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| Sl. no. | Authors/ref. | Year |
Test conducted | Types of binder and alkali activator used | Curing regime | Observations |
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(1) | Goretta et al. [6] | 2004 | Compressive strength. | Class C fly ash and granulated blast-furnace slag,
sodium silicate. | Hot air oven curing at 80°C to 120°C and ambient temperature. | The response was attributed to material loss by propagation of both lateral and radial cracks and presence of microcracks and aggregates in the matrix. |
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(2) | Bakharev [7] | 2005 | Compressive strength. FTIR, XRD, and SEM. | Class F fly ash.
Sodium silicate and sodium hydroxide.
Potassium hydroxide | Hot air oven at 75°C to 150°C. | An increase of temperature of heat treatment caused a decrease of Si/Al ratios in aluminosilicate gel, and long curing at room temperature narrowed the range of distribution of the Si/Al ratios. |
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(3) | Bakharev [7] | 2005 | Compressive strength. | Class F fly ash.
Sodium silicate and sodium hydroxide. | Hot air oven curing at 75°C and 95°C. | Fly ash activated by sodium silicate, 6 h heat curing is more beneficial than 24 h heat.
Fly ash activated by sodium hydroxide had more stable strength properties. |
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(4) | Fernández-Jiménez et al. [8] | 2005 | Compressive strength. | Class F fly ash and sodium hydroxide solution. | Hot air oven curing at 80°C. | The particle size distribution and the mineral composition of the starting fly ash, the type and concentration of the activator, and so forth. |
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(5) | Duxson et al. [9] | 2005 | Compressive strength. | Metakaolin.
Sodium silicate and sodium hydroxide solution. | Hot air oven curing at 80°C. | This demonstrates that the characteristics of geopolymers can be tailored for applications with requirements for specific microstructural, chemical, mechanical, and thermal properties. |
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(6) | Bakharev [10] | 2006 | Compressive strength, shrinkage measurements, XRD, and SEM. | Fly ash.
Sodium silicate and sodium hydroxide.
Potassium hydroxide | Hot air oven at 100°C. | Geopolymer materials prepared using class F fly ash and sodium and potassium silicate show high shrinkage as well as large changes in compressive strength with increasing fired temperature in the range 800–1200°C. |
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(7) | Škvára et al. [11] | 2006 | Compressive strength. | Fly ash and ground blast-furnace granulated slag.
Sodium hydroxide. | Hot air oven curing at 100°C–120°C. | The hardness of geopolymer is approximately twice higher than for OPC that could indicate less deformability and higher brittleness. |
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(8) | Chindaprasirt et al. [12] | 2007 | Compressive strength. | Lignite fly ash (FA)
Sodium silicate and sodium hydroxide solution as alkali activators. | Hot air oven curing at 120°C. | The samples with a high strength were obtained using the delay time after molding and before subjecting the sample to heat of 1 h with heat curing in the oven at 75°C of not less than two days. |
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(9) | Kong et al. [13] | 2007 | Compressive strength. | Metakaolin and low-calcium fly ash.
Grade D sodium silicate solution and potassium hydroxide. | Hot air oven curing at 100°C. | Fly ash pores contain higher proportion of microspores than metakaolin geopolymer. Fly ash-based geopolymer gives better strength than metakaolin. |
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(10) | Temuujin et al. [14] | 2009 | Compressive strength. | Fly ash.
Sodium silicate and sodium hydroxide solution. | Hot air oven curing at 75°C and 100°C. | Addition of the calcium compounds CaO and Ca(OH)2 improves mechanical properties and cured at ambient temperature.
Calcium compound addition reduces mechanical properties cured at elevated temperatures. |
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(11) | Kong and Sanjayan [15] | 2008 | Compressive strength. | Low-calcium (class F) fly ash. Sodium silicate solution and potassium hydroxide. | Hot air oven curing at 80°C. | The strength declined with inclusion of geopolymer/aggregate composites.
While aggregates undergo expansion at elevated temperatures, the geopolymer matrix experienced contraction. |
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(12) | Diaz et al. [16] | 2010 | Compressive strength. | Class F fly ash.
Sodium silicate and sodium hydroxide solution. | Hot air oven curing at 80°C. | Higher amount of fine particles will result in higher surface area, higher reactivity resulting in higher compressive strength. |
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(13) | Kong and Sanjayan [17] | 2010 | Compressive strength. | Class F fly ash.
Sodium silicate and sodium hydroxide. | Hot air oven curing at 100°C. | The rate of expansion of the aggregate with temperature is an influential factor in the performance of geopolymer concrete under elevated temperatures. |
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(14) | Kumar et al. [18] | 2010 | Compressive strength.
FTIR, XRD, and SEM. | Fly Ash.
Sodium hydroxide. | Hot air oven at 100°C to 250°C. | Combined effect of particle size and change in reactivity due to mechanical activation altered the geopolymerisation reaction.
The improvement in physical properties is related to the intrinsic structure developed due to enhanced geopolymerisation. |
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(15) | Wongpa et al. [19] | 2010 | Compressive strength. | Fly ash and rice husk bark ash.
Sodium silicate and sodium hydroxide solution. | Hot air oven curing at 75°C to 125°C. | Paste content and the aggregate content P/Aggregate of 0.34 and Si/Al of 0.63 showed the highest compressive strength. |
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(16) | Jämstorp et al. [20] | 2010 | Compressive strength. | Kaolin (Al2Si2O5(OH)4), fumed silica.
Metakaolin and sodium hydroxide (NaOH).
Fentanyl base and Zolpidem tartrate.
| Hot air oven curing at 100°C to 150°C. | Samples with pore sizes of about 40 nm, exhibited a satisfying initial release of 60–80% of the API content within 10 h and nearly all within 24 h, as well as fairly high compression strengths of 50–60 MPa. |
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(17) | Elimbi et al. [21] | 2011 | Setting time, linear shrinkage, compressive strength, XRD, and SEM. | Metakaolin, kaolinite, and sodium hydroxide and sodium silicate. | Calcined at 450°C and ambient temperature.
| Above 700°C, there is an increase of setting time.
The compressive strength increases when the calcination temperature of kaolinite clays is between 500 and 700°C but drops above 700°C. |
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(18) | Natali et al. [22] | 2011 | Flexural strength and fracture toughness. | Metakaolin, ladle slag, and sodium hydroxide and sodium silicate. | Calcined at 700°C for 5 hours. | Geopolymer matrix is able to determine a flexural strength increment, ranging from 30% up to 70% depending on the fiber type, compared to the unreinforced material. |
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(19) | Nazari et al. [23] | 2011 | Compressive strength. | Seeded fly ash and rice husk bark ash.
Sodium silicate and sodium hydroxide. | Hot air oven at 80°C. | The highest strength was achieved using a 12 M NaOH solution. Oven curing of the specimens at 80°C was found to be the optimum temperature. |
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(20) | McLellan et al. [24] | 2011 | Compressive strength. | Comparative study of OPC and fly ash. Sodium silicate and sodium hydroxide solution. | Hot air oven at 100°C. | There is an estimated 44–64% improvement in greenhouse gas emissions over OPC. Emissions from geopolymer concrete can be 97% lower up to 14% higher. |
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(21) | Somna et al. [25] | 2011 | Compressive strength. | Fly ash. Sodium silicate and sodium hydroxide solution. | Hot air oven at 100°C. | Sodium hydroxide-activated ground fly ash cured at room temperature can be produced with reasonable strength.
Ground fine fly ash can be used as a source material for making geopolymer cured at ambient temperature. |
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