Showing papers on "Geopolymer published in 2002"

Environmentally Driven Geopolymer Cement Applications.

Abstract: Summary: Environmentally driven geopolymer applications are based on the implementation of (K,Ca)Poly(sialate-siloxo) / (K,Ca)-Poly(sialate-disiloxo) cements. In industrialized countries (Western countries) emphasis is put on toxic waste (heavy metals) and radioactive waste safe containment. On the opposite, in emerging countries, the applications relate to sustainable development, essentially geopolymeric cements with very low CO2 emission. Both fields of application are strongly dependent on politically driven decisions. a) Heavy metals waste encapsulation: This application started in 1987, in Canada, with the financial support of CANMET Ottawa, Ontario Research Foundation, Toronto, and Comrie Consulting. It was dedicated to the stabilization of based metal mine tailings. Laboratory results were excellent, yet the experimentation stopped because of lack of political support. b) Uranium mine tailings and radioactive sludge: Started in 1994 within the research project GEOCISTEM, funded by the European Union. The GEOCISTEM project was aimed at manufacturing cost-effectively new geopolymeric cements. It was experimented on two important uranium-mining locations of WISMUT, former East Germany, with the collaboration of BPS Engineering. Germany. First on sludges containing radionuclides, toxic heavy metals and hydro-carbons. Then, a pilot experimentation totalizing 30 tons of low-level radioactive waste was run in 1998 at the WISMUT's Schlema-Alberod water treatment plant. The geopolymer technology gives a monolithic product, which can be easily handled, stored and monitored. It requires only simple mixing and molding technology known from conventional solidification methods. Our results clearly show that solidification with Geopolymeric Cement (K,Ca)-Poly(sialate-siloxo) is a prime candidate to fill cost-efficiently the gap between conventional concrete technology and vitrification methods. Due to the reduced effort to prepare, operate and close the landfill, geopolymeric solidification leads to approximately the same unit cost as by conventional Portland cement, but provides in most aspects the performance of vitrification. c) Green-House CO2 mitigation, low CO2 geopolymer cements: Started in 1990 at PennState University, Materials Research Laboratory, USA, and continued within the frame of the European Project GEOCISTEM. In 2002, it has been declared technological priority by the China’s government. The production of 1 tone of Geopolymeric cement generates 0.180 tones of CO2, from combustion carbon-fuel, compared with 1.00 tones of CO2 for Portland cement. Geopolymeric cement generates six (6) times less CO2 during manufacture than Portland cement. This simply means that, in newly industrializing countries, six (6) times more cement for infrastructure and building applications might be manufactured, for the same emission of green house gas CO2.

Characterization of Fly-Ash-Based Geopolymeric Binders Activated with Sodium Aluminate

Abstract: Properties and characteristics of sodium silicate activated fly-ash-based geopolymers have been extensively investigated, but the utilization of sodium aluminate activation has received little attention. The present work, therefore, examines the properties of the starting materials and sodium aluminate solutions and their effect on the final material properties and microstructure of fly-ash-based geopolymers. To achieve this, starting sodium aluminate solutions were characterized with ATR-FTIR and 27Al NMR spectroscopies to determine the coordination state of aluminum as a function of solution concentration and [OH]/[Al] ratio. Various fly-ash-based geopolymeric matrixes were synthesized utilizing fly ash, kaolinite, K-feldspar, and slag as the mineral aluminum sources. The matrixes were activated with alkali silicate or alkali aluminate solutions as a function of pH, concentration, and alkali ion (Na+ or K+). FTIR and XRD studies combined with compressive strength tests demonstrated that in certain cases...

Effects of Anions on the Formation of Aluminosilicate Gel in Geopolymers

Abstract: This work demonstrates that an increase in soluble silicate concentration over ∼200 mM in an aqueous alkaline solution (pH = ∼13.95) can significantly increase the reactivity of a Class F fly ash at room temperature. The greatly increased dissolution of the fly ash primary phase(s) and the subsequent secondary precipitation are responsible for the formation of an aluminosilicate gel similar to the major binding phase of a geopolymer. On the basis of this observation, a reaction model was developed to simulate aluminosilicate gel formation in a real geopolymeric system. In this work, potassium salts of chloride, carbonate, oxalate, and phosphate (KCl, K2CO3, K2C2O4·H2O, and K2HPO4) were used as solution contaminants. It was found that the anions (Cl-, CO32-, C2O42-, and PO43-) significantly affected the formation kinetics as well as the nature of the aluminosilicate gel formed in the reaction model. This observation could be successfully used to mechanistically explain the retardation effects of the variou...

Binding geopolymeric mixture

Abstract: A Binding geopolymer mix, hardening at temperatures from 15 to 95 degrees C, designed for the production of paste, malt and concrete consisting of 35.01 to 93.9% by weight of fly ash with a specific surface of 100 to 600 m /kg, 0 to 40% by weight of material with a specific surface of 200 to 600 m /kg, selected from a group composed of ground Portland clinker, granulated blast-furnace slag and 5 to 15% of an alkali activator, for example a mix of sodium and/or potassium silica glass and NaOH or KOH, expressed as % by weight of Na2O or K2O, with a ratio of SiO2/Na2O or K2O equalling 0.1 to 1.0, and 1.1 to 9.99% by weight of aluminous admixtures containing at least 35% by weight of Al2O3, for example calcium aluminate, sintered aluminous cement, gibbsite, boemite, anhydrous Al2O2, calcinated or non-calcinated bauxite, aluminous clay, calcareous clay, aluminium hydroxide or mica. Advantageously the aluminous admixture should have more than 50% of particles smaller than 60 microns.

Geopolymer stone for building and decoration and method for obtaining same

Abstract: The invention concerns a geopolymer stone for building and decoration, similar in appearance to natural stone. It consists of: 65 to 95 wt. % of residual rock derived from a naturally weathered rock and/or dendrital rock derived from erosion; 5 to 25 wt. % of geopolymer binder of poly(sialate), poly(sialate-siloxo) and/or poly(sialate-disiloxo) type. Said geopolymer stone is for example sandstone similar to natural rocks belonging to the category of silicious cement or pellitic cement sandstones, or foraminiferous limestone similar to natural rock belonging to the category of limestones with organisms, or arkose-type granite similar to natural stone belonging to the category of arkoses. The geopolymer stone is used as outdoor and/or indoor covering with Portland cement concrete core, dense or expanded (cellular concrete).

Heat-insulating composite material molded part production comprises mixing a high porous granulate based on grain and/or leguminous plant with a geopolymer, molding the mixture into molded body, and hardening

Abstract: Production of a heat-insulating composite material molded part comprises mixing 50-90 vol.% of a high porous granulate based on grain and/or leguminous plant with 50-10 vol.% of a geopolymer made from a mixture of aluminosilicate solids and a hardener in the form of an aqueous solution of alkali hydroxide and alkali waterglass and/or alkali carbonate, molding the mixture into molded body, and hardening for 1-10 hours at 20-60 degrees C. Preferred Features: The granulate is sprayed with the geopolymer. The geopolymer is made porous by adding metallic aluminum or other suitable additive.

Geopolymer cement useful for building comprises mellilite, aluminosilicate and quartz particles in an amorphous vitreous matrix comprising a poly(sialate-disiloxo) geopolymer

Abstract: Geopolymer cement comprises mellilite, aluminosilicate and quartz particles with a mean diameter below 50 mum in an amorphous vitreous matrix comprising a poly(sialate-disiloxo) geopolymer (I). Geopolymer cement comprises mellilite, aluminosilicate and quartz particles with a mean diameter below 50 mum in an amorphous vitreous matrix comprising a poly(sialate-disiloxo) geopolymer of formula (I): (Na,K,Ca)(Si-O-Al-O-Si-O-Si-O) (I)