Performance of Selected South African Kaolinitic Clays for Limestone Calcined Clay Cement
Abstract
:1. Introduction
2. Materials and Methods
2.1. Material Characterisation
2.1.1. Particle Size Distribution (PSD)
2.1.2. Chemical Composition
2.1.3. Kaolinite Content in Clay
2.1.4. SCMs Morphology and Mortar Microstructure
2.1.5. Mortar Hydration and Binder Phases
2.2. Mortar Mixture and Strength
2.3. Porosity
3. Test Results and Discussion
3.1. Binder Properties
3.1.1. Particle Size Distribution
3.1.2. Kaolinite Content
3.1.3. Chemical Composition
3.1.4. Binder Mineralogy
3.1.5. Calcined Clay and Limestone Morphology
3.1.6. Mortar Hydrate Mineralogy and Content
3.2. Mortar Properties
3.2.1. Fresh State
3.2.2. Microstructure and Porosity
- 2D microstructural analysis
- 3D void microstructure
3.3. Compressive Strength
4. Conclusions
- Varied kaolinite content of raw clay can yield similar pozzolanic oxide (SiO2 + Al2O3) content of the calcined clay, the main component of the target metakaolin (Al2O7Si2) from the raw clay calcination. The calcined clay particles tend to be flat, irregular, and elongated, with fibril surface cracks. Pozzolanic activity of the LC3 is directly proportional to the kaolinite content and can be associated with the consumed portlandite.
- Increased kaolinite content of LC3 tends to increase the consistency of the mortar mixture, thereby reducing the demand for water reducer. Limestone and metakaolin densify the microstructural pores of LC3 systems by forming carbo-aluminates coupled with filler effects and pozzolanic reaction. It is noted that at 28 days, not all the calcined clay particles are fully hydrated. The limestone can also contribute to pure filler effects.
- The results suggest that SEM 2D microstructure evaluation may not be adequate to indicate the overall porous nature of LC3 mortars. The degree of limestone hydration tends to be more important than kaolinite content for microscale void refinement of LC3 mortar.
- The observed hydration and microstructure mineralogy of the South African clay samples (LC3) seem to correlate well with the existing literature on LC3 from other regions. Therefore, achieving the designed strength for the control OPC with the LC3 with a minimum kaolinite content of 40% is possible, and consideration must be given to the intrinsic content of limestone in commercially available Portland cement.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Acknowledgments
Conflicts of Interest
Appendix A
OPC Statistical Summary of Pore Diameter | Mfn Statistical Summary of Pore Diameter | ||
Mean | 0.30426 | Mean | 0.294894 |
Standard Error | 0.00042 | Standard Error | 0.000412 |
Median | 0.2657 | Median | 0.2621 |
Mode | 0.2121 | Mode | 0.2121 |
Standard Deviation | 0.152626 | Standard Deviation | 0.133591 |
Sample Variance | 0.023293 | Sample Variance | 0.017847 |
Kurtosis | 86.38983 | Kurtosis | 52.39284 |
Skewness | 5.805636 | Skewness | 4.925806 |
Range | 7.0354 | Range | 4.3761 |
Minimum | 0.1225 | Minimum | 0.1225 |
Maximum | 7.1579 | Maximum | 4.4986 |
Sum | 40207.3 | Sum | 30,980.39 |
Count | 132,148 | Count | 105,056 |
OPC Statistical Summary Of Pore Diameter | MFN Statistical Summary of Pore Diameter | ||
Mean | r | Mean | 0.287649713 |
Standard Error | 0.00032 | Standard Error | 0.00030636 |
Median | 0.2449 | Median | 0.2488 |
Mode | 0.2121 | Mode | 0.2121 |
Standard Deviation | 0.130085 | Standard Deviation | 0.142124828 |
Sample Variance | 0.016922 | Sample Variance | 0.020199467 |
Kurtosis | 39.17251 | Kurtosis | 79.71507142 |
Skewness | 4.337844 | Skewness | 5.50304214 |
Range | 3.5701 | Range | 6.4996 |
Minimum | 0.1225 | Minimum | 0.1225 |
Maximum | 3.6926 | Maximum | 6.6221 |
Sum | 46,136.06 | Sum | 61,906.8206 |
Count | 165,527 | Count | 21,5216 |
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Country | Deposit Location | Estimated Amount |
---|---|---|
South Africa | Hopefield—Western Cape | 50 million tonnes |
Grahamstown—Eastern Cape | 60 million tonnes | |
Bronkhorstspruit—Gauteng | >35 million tonnes |
Notation | Cement (g) | Clay (g) | Limestone (g) | Gypsum (g) | Water (g) | Sand (g) | Superplasticiser (g) |
---|---|---|---|---|---|---|---|
OPC | 500 | 0 | 0 | 0 | 250 | 1125 | 5 |
EXW | 250 | 150 | 75 | 25 | 5.5 | ||
BFN | 9 | ||||||
MFN | 9 |
Clay Sample | MFN | EXW | BFN |
---|---|---|---|
Kaolinitic content | 29.5 | 41.6 | 32.8 |
Sample Name | Al2O3 (%) | CaO (%) | Cr2O3 (%) | Fe2O3 (%) | K2O (%) | MgO (%) | MnO (%) | Na2O (%) | P2O5 (%) | SiO2 (%) | TiO2 (%) | LOI (%) | Sum of Conc. (%) | PO (%) |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
MFN | 21.86 | 0.12 | 0.01 | 0.74 | 2.72 | 0.23 | 0.01 | 0.19 | 0.01 | 72.27 | 0.80 | 1.16 | 100.12 | 94.87 |
EXW | 22.83 | 0.06 | - | 1.02 | 1.30 | 0.26 | 0.01 | 0.07 | 0.05 | 71.61 | 0.88 | 2.32 | 100.40 | 95.46 |
BFN | 17.04 | 0.06 | - | 0.86 | 2.88 | 0.43 | 0.01 | 0.26 | 0.02 | 76.80 | 0.72 | 0.74 | 99.82 | 94.7 |
Limestone | 0.03 | 55.22 | - | 0.05 | - | 1.35 | 0.01 | 0.00 | 0.01 | 0.46 | - | 42.85 | 99.97 |
Quartz % | Muscovite % | Kaolinite % | Amorphous % | ||
---|---|---|---|---|---|
Raw clay | BFN | 81.99 | 18.01 | 0 | |
EXW | 66.39 | 6.42 | 27.19 | ||
MFN | 77.09 | 16.08 | 6.83 | ||
Calcined clay | BFN | 60 | 7 | 0 | 33 |
EXW | 54.3 | 1.6 | 13.2 | 30.9 | |
MFN | 56.1 | 8.8 | 5.7 | 29.3 |
Alite | Belite | Ferrite | Aluminate | Sulphates | Gypsum | Bassanite | Calcite | Quartz |
---|---|---|---|---|---|---|---|---|
C3S | C2S | C4AF | C3A | (K, Na)2SO4 | CaSO4.2H2O | 2CaSO4.H2O | CaCO3 | SiO2 |
75.7 | 0 | 4.86 | 1.26 | 0.14 | 0.07 | 0.72 | 16.11 | 1.21 |
Elements (%) | O | Mg | Al | Si | Cl | K | Fe |
---|---|---|---|---|---|---|---|
EXW | 72.208 | 0.184 | 8.58 | 14.354 | 0.272 | 1.904 | 1.01 |
BFN | 73.4275 | 0 | 10.475 | 15.4175 | 0.22 | 0.4175 | 0 |
MFN | 65.3775 | 0.34 | 8.055 | 13.2325 | 0.05 | 0.5925 | 0.66 |
Quartz SiO2 (%) | Calcite CaCO3 (%) | Portlandite Ca(OH)2 (%) | Alite (Ca3SiO5) (%) | Ettringite Al2Ca6H12O24S3 (%) | Amorphous Phases (%) | |
---|---|---|---|---|---|---|
PC | 60.2 | 1.9 | 0.9 | 2.8 | 0 | 34.2 |
BFN | 63 | 3.4 | 0.8 | 0.8 | 0.3 | 31.7 |
MFN | 69.1 | 2.9 | 0.6 | 0.6 | 0.5 | 26.3 |
EXW | 0 | 4.86 | 1.26 | 0.14 | 0.07 | 0.72 |
Relative Superplasticiser Content % | Mini-Slump (mm) | |
---|---|---|
PC | 100 | 190 |
EXW | 110 | 189 |
BFN | 180 | 191 |
MFN | 180 | 188 |
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Babafemi, A.J.; Knobel, H.; Kolawole, J.T.; Oyebanjo, O.M.; Bukalo, N.N.; Paul, S.C.; Miah, M.J. Performance of Selected South African Kaolinitic Clays for Limestone Calcined Clay Cement. Appl. Sci. 2022, 12, 10751. https://doi.org/10.3390/app122110751
Babafemi AJ, Knobel H, Kolawole JT, Oyebanjo OM, Bukalo NN, Paul SC, Miah MJ. Performance of Selected South African Kaolinitic Clays for Limestone Calcined Clay Cement. Applied Sciences. 2022; 12(21):10751. https://doi.org/10.3390/app122110751
Chicago/Turabian StyleBabafemi, Adewumi John, Hendrick Knobel, John Temitope Kolawole, Olaonipekun Moses Oyebanjo, Nenita Ntumba Bukalo, Suvash Chandra Paul, and Md Jihad Miah. 2022. "Performance of Selected South African Kaolinitic Clays for Limestone Calcined Clay Cement" Applied Sciences 12, no. 21: 10751. https://doi.org/10.3390/app122110751
APA StyleBabafemi, A. J., Knobel, H., Kolawole, J. T., Oyebanjo, O. M., Bukalo, N. N., Paul, S. C., & Miah, M. J. (2022). Performance of Selected South African Kaolinitic Clays for Limestone Calcined Clay Cement. Applied Sciences, 12(21), 10751. https://doi.org/10.3390/app122110751