Advanced Solid Geopolymer Formulations for Refractory Applications
Abstract
:1. Introduction
2. Experimental Details
2.1. Raw Material Properties
2.2. Design Mix Proportions
2.3. Experimental Methodology
3. Results and Discussion
3.1. Physical Appearance and Weight Loss
3.2. Compressive Strength
3.3. Thermal Fatigue Resistance of Geopolymers
3.4. Temperature Distribution Measurement
3.5. X-ray Diffraction Results
3.6. Scanning Electron Microscopy
4. Comparative Study of Refractory Potentials of Geopolymers
5. Conclusions
- All the geopolymer formulations used in this study retained their cubical shapes without cracks, spalling, or any physical disintegration post-exposure to 1100 °C for 1 h. The weight loss in the solid geopolymer formulations was more pronounced compared with their two-part liquid alkaline geopolymer counterparts.
- Advanced solid geopolymer formulations yielded better compressive strength after 1100 °C exposure compared with conventional liquid alkaline geopolymer formulations due to intensive mechano-chemical grinding in the process of making advanced solid geopolymers.
- The geopolymer mix made of 45-micron mullite, denoted as SR1, displayed its highest compressive strength, 84 MPa, after 1100 °C, and the crystalline phases of sanidine, annite, and cristobalite were identified in the sample. At 1100 °C, mullite recrystallized as a needle-like structure, densifying the matrix and increasing the compressive strength.
- The solid geopolymer mix made of alumina, denoted as SR3, had leucite as a crystalline phase at 1100 °C, which was responsible for its compressive strength of 64 MPa.
- Geopolymer mix SR1 retained its compressive strength after ten cycles of 1100 °C exposure. Mix SR1 displayed its highest compressive strength, 115.2 MPa, after four cycles, and SR3 had a gradual decrease in strength after each cycle, which further stabilized after eight cycles at 54.4 MPa.
- The temperature distribution profile of mix SR1 proves the superior thermal conductivity of the mix during direct flame exposure.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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Oxide Composition (%) | Physical Characteristics | ||||||
---|---|---|---|---|---|---|---|
CaO | SiO2 | Al2O3 | Fe2O3 | MgO | LOI | Specific Gravity | Strength Activity |
2.58 | 60.70 | 23.71 | 4.73 | 1.14 | 0.49 | 2.27 | 80.77% |
Aggregate | Al2O3 | SiO2 | Fe2O3 | CaO | TiO2 |
---|---|---|---|---|---|
Mullite | 57.41% | 40.62% | 0.56% | - | 1.22% |
Alumina | >93% | - | <0.3% | <5.5% | - |
Mix Notation | Fly Ash | Mullite | Alumina | KOH | K2SiO3 | RHS | Water |
---|---|---|---|---|---|---|---|
LR1 | 26 | 52 | - | 6 | 16 | - | - |
LR2 | 26 | 52 | - | 6 | 16 | - | - |
LR3 | 27 | - | 54 | 5 | 13 | - | - |
SR1 | 26 | 52 | - | 3 | 8 | - | 11 |
SR2 | 26 | 52 | - | 3 | 8 | - | 11 |
SR3 | 27 | - | 54 | 2.5 | 6.5 | 10 | |
SR4 | 25 | 51 | - | 7 | - | 4 | 13 |
Author | Geopolymer Mix Details | Mechanical Performance |
---|---|---|
Bezerra and Luz [60] | Geopolymers based on partially or fully replaced calcium aluminate cement (CAC) in high-alumina castables with sodium silicate as an activator. | A dosage of 2.7% weight CAC and 1.3% weight geopolymer at 1400 °C attained a flexural strength of 39.1 MPa. |
Farias et al. [61] | Metakaolin-based geopolymers with semi-insulating fused silica-containing castables. | The geopolymer-bonded castable exhibited a flexural strength of 6.24 MPa after exposure to 815 °C. |
Deutou et al. [62] | Metakaolin-, calcined bauxite-, and calcined talc-based geopolymer with kyanites of various particle sizes as fillers. Potassium hydroxide and potassium silicate as activators. | An 80 µm kyanite-filler-based geopolymer achieved a flexural strength of 45 MPa at a temperature of 1200 °C. |
Ahmed and Kishar [63] | Metakaolin geopolymer pastes incorporated with cement kiln dust and sodium hydroxide and sodium silicate as activators. | Geopolymer mix with 20% cement kiln dust withstood high temperatures with a strength of around 35 MPa at ambient temperature and around 22.5 MPa at 800 °C. |
Boum et al. [64] | Metakaolin–bauxite-blended geopolymer with sodium hydroxide and sodium silicate as activators. | The mechanical strength of the samples decreased from 35.2 to 11.1 MPa at room temperature. Compressive strength of 98 MPa at 1200 °C was achieved for a mix with 20% bauxite by weight. |
Yaşın and Ahlatcı [65] | Metakaolin-based geopolymer binder reinforced with fine alumina powder, sodium hydroxide, and sodium silicate. | The compressive strength of the sample after 1250 °C exposure was reported to be 134 MPa, whereas the unexposed sample had 30.41 MPa strength. |
Moosavi et al. [66] | Metakaolin-based geopolymer with microsilica (25% vol) and tabular alumina aggregates (75% vol). Potassium hydroxide as activator. | Flexural strength was reduced by 23.43 MPa after exposure to 1200 °C. Similar trends were observed in compressive strength with around 40% reduction in strength. |
Lahoti et al. [67] | Fly ash geopolymers with sodium and potassium-based activators individually and in combination. | A 30–40% increase in strength in the potassium-activator-based geopolymer, whereas the sodium-activator-based geopolymer reduced in strength (10%) after high-temperature exposure. After exposure to 500 °C, the compressive strength increased from 40 MPa to 59 MPa for the potassium-based geopolymer, and at 900 °C, it reduced to 54 MPa. |
King et al. [68] | Metakaolin geopolymer activated by combinations of sodium–potassium silicate and sodium–potassium hydroxide. | Lesser strength losses due to elevated temperature exposures were observed in geopolymers with high Si/Al ratios (>1.5) when they were exposed to 800 °C. The 3-day compressive strength reduction was 4–6%. |
Lahoti et al. [69] | Metakaolin-based geopolymers activated by sodium hydroxide and sodium silicate. | Compressive strength drastically decreased at 900 °C. At 25 °C, it was around 65 MPa, and at high temperatures, the strength dwindled to 6 MPa for a mix with a Si/Al ratio of 1.75. |
Kong et al. [14] | Metakaolin- and fly ash-based geopolymers with sodium silicate and potassium hydroxide activators. | Fly ash geopolymers increased in strength after 800 °C exposure, whereas metakaolin geopolymers decreased in strength. The metakaolin geopolymer’s unexposed strength was 38.5 MPa, and after exposure, it was 25.4 MPa. Fly ash’s unexposed strength was 59 MPa, and after exposure, it was 62.8 MPa. |
Guerrieri and Sanjayan [70] | Fly-ash–slag-based geopolymer in varying dosages with sodium activators. | Geopolymer mix with a 65%/35% (FA/Slag) ratio achieved the highest compressive strength. The residual compressive strength after 800 °C was 20 MPa. |
Rickard et al. [71] | Fly ash geopolymers with sodium silicate and sodium aluminate activators. | The compressive strength of samples increased after 1000 °C exposure, wherein the amount of Si or Al added by the activating solution was reduced. The effect was more pronounced in the sodium-aluminate-activated samples, which exhibited strength gains of almost five times, wherein 40% of the total Al was added via activating solution. |
Rickard et al. [72] | Fly ash geopolymers with sodium silicate and sodium aluminate activators. | After exposure to 1000 °C, the geopolymer sample exhibited an increase in compressive strength. The unexposed sample had a compressive strength of 33 MPa, whereas, after exposure, the strength increased to 132 MPa. |
Rickard et al. [73] | Fly ash geopolymers with sodium silicate and sodium hydroxide activators. | Geopolymers made from unreacted low-strength and low-density fly ash attained better strengths after high-temperature exposure (1000 °C) compared with geopolymer samples made from highly reactive and high-strength fly ash. In the former case, the strength increased from 28 MPa to 93 MPa. |
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Hussain, S.; Amritphale, S.; Matthews, J.; Paul, N.; Matthews, E.; Edwards, R. Advanced Solid Geopolymer Formulations for Refractory Applications. Materials 2024, 17, 1386. https://doi.org/10.3390/ma17061386
Hussain S, Amritphale S, Matthews J, Paul N, Matthews E, Edwards R. Advanced Solid Geopolymer Formulations for Refractory Applications. Materials. 2024; 17(6):1386. https://doi.org/10.3390/ma17061386
Chicago/Turabian StyleHussain, Shaik, Sudhir Amritphale, John Matthews, Niloy Paul, Elizabeth Matthews, and Richard Edwards. 2024. "Advanced Solid Geopolymer Formulations for Refractory Applications" Materials 17, no. 6: 1386. https://doi.org/10.3390/ma17061386
APA StyleHussain, S., Amritphale, S., Matthews, J., Paul, N., Matthews, E., & Edwards, R. (2024). Advanced Solid Geopolymer Formulations for Refractory Applications. Materials, 17(6), 1386. https://doi.org/10.3390/ma17061386