Aggregates Obtained by Alkali Activation of Fly Ash: The Effect of Granulation, Pelletization Methods and Curing Regimes
Abstract
:1. Introduction
2. Materials and Methods
2.1. Raw Materials
2.2. Mix design
2.3. Paste Preparation and the Creation of Aggregate by Crushing
2.4. Paste Preparation and the Creation of Aggregate by Pelletization
2.5. Curing Regimes and Labelling
2.6. Experimental Procedures and Techniques
3. Results and Discussion
3.1. Physical Properties of Aggregates
3.2. Mineralogical and Structural Characterization of FA and Alkali Activated Fly Ash Aggregates
3.3. BSE-EDS Analysis
3.4. Textural Properties
4. Conclusions
- FTIR analyses showed that the greatest changes occurred in the amorphous phase in both types of aggregate. FTIR analyses indicated a better dilution of fly ash in the aggregate obtained by crushing compared to the aggregate obtained by pelletization of what was confirmed by the changes in FTIR peak positions. Polymerization was most pronounced for the aggregates exposed to 65 °C for 5 days.
- FTIR analyses also showed that the process of carbonation occurred upon alkali activation across all investigated aggregate samples, this being more pronounced in the case of the aggregate obtained by pelletization in comparison to the aggregate obtained by the crushing method. Since the process of carbonation decreases pH value, it is presumed that the N-A-S-H structure of Gel 2 was probably formed at a low pH.
- The XRD analyses showed that neither the granulation method nor the curing conditions had a great influence on crystal phase composition. BSE-EDS analyses indicated that the structures obtained by pelletization contained phases developed during the incongruent dissolution of the parent material (silica and alumina phases), in addition to incompletely dissolved grains from the alkali-activated fly ash matrix.
- The Si/Al atomic ratio was greater in the aggregate obtained by crushing than in that formed by pelletization. The lower Si/Al atomic ratio observed in the VC samples could be the result of two things: a higher activator/fly ash ratio value on the granule surface, indicating an increase in silicon concentration, and the decrease in pH value due to carbonation.
- The total porosity values were lower for the samples cured in normal conditions for 28 and 120 days in comparison to those cured at 65 °C. Pore size distribution was correlated to the amount of gel and the curing regime; exposure to an elevated temperature led to a higher ratio of pores smaller than 0.5 μm in both types of aggregates. Conversely, curing under normal conditions for 120 days led to the creation of larger pores.
Author Contributions
Funding
Conflicts of Interest
References
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SiO2 | Al2O3 | Fe2O3 | SO3 | CaO | MgO | Na2O | K2O | Cl− | SiO2r 1 | LOI |
---|---|---|---|---|---|---|---|---|---|---|
56.1 | 19.7 | 5.36 | 3.1 | 6.95 | 1.83 | 0.60 | 2.05 | 0.007 | 37.34 | 4.28 |
Aggregate | Oven Dried Particle Density, kg/m3 | Apparent Particle Density, kg/m3 | Water Absorption after 24 h, % |
---|---|---|---|
GP 5 | 1495 | 2585 | 28.2 |
GP 28 | 1490 | 2526 | 27.5 |
GP 120 | 1492 | 2530 | 26.0 |
VC 5 | 1470 | 2400 | 26.4 |
VC 28 | 1348 | 2570 | 35.3 |
VC 120 | 1450 | 2350 | 26.5 |
FA | GP 5 | GP 28 | GP 120 | VC 5 | VC 28 | VC 120 |
---|---|---|---|---|---|---|
Absorption peak position (cm−1) | ||||||
873 | 881 | 872 | 872 | 872 | 881 | |
902 | 902 | |||||
952 | 953 | 953 | 957 | 929 | 940 | 959 |
975 | ||||||
1023 | 1027 | 1021 | 1034 | 1017 | 996 | 1006 |
1041 | 1053 | 1041 | 1051 | |||
1093 | 1093 | 1083 | 1089 | 1089 | 1089 | 1089 |
1121 | 1127 | 1114 | 1113 | 1125 | 1125 | 1125 |
1136 | 1136 | |||||
1159 | 1160 | 1150 | 1153 | 1153 | 1153 | 1152 |
1171 | ||||||
1183 | 1178 | 1186 | 1175 | 1182 | 1182 | 1176 |
Sample | Slope of the Linear Curve Si/Al |
---|---|
GP 5 | 2.94 |
GP 28 | 2.41 |
GP 120 | 2.51 |
VC 5 | 1.88 |
VC 28 | 1.93 |
VC 120 | 1.95 |
Sample | Total Porosity (%) |
---|---|
GP 5 | 36.1 |
GP 28 | 17.4 |
GP 120 | 12.9 |
VC 5 | 34.6 |
VC 28 | 40.2 |
VC 120 | 29.2 |
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Rudić, O.; Ducman, V.; Malešev, M.; Radonjanin, V.; Draganić, S.; Šupić, S.; Radeka, M. Aggregates Obtained by Alkali Activation of Fly Ash: The Effect of Granulation, Pelletization Methods and Curing Regimes. Materials 2019, 12, 776. https://doi.org/10.3390/ma12050776
Rudić O, Ducman V, Malešev M, Radonjanin V, Draganić S, Šupić S, Radeka M. Aggregates Obtained by Alkali Activation of Fly Ash: The Effect of Granulation, Pelletization Methods and Curing Regimes. Materials. 2019; 12(5):776. https://doi.org/10.3390/ma12050776
Chicago/Turabian StyleRudić, Ognjen, Vilma Ducman, Mirjana Malešev, Vlastimir Radonjanin, Suzana Draganić, Slobodan Šupić, and Miroslava Radeka. 2019. "Aggregates Obtained by Alkali Activation of Fly Ash: The Effect of Granulation, Pelletization Methods and Curing Regimes" Materials 12, no. 5: 776. https://doi.org/10.3390/ma12050776
APA StyleRudić, O., Ducman, V., Malešev, M., Radonjanin, V., Draganić, S., Šupić, S., & Radeka, M. (2019). Aggregates Obtained by Alkali Activation of Fly Ash: The Effect of Granulation, Pelletization Methods and Curing Regimes. Materials, 12(5), 776. https://doi.org/10.3390/ma12050776