One-Part Geopolymer Mixes from Geothermal Silica and Sodium Aluminate

Hajimohammadi, Ailar; Provis, John L.; Deventer, J.S.J. van

doi:10.1021/ie8006825

Cited by 194 publications

(110 citation statements)

References 37 publications

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“…A new approach is the so-called ''one-part'' mixes [10] which are produced by a different synthesis route. One-part geopolymers contain the activator in solid form and therefore only water has to be added to initiate hardening, i.e.…”

Section: Introductionmentioning

confidence: 99%

“…By applying this approach, it is not necessary to store and handle highly alkaline waterglass or sodium hydroxide solutions, which avoids problems with carbonation and ageing of these solutions as well as problems with health and safety issues. This can provide a higher social and economic acceptance of these new binder materials [10,11]. Different ways to synthesize one-part geopolymers have been described [10,[12][13][14], and microstructural, mechanical and rheological studies are reported [10,[12][13][14][15][16][17][18][19][20].…”

Section: Introductionmentioning

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: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

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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“…Geopolymers for infrared spectroscopy study were synthesised using a 'onepart' (just add water) procedure [10]: solid washed geothermal silica (96% SiO 2 , from the Cerro Prieto geothermal power station, Mexico) and reagent-grade sodium aluminate (Aldrich) were blended to give the desired Si/Al ratios, and then mixed with water at a molar ratio of H 2 O/Na 2 O = 12. ATR-FTIR spectra of onepart mix geopolymers were collected using a Varian FTS 7000 FT-IR spectrometer, with a Specac MKII Golden Gate single reflectance diamond ATR attachment with KRS-5 lenses and heater top plate.…”

Section: Methodsmentioning

confidence: 99%

“…Bands at 1060 cm -1 are assigned to stretching of Si-O-Si bonds at the surface of the unreacted silica particles [15], and bands at 1100, 800 and 475 cm -1 relate to stretching, bending and rocking of the Si-O-Si bonds within the network of the [10] unreacted particles of geothermal silica [16]. Bands at 545, 625 and 700 cm -1 are related to vibrations in the unreacted solid aluminate [17].…”

Section: Time-resolved Infrared Spectroscopymentioning

confidence: 99%

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Analysing and Manipulating the Nanostructure of Geopolymers

Provis

Hajimohammadi

Rees

et al. 2009

Nanotechnology in Construction 3

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Abstract. Geopolymer concretes are currently being commercialised in Australia and elsewhere around the world, with a view towards enhancing the sustainability of the world's construction industry. The fundamental geopolymer binder is an aluminosilicate gel which displays key structural features on every length scale from Ångstroms up to centimetres, meaning that multiscale analysis is key to the development of a detailed understanding of geopolymer formation and performance. Here, we present results from investigations of geopolymer nanostructure, focusing on the use of infrared spectroscopy as an analytical tool. The effects of different combinations of precursors in geopolymer formation provides critical information, in particular with regard to the rate of reaction and its impact on the final distribution of elements and structures within the geopolymer binder. Formulations are designed so that the same composition is obtained by the use of precursors which release their constituent elements at very different rates under alkaline attack during geopolymerisation, and this provides essential information regarding the role of different elements in forming strong and durable geopolymer structures. Seeding the geopolymer mixture with very low doses of oxide nanoparticles presents several unexpected effects, both in terms of reaction kinetics and also in altering the nature of the zeolitic crystallites formed within the predominantly X-ray amorphous geopolymer binder.

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Microwave Enhanced Drying and Firing of Geopolymers

Gubb¹,

Baranova²,

Allan³

et al. 2011

Ceramic Engineering and Science Proceedings

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The feasibility of using microwave energy to dry and fire pre-cured geopolymers was experimentally demonstrated, and supported by analysis of published microwave dielectric data for geopolymers. Dielectric loss tangents and half power microwave absorption depths were calculated from published room temperature dielectric constant and loss values of various geopolymer compositions. The published data indicated that geopolymers would heat at room temperature with microwave energy. Several laboratory experiments were performed to test the heating behavior of sodium and potassium based geopolymer compositions. Experiments demonstrated more vigorous microwave heating with sodium geopolymers than with potassium geopolymers. Both compositions were dried in less than 10 minutes with pure microwave heating. Further heating with pure microwave energy resulted in non-uniform, rapid heating, or "thermal runaway", with localized melting of the geopolymer. Hybrid microwave heating with susceptors resulted in uniformly fired geopolymers, without melting. INTRODUCTIONInterest in geopolymers has accelerated in recent years due to their possible use in structural applications, dentistry, and hazardous waste stabilization, while maintaining a trivial environmental impact compared to traditional building materials. Many useful geopolymer compositions are fabricated by low temperature chemical reaction based curing processes 1 " 3 . Some recent research has been reported for using microwave energy to enhance curing and drying 4 ' 5 . Other research has focused on high temperature firing of geopolymers, which can develop stronger glass-ceramic materials 6 " 8 . In situations where heat is required, as in drying and firing, microwave energy provides an energy efficient alternative in place of conventional heating. Traditional radiant heating methods rely on thermal conduction to deliver heat throughout a material.Microwaves generate heat throughout the volume of the material, allowing faster, more uniform heating to occur. Volumetric microwave heating helps to overcome sluggish endothermic phase transitions, such as evaporation of water or decomposition of kaolin to metakaolin through the loss of hydroxides. Both drying and dehydration occur in the firing of geopolymers. In traditional heating, these reactions often require slow heating, as the endothermic reaction prevents heat from progressing into the product until the reaction completes first at the surface. Microwaves can generate heat throughout the part despite an endotherm 9 .When microwave energy is the sole source of heat, a material that absorbs microwave energy will heat volumetrically, but cool from the surface. This situation creates an "inverse temperature profile" in which the sample is warmer inside and cooler at the surface during heating. This is opposite of traditional radiant heating where the material will be cooler in the center. In some materials, the inverse temperature profile can lead to thermal runaway -where the hotter center heats better than the cooler sur...

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One-Part Geopolymer Mixes from Geothermal Silica and Sodium Aluminate

Cited by 194 publications

References 37 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

Analysing and Manipulating the Nanostructure of Geopolymers

Microwave Enhanced Drying and Firing of Geopolymers

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