formation reactions, kinetics and mechanisms Buchwald et al 2009;Chen et al 2011a,b;Khale and Chaudhary 2007;Lee et al 1999;Lee and Van Deventer 2002e;Provis et al 2005a;Provis and Van Deventer 2004a,b;2007a,b,c;Provis and Van Deventer and Lukey 2005a;Sagoe-Crentsil and Weng 2007;Sindhunata et al 2004Sindhunata et al , 2006Weng and Sagoe-Crentsil 2007;Van Deventer 2000b, 2002;Zhang et al 2009;Zheng et al 2000 Geopolymer structural ordering, spectroscopic and microscopic analysis and modeling Duxson et al 2005a;,e, 2006c…”

Section: Waste Form Descriptionmentioning

confidence: 99%

Secondary Waste Form Down-Selection Data Package—DuraLith

Mattigod¹,

Westsik²

2011

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SummaryThe Hanford Site in southeast Washington State has 56 million gallons of radioactive and chemically hazardous wastes stored in 177 underground tanks (DOE 2010). The U.S. Department of Energy Office of River Protection, through its contractors, is constructing the Hanford Tank Waste Treatment and Immobilization Plant (WTP) to convert the radioactive and hazardous wastes into stable glass waste forms for disposal. Within the WTP, the pretreatment facility will receive the retrieved waste from the tank farms and separate it into two treated process streams. These waste streams will be vitrified, and the resulting waste canisters will be sent to offsite (high-level waste) and onsite (immobilized low-activity waste) repositories. As part of the pretreatment and immobilized low-activity waste processing, liquid secondary wastes will be generated that will be transferred to the Effluent Treatment Facility on the Hanford Site for further treatment. These liquid secondary wastes will be converted to stable solid waste forms that will be disposed of in the Integrated Disposal Facility.To support the selection of a waste form for the liquid secondary wastes from the WTP, Washington River Protection Solutions has initiated secondary waste form testing work at Pacific Northwest National Laboratory. In anticipation of a down-selection process for a waste form for the Solidification Treatment Unit to be added to the Effluent Treatment Facility, Pacific Northwest National Laboratory is developing data packages to support that down-selection. The objective of the data packages is to identify, evaluate, and summarize the existing information on the four waste forms being considered for stabilizing and solidifying the liquid secondary wastes. This data package developed for the DuraLith waste form includes information available in the open literature and from data obtained from testing currently underway.DuraLith is an alkali-activated geopolymer waste form developed by the Vitreous State Laboratory at The Catholic University of America (VSL-CUA) for encapsulating liquid radioactive waste. A DuraLith waste form developed for treating Hanford secondary waste liquids is prepared by alkali-activation of a mixture of ground blast furnace slag and metakaolin with sand used as a filler material.Based on optimization tests, solid waste loading of ~7.5% and ~14.7% has been achieved using the Hanford secondary waste S1 and S4 simulants, respectively. The Na loading in both cases is equivalent to ~6 M. Some of the critical parameters for the DuraLith process include hydrogen generation and heat evolution during activator solution preparation using the waste simulant, heat evolution during and after mixing the activator solution with the dry ingredients, and a working window of ~20 minutes to complete the pouring of the DuraLith mixture into molds. Results of the most recent testing indicated that the working window can be extended to ~30 minutes if 75 wt% of the binder components, namely, blast furnace slag and metakaolin are replace...

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Crystalline phase formation in metakaolinite geopolymers activated with NaOH and sodium silicate

Cited by 91 publications

References 18 publications

Degree of reaction and phase content of silica-based one-part geopolymers investigated using chemical and NMR spectroscopic methods

Degree of reaction and phase content of silica-based one-part geopolymers investigated using chemical and NMR spectroscopic methods

Comparative study on early strength of sodium hydroxide (NaOH) activated fly ash based geopolymer

Secondary Waste Form Down-Selection Data Package—DuraLith

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