Study on the Activity of Metakaolin Produced by Traditional Rotary Kiln in China
Abstract
:1. Introduction
2. Materials and Methods
2.1. Materials
2.2. Geopolymer Gel Preparation (20 °C, 50% Relative Humidity)
2.3. Samples Preparation
2.4. Chemical Detection
2.5. Immersion Test
3. Results
3.1. Coal-Based Metakaolin Activity
3.2. Ordinary Metakaolin Activity
4. Conclusions
- (1)
- The kaolinite accounted for a large proportion of coal-based kaolin, and the product of coal-based kaolin calcined in a rotary kiln was mainly amorphous aluminum silicate. Due to the over calcination of kaolin, aluminum in amorphous aluminum silicate mainly existed in the form of Al (VI). Some quartz and corundum were also formed in this calcination process, and they did not participate in the reaction of metakaolin and alkali activators to form geopolymer. When the mixture of coal-based metakaolin and alkali activator hardens after reacting, these crystals and geopolymer are connected by intermolecular forces, and upon encountering water, the crystals and geopolymer separated as intermolecular forces broke.
- (2)
- Low kaolinite purity and over calcination were two negative effects on the activity of ordinary metakaolin. The pyrophyllite and illite in ordinary metakaolin were difficult to produce amorphous substances that could be used as geopolymer raw materials in a traditional rotary kiln. Their calcination led to excessive sillimanite and cristobalite, which were difficult to react in an alkali solution at room temperature; over calcination further reduced the content of amorphous substances in the reaction products. The geopolymer content in the hardened mixture after the reaction of ordinary metakaolin and alkali activator was very small. When encountering water, the whole mixture was quickly destroyed with the break of intermolecular force.
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Coal-Based Kaolin | Ordinary Kaolin | ||||||
---|---|---|---|---|---|---|---|
Element | Conc | Compound | Conc | Element | Conc | Compound | Conc |
Si | 49.268% | SiO2 | 49.088% | Si | 57.432% | SiO2 | 52.815% |
Al | 37.751% | Al2O3 | 44.144% | Al | 38.724% | Al2O3 | 45.355% |
Fe | 6.500% | Fe2O3 | 3.136% | Ti | 1.308% | TiO2 | 0.704% |
Ti | 3.581% | TiO2 | 2.181% | Fe | 1.060% | Fe2O3 | 0.473% |
Ca | 0.990% | CaO | 0.523% | K | 0.665% | K2O | 0.265% |
K | 0.931% | K2O | 0.424% | Ca | 0.444% | CaO | 0.201% |
Cl | 0.243% | Cl | 0.094% | Zr | 0.106% | ZrO2 | 0.044% |
Zr | 0.212% | SO3 | 0.089% | Cl | 0.039% | SO3 | 0.034% |
V | 0.114% | ZrO2 | 0.084% | S | 0.035% | V2O5 | 0.026% |
S | 0.093% | V2O5 | 0.077% | V | 0.030% | Cl | 0.014% |
Sr | 0.077% | P2O5 | 0.053% | Cr | 0.029% | CuO | 0.014% |
Cr | 0.069% | Cr2O3 | 0.031% | Zn | 0.023% | ZnO | 0.009% |
P | 0.067% | SrO | 0.028% | Sr | 0.021% | Cr2O3 | 0.008% |
Ga | 0.024% | Ga2O3 | 0.010% | Pb | 0.019% | Ga2O3 | 0.008% |
Nb | 0.019% | MnO | 0.008% | Ga | 0.018% | MnO | 0.007% |
Th | 0.018% | NbO | 0.007% | Mn | 0.017% | SrO | 0.007% |
Mn | 0.017% | Y2O3 | 0.006% | Cu | 0.013% | PbO | 0.007% |
Y | 0.014% | ThO2 | 0.006% | Nb | 0.010% | NbO | 0.006% |
Ni | 0.008% | NiO | 0.006% | Y | 0.007% | Y2O3 | 0.003% |
Cu | 0.004% | CuO | 0.005% |
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Cao, R.; Fang, Z.; Jin, M.; Shang, Y. Study on the Activity of Metakaolin Produced by Traditional Rotary Kiln in China. Minerals 2022, 12, 365. https://doi.org/10.3390/min12030365
Cao R, Fang Z, Jin M, Shang Y. Study on the Activity of Metakaolin Produced by Traditional Rotary Kiln in China. Minerals. 2022; 12(3):365. https://doi.org/10.3390/min12030365
Chicago/Turabian StyleCao, Rongchuan, Zheng Fang, Man Jin, and Yu Shang. 2022. "Study on the Activity of Metakaolin Produced by Traditional Rotary Kiln in China" Minerals 12, no. 3: 365. https://doi.org/10.3390/min12030365