Chemical optimisation of the compressive strength of aluminosilicate geopolymers synthesised by sodium silicate activation of metakaolinite

Rowles, Matthew R.; O’Connor, B. H.

doi:10.1039/b212629j

Cited by 405 publications

(226 citation statements)

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“…In contrast, FA based geopolymer mortars cured under ambient temperatures usually exhibit slower early strength development and setting time, which is likely to be due to a low content of iron oxide, calcium hydroxide (Ca(OH) 2 ), and reactive silica [18]. These mortars however showed identical compressive strength (62-66 MPa) after 24 hour curing at 60-75 °C [19]. High temperature curing for at least 6 hours is typically recommended for FA based geopolymer concrete in order to accelerate the pozzolanic reaction and develop the mechanical properties [20,21].…”

Section: Introductionmentioning

confidence: 96%

Development of geopolymer mortar under ambient temperature for in situ applications

Al-Majidi

Λαμπρόπουλος

Cundy

et al. 2016

Construction and Building Materials

288

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Geopolymer concrete technology involves production of more environmentally friendly waste material-based concrete which could be a viable solution for conventional concrete replacement. Typical fly ash-based geopolymer concrete however requires high temperature curing treatment in order to develop sufficient early strength properties, which is considered a severe limitation for cast-in-place concrete applications. Most previous studies on geopolymer concrete have focused on the properties of concretes pre-hardened by heat curing and/ or by aggressive chemical treatment (e.g. alkali activation using concentrated sodium hydroxide (NaOH)). The current study presents an extensive experimental investigation on the mechanical and microstructural properties of geopolymer concrete mixes prepared with a combination of fly ash and slag cured under ambient temperature. 'User friendly' geopolymer mixes were produced using fly ash (FA) and Ground Granulated Blast furnace Slag (GGBS) mixed together with potassium silicate with molar ratio equal to 1.2 (as the activator) and water. The results indicated that heat curing treatment can be avoided by partial replacement of fly ash with slag. The compressive strength of the examined mixes was found to be in the range of 40-50MPa for 40 % and 50 % GGBS replacement mixtures respectively. Moreover, the flexural and direct tensile strengths of geopolymer mixes are considerably improved as the GGBS content is increased.Based on FTIR and SEM/EDS analysis, the inclusion of a higher content of GGBS resulted in a denser structure by formation of more hydration products.Keywords: Fly ash, slag, ambient temperature, user friendly geopolymer mortar *Manuscript Click here to view linked References 2 IntroductionThere are many environmental issues associated with the production of Ordinary Portland cement (OPC), such as consumption of 5% of natural resources, and generation of 5-7 % of total global anthropogenic carbon dioxide emissions [1][2][3][4]. This has led to an urgent need for the development of alternative materials that may provide technically viable alternative solutions to conventional cementitious concrete, with more favourable environmental credentials. Geopolymer concrete manufacture is one of the most promising techniques which has been developed in the last few years. Utilization of geopolymer materials can reduce 80% of greenhouse gas emissions associated with material production, and overcome issues related to cement production and unregulated disposal of industrial materials by recycling these materials in geopolymer manufacture [5][6][7].Geopolymers are inorganic by-product materials, rich in silicon (Si) and aluminium Five different mixtures of geopolymer mortar proportions were examined with various ratios of GGBS to total binder (10%, 20%, 30%, 40% and 50 %, Table 2). Based on preliminary experimental studies undertaken during the current project, the optimum mix design (in terms of mechanical strength and workability) was achieved using water, alkaline activator...

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Section: Introductionmentioning

confidence: 96%

Development of geopolymer mortar under ambient temperature for in situ applications

Al-Majidi

Λαμπρόπουλος

Cundy

et al. 2016

Construction and Building Materials

288

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“…Se ha identificado (11) que en este tipo de mezclas cementantes la estructura es dominada por un gel del tipo aluminosilicato cuando los contenidos de escoria son menores al 40%, la cual presenta poros de gran tamaño con agua libre que favorece la pérdida en peso a bajas temperaturas (31). Esta pérdida de peso es asociada a la remoción de los grupos hidroxilo que pueden estar condensados en la superficie del gel cementante (12,32), y del agua químicamente enlazada que está presente en los productos de reacción de tipo zeolítico, que se forman en los sistemas de metacaolín activado alcalinamente (33).…”

Section: Characterisation Of Mortars Exposed To High Temperaturesunclassified

“…It has been identified (11) that in these types of blended binders the structure is dominated by an aluminosilicate type gel at slag contents lower than 40%, which presents larger pores containing free water, thus favouring weight loss at lower temperatures (31). The consequent weight loss is associated with the removal of the hydroxyl groups from the surface of the binding gel (12,32), and the zeolitic-like water that is present in the reaction products formed in geopolymers based on alkali-activated metakaolin (33).…”

Section: De Sustitución De Al Y Posible Inclusión De Sodio (C-(n)-a-smentioning

confidence: 99%

Desempeño a temperaturas altas de morteros y hormigones basados en mezclas de escoria/metacaolín activadas alcalinamente

Bernal

Gutiérrez²,

Ruiz³

et al. 2012

Mater. construcc.

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RESUMENEste artículo evalúa el desempeño de morteros y hormigones basados en mezclas de escoria siderúrgica (GBFS)/metacaolín (MK), activadas alcalinamente expuestos a temperaturas altas. Se identifica una elevada estabilidad en morteros con contenidos de MK de hasta un 60% cuando se exponen a temperaturas de 600 ºC, con una resistencia residual de 20 MPa posterior a la exposición a esta temperatura. Por otra parte, la exposición a temperaturas más elevadas conduce al agrietamiento de los hormigones como consecuencia de una elevada contracción de la matriz cementante y las restricciones por efecto de los áridos, especialmente en aquellos especímenes con cementantes que contienen altos contenidos de MK. Se identifican diferencias significativas en las propiedades de absorción de agua de morteros y hormigones, y esto se relaciona con las divergencias en el desempeño de estos materiales posterior a la exposición a temperaturas altas. Esto indica que el desempeño a temperaturas elevadas de morteros de activación alcalina no es completamente transferible a hormigones, ya que los sistemas difieren en permeabilidad. Las diferencias en los coeficientes de expansión térmica entre matriz cementante y los áridos gruesos contribuyen al macrofisuramiento del material y su consecuente reducción de propiedades mecánicas.Palabras claves: cementos alcalinos, altas temperaturas, escoria siderúrgica, metacaolín, propiedades mecánicas. SUMMARYThis paper assesses the performance of mortars and concretes based on alkali activated granulated blastfurnace slag (GBFS)/metakaolin (MK) blends when exposed to high temperatures. High stability of mortars with contents of MK up to 60 wt.% when exposed to 600°C is identified, with residual strengths of 20 MPa following exposure to this temperature. On the other hand, exposure to higher temperatures leads to cracking of the concretes, as a consequence of the high shrinkage of the binder matrix and the restraining effects of the aggregate, especially in those specimens with binders containing high MK content. A significant difference is identified between the water absorption properties of mortars and concretes, and this is able to be correlated with divergences in their performance after exposure to high temperatures. This indicates that the performance at high temperatures of alkali-activated mortars is not completely transferable to concrete, because the systems differ in permeability. The differences in the thermal expansion coefficients between the binder matrix and the coarse aggregates contribute to the macrocracking of the material, and the consequent reduction of mechanical properties. . La principal diferencia entre estas dos clases de cementantes es la presencia de calcio en la escoria lo que promueve la formación de una estructura compuesta fundamentalmente por geles de silicatos cál-cicos hidratados (C-(A)-S-H) (2), mientras que en los geopolímeros se forman geles del tipo aluminosilicato sódi-co hidratado (N-A-S-H) (4). KeywordsEl uso tanto de metacaolín como de escoria activada a...

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“…It significantly effects to developing of mechanical properties of concrete [9]. Other study proved that the influence of curing temperature changed the formation of the crystal [10,11] , but at longer duration of curing time causes less impact in the formation of crystals.…”

Section: Compressive Strengthmentioning

confidence: 99%

The Effect of Temperature Curing on Geopolymer Concrete

Ekaputri¹,

Priyanka²

2017

MATEC Web Conf.

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.This study presents curing temperature influences to behaviors of geopolymer concrete. The concrete was fly ash based, with the ratio of fly ash to alkaline activator was 65%:35%. Ratio coarse aggregate to fine aggregate was 60%:40%, ratios Na 2 SiO 3 /NaOH were 1.5:2 and 2.5. A polycarboxilate superplasticizer with ratio was 2% to fly ash weight. Form of the test specimens were cylinder with diameter of 10 cm and 20 cm high. Steam curing conducted were at 40ᴼC, 60ᴼC and 80ᴼC for 24 hours. The control specimens were treated at normal moist curing. Tests conducted were compressive strength, tensile strength, porosity and elasticity modulus. The results indicated that at the elevated temperature the compressive strength increases as well as tensile strength but decreases the closed porosity of specimens. The elasticity modulus had a similar tendency.

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Chemical optimisation of the compressive strength of aluminosilicate geopolymers synthesised by sodium silicate activation of metakaolinite

Cited by 405 publications

References 22 publications

Development of geopolymer mortar under ambient temperature for in situ applications

Development of geopolymer mortar under ambient temperature for in situ applications

Desempeño a temperaturas altas de morteros y hormigones basados en mezclas de escoria/metacaolín activadas alcalinamente

The Effect of Temperature Curing on Geopolymer Concrete

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