Development of Geopolymers Based on Fly Ashes from Different Combustion Processes

Pławecka, Kinga; Bazan, Patrycja; Lin, Wei‐Ting; Korniejenko, Kinga; Sitarz, Maciej; Nykiel, Marek

doi:10.3390/polym14101954

Cited by 16 publications

(11 citation statements)

References 65 publications

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“…Compared with ordinary Portland cement, geopolymers have excellent properties such as acid resistance, alkali resistance, impermeability, frost resistance and high-temperature resistance [ 19 , 20 , 21 , 22 ]. However, since the hydration products of geopolymers do not contain Ca(OH) 2 as a buffer, their carbonation resistance is much lower than that of ordinary silicate concrete [ 23 , 24 ]. The carbonization resistance of geopolymer is a key factor affecting its durability and is an urgent problem to be solved.…”

Section: Introductionmentioning

confidence: 99%

Modification Effect of Ca(OH)2 on the Carbonation Resistance of Fly Ash-Metakaolin-Based Geopolymer

Qiao

Han

et al. 2023

Materials

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Compared with Portland cement, geopolymers have poor carbonization resistance, which will greatly limit the application their application. To improve the carbonization resistance of geopolymers, firstly, the carbonization behavior of the fly ash-metakaolin-based geopolymer was studied through accelerated carbonization tests. Secondly, different amounts of Ca(OH)2 were introduced into the composite system, and the modification effect of the carbonization resistance of the modified geopolymer was studied. Finally, the modification effect of Ca(OH)2 on the fly ash-metakaolin-based geopolymers was analyzed, and the modification mechanism was explored. It was found that adding Ca(OH)2 to the fly ash-metakaolin-based geopolymer could significantly improve its initial compressive strength, but its strength after carbonization remained basically unchanged; meanwhile, the compressive strength of the terpolymer after carbonization clearly decreased after adding Ca(OH)2. Compared with ordinary Portland cement, the carbonization rate of fly ash-metakaolin-based geopolymer is faster, and the addition of Ca(OH)2 can inhibit the development of its carbonization depth. With increased carbonization age, the alkalinity of the geopolymer decreased, and the addition of Ca(OH)2 inhibited the decrease in the alkalinity of the geopolymer. The addition of Ca(OH)2 improved the microstructure of the geopolymers, the pore structure became denser, and the pore size became smaller size after carbonization. The hydration products of fly ash-metakaolin-based geopolymer are mainly amorphous silicaluminate gel and C–S–H gel, and Ca(OH)2 forms in the hydration products of terpolymer with the incorporation of Ca(OH)2, which is conducive to improving the carbonization resistance. In summary, Ca(OH)2 can play a good role in modifying the carbonization resistance of fly ash-metakaolin-based geopolymers.

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Section: Introductionmentioning

confidence: 99%

Modification Effect of Ca(OH)2 on the Carbonation Resistance of Fly Ash-Metakaolin-Based Geopolymer

Qiao

Han

et al. 2023

Materials

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“…As a common precursor of geopolymer material, the compressive strength of geopolymers formed from different types of fly ash is related to the variation of fly ash in particle size distribution, chemical composition, morphological properties and amorphous phase [ 10 ]. It has been shown that the geopolymer made from ultrafine fly ash has a higher compressive strength than conventional fly ash, but the flexural strength is only one-twentieth of that of conventional fly ash geopolymer [ 11 ]. In addition, calcium in fly ash can promote the formation of C-S-H gels, and fly ash with high calcium content is more conducive to improving the strength of geopolymer [ 12 ], but the inadequacy of calcium fraction on the development of three-dimensional mesh structure of geopolymer restricts the application of high-calcium fly ash [ 13 ].…”

Section: Introductionmentioning

confidence: 99%

Mechanical Properties of Fly Ash-Slag Based Geopolymer for Repair of Road Subgrade Diseases

Dang

Zhang

et al. 2023

Polymers

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Fly ash-slag-based geopolymer is a grouting material with good fluidity and excellent mechanical and eco-friendly properties. The geopolymer can react chemically with the inert minerals of road subgrade under alkali excitation to form a good interfacial bond between road subgrade; therefore, it is suitable for the repair of weak road sections. In order to solve the problems such as the difficulty to store and transport the liquid activator of existing geopolymer grouting materials and to study the unclear mechanism of the influence factors on the fluidity and mechanical properties of geopolymer; the research on the mechanical properties of fly ash-slag based geopolymer was carried out in this paper. Experiments on the preparation of geopolymer and research on different ash-slag ratios under solid alkali excitation were studied. The influence of slag content and solid alkali content (NaOH, Na2SiO3) on the fluidity, compressive and flexural strength of fly ash-slag-based grouting materials was also researched on the basis of single-factor gradient tests. The results showed that the slurry fluidity decreased but the compressive strength gradually increased when the content of slag was increased from 20% to 50%. With the increase in alkali content (NaOH: 2–5%; sodium silicate: 0–6%), the slurry fluidity decreased and the compressive strength increased and then decreased. Combined with the analysis of the test results of Scanning Electron Microscopy (SEM), the microscopic structures of mechanical properties of geopolymer were investigated. Lastly based on ridge regression theory, a regression model was established to predict the mechanical properties of fly ash-slag-based geopolymer. The results indicate that fly ash-slag-based geopolymer has good mechanical properties and fluidity with proper contents of slag and alkali activator, which provide a reference for experiment research and engineering application.

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“…Cement serves as a concrete binder and creates stunning structures for human civilization, and simultaneously, its production process emits a large amount of CO 2 [ 1 , 2 , 3 ]. Cement production accounts for about 7% of the world’s CO 2 emissions [ 4 ]. In addition, 1700 kg of raw materials are consumed to make 1000 kg of clinker [ 5 ].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Oyster Shell Powder on the High-Temperature-Properties of Slag-Ceramic Powder-Based Geopolymer

et al. 2023

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There is a lack of scientific understanding of adding an oyster shell powder (OSP) to geopolymer concrete. The purpose of this study is: (1) to evaluate the high-temperature resistance of the alkali-activated slag ceramic powder (CP) mixture added with OSP at different temperatures, (2) to address the lack of application of environmentally friendly building materials, and (3) to reduce solid waste of OSP pollution and protect the environment. OSP replaces granulated blast furnace slag (GBFS) and CP at 10% and 20% (based on binder), respectively. The mixture was heated to 400.0, 600.0, and 800.0 °C after curing for 180 days. The results of the experiment are summarized as follows: (1) The thermogravimetric (TG) results indicated that the OSP20 samples produced more CASH gels than the control OSP0. (2) As the temperature increased, the compressive strength and ultrasonic pulse velocity (UPV) both decreased. (3) Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) results reveal that the mixture undergoes a phase transition at 800.0 °C, and compared with the control OSP0, OSP20 undergoes a different phase transition. (4) The size change and appearance image results indicate that the mixture with added OSP inhibits shrinkage, and calcium carbonate decomposes to produce off-white CaO. To sum up, adding OSP can effectively reduce the damage of high temperatures (800.0 °C) on the properties of alkali-activated binders.

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Development of Geopolymers Based on Fly Ashes from Different Combustion Processes

Cited by 16 publications

References 65 publications

Modification Effect of Ca(OH)2 on the Carbonation Resistance of Fly Ash-Metakaolin-Based Geopolymer

Modification Effect of Ca(OH)2 on the Carbonation Resistance of Fly Ash-Metakaolin-Based Geopolymer

Mechanical Properties of Fly Ash-Slag Based Geopolymer for Repair of Road Subgrade Diseases

The Effect of Oyster Shell Powder on the High-Temperature-Properties of Slag-Ceramic Powder-Based Geopolymer

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