Geopolymers: Synthesis, Characterization and Applications II

Abstract submission deadline

closed (29 February 2024)

Manuscript submission deadline

closed (30 April 2024)

Viewed by

7698

Topic Information

Dear Colleagues,

This proposed Interdisciplinary Topic is a continuation of the successful Special Issue “Geopolymers” in Minerals in 2018 and Interdisciplinary Topic “Geopolymers: Synthesis, Characterization and Applications” in 2021. Since its closure in September 2022, the 25 publications in the aforementioned Interdisciplinary Topic have had over 35000 views. Encouraged by the interest shown by readers, MDPI has decided to propose a second edition.

The term “geopolymer” was introduced in the early 1970s by Joseph Davidovits for inorganic polymeric materials, synthesized (by him) from natural (geo-) silicon and aluminum-containing sources, reacted with alkaline media (solvent). Geopolymers consist of repeating siloxonate (Na, K, Ca) (-Si-O-Si-O-) or sialate (Na, K, Ca) (-Si-O-Al-O-) units (oligomers), polycondensed into typically ceramic, covalently bounded, non-crystalline (amorphous) 3D networks. Further research widened their definition by adding ferro-sialate and alumino-phosphate oligomers, as well as acidic (using phosphoric or humic acids as solvent) geopolymerization routes.

The scientific interest in this innovative class of materials is driven by three main factors:

1. A series of features, making geopolymers applicable and even preferred for many industrial applications, including but not limited to:

• Geopolymer resins and binders;
• Geopolymer cements and concretes:
  • Low-tech building materials (geopolymer bricks, blocks and other cast elements);
  • Low-CO₂ cements and concretes.
• Fixing of potentially hazardous chemicals in water resistant (insoluble) geopolymers.

2. The possibility of employing in their synthesis a number of inorganic industrial waste products, such as blast furnace slags, thermal power plant fly-ash, mine tailings, etc., some of which are abundantly available all over the world.

3. Environmentally friendly industrial production. The use of industrial waste can enormously enhance the resource efficiency of industrial branches generating such waste, such as mining or metallurgy. On the other hand, the use of already-existing waste material can significantly diminish large waste dumps, directly improving the environmental status of affected areas.

4. The possible replacement (even partial) of ordinary cements and concretes by geopolymers (produced by carbon-free sources) is also a route to low-carbon production, diminishing the industrial tension on climate change.

In order to cover a wider area of geo-waste utilization, in this second edition, we aim to enhance the strict geopolymerization with studies on alkali activation and vitrification.

Considering the interdisciplinary character of the topic, we are launching it across a wider range of MDPI journals, in the hope of attracting papers that cover this subject from different points of view.

Prof. Dr. Thomas N. Kerestedjian
Prof. Dr. Alexander Karamanov
Topic Editors

Keywords

Participating Journals

Journal Name	Impact Factor	CiteScore	Launched Year	First Decision (median)	APC
Ceramics ceramics	2.7	3.0	2018	25.2 Days	CHF 1600
Construction Materials constrmater	-	-	2021	24.3 Days	CHF 1000
Geotechnics geotechnics	-	-	2021	16.9 Days	CHF 1000
Materials materials	3.1	5.8	2008	15.5 Days	CHF 2600
Minerals minerals	2.2	4.1	2011	18 Days	CHF 2400

MDPI Topics is cooperating with Preprints.org and has built a direct connection between MDPI journals and Preprints.org. Authors are encouraged to enjoy the benefits by posting a preprint at Preprints.org prior to publication:

1. Immediately share your ideas ahead of publication and establish your research priority;
2. Protect your idea from being stolen with this time-stamped preprint article;
3. Enhance the exposure and impact of your research;
4. Receive feedback from your peers in advance;
5. Have it indexed in Web of Science (Preprint Citation Index), Google Scholar, Crossref, SHARE, PrePubMed, Scilit and Europe PMC.

Published Papers (7 papers)

Order results

Content type Publication Date

Result details

Normal Extended Compact

Journals

All Ceramics Construction Materials Geotechnics Materials Minerals

Show export options expand_more Show export options expand_less

Select all

Export citation of selected articles as:

Plain Text BibTeX BibTeX (without abstracts) Endnote Endnote (without abstracts) Tab-delimited RIS

Error

Oops... you haven't selected anything for export.

Ok

clear

16 pages, 2964 KiB  

Open AccessArticle

Towards Safe Diatomite Sludge Management: Lead Immobilisation via Geopolymerisation

by Haozhe Guo, Zhihao Huang, Baifa Zhang, Ting Yu, Thammaros Pantongsuk and Peng Yuan

Minerals 2024, 14(8), 763; https://doi.org/10.3390/min14080763 - 27 Jul 2024

Viewed by 949

Abstract

Diatomite, a natural adsorbent rich in active silica, serves as a valuable precursor for geopolymer synthesis. The safe disposal of diatomite as a failed lead (Pb(II)) adsorbent is critical to prevent secondary contamination. This study investigated the immobilisation efficiency of geopolymerisation for Pb(II)-rich [...] Read more.

Diatomite, a natural adsorbent rich in active silica, serves as a valuable precursor for geopolymer synthesis. The safe disposal of diatomite as a failed lead (Pb(II)) adsorbent is critical to prevent secondary contamination. This study investigated the immobilisation efficiency of geopolymerisation for Pb(II)-rich diatomite sludge. Low-grade diatomite with high ignition loss was utilised in the synthesis of alkali-activated geopolymers. It was demonstrated that the geopolymers achieved a compressive strength of 28.3 MPa with a 50% replacement rate of metakaolin by diatomite sludge, which was not a compromise in strength compared to that of the geopolymer with no Pb(II) (26.2 MPa). The leaching behaviour of Pb(II) was evaluated using water and acetic acid, yielding concentrations below 3 mg/L and immobilisation efficiencies of 95% in both scenarios. Analytical techniques including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) elucidated the mineral composition and chemical environment of the geopolymers. These analyses revealed that Pb(II) migrated from diatomite pores, potentially forming soluble hydroxides under sufficient hydroxide, which then participated in condensation with silicon and aluminium monomers, effectively immobilising Pb(II) within amorphous aluminosilicate gels. Furthermore, the formation of the amorphous gels within diatomite pores hindered Pb(II) leaching, encapsulating Pb(II) effectively. This study presents a novel approach to immobilising heavy metals within building materials, enhancing mineral resource utilisation efficiency while addressing environmental contamination concerns. Full article

(This article belongs to the Topic Geopolymers: Synthesis, Characterization and Applications II)

►▼ Show Figures

Figure 1

13 pages, 4358 KiB  

Open AccessArticle

Synthesis of Geopolymers Incorporating Mechanically Activated Fly Ash Blended with Alkaline Earth Carbonates: A Comparative Analysis

by Alexander M. Kalinkin, Elena V. Kalinkina, Ekaterina A. Kruglyak and Alla G. Ivanova

Minerals 2024, 14(7), 726; https://doi.org/10.3390/min14070726 - 19 Jul 2024

Viewed by 864

Abstract

The objective of this study is to perform a comparative analysis of the impact of incorporating alkaline earth metal carbonates (MCO₃, where M–Mg, Ca, Sr, Ba) into low-calcium fly ash (FA) on the geopolymerization processes and the resultant properties of composite [...] Read more.

The objective of this study is to perform a comparative analysis of the impact of incorporating alkaline earth metal carbonates (MCO₃, where M–Mg, Ca, Sr, Ba) into low-calcium fly ash (FA) on the geopolymerization processes and the resultant properties of composite geopolymers. Mechanical activation was employed to enhance the reactivity of the mixtures. The reactivity of the mechanically activated (FA + alkaline earth carbonate) blends towards NaOH solution was experimentally studied using XRD analysis and FTIR spectroscopy. In agreement with thermodynamic calculations, MgCO₃ demonstrated the most active interaction with the alkaline solution, whereas strontium and barium carbonates exhibited little to no chemical interaction, and calcite was situated in the transition region. As the calcite content in the mixture with FA increased, the compressive strength of the geopolymers continuously improved. The addition of Mg, Sr, and Ba carbonates to the FA did not enhance the strength of geopolymers. However, the strength of geopolymers based on these blends was comparable with that of geopolymers based on 100% FA. The strength of geopolymers synthesized from the 100% FA and from the (90% FA + 10% MCO₃) blends, mechanically activated for 180 s, at the age of 180 days was 11.0 MPa (0% carbonate), 11.1 MPa (10% MgCO₃), 36.5 MPa (10% CaCO₃), 13.6 MPa (10% SrCO₃), and 12.4 MPa (10% BaCO₃) MPa, respectively. The influence of carbonate additives on the properties of the composite geopolymers was examined, highlighting filler, dilution, and chemical effects. The latter determined the unique position of calcite among the carbonates of alkaline earth metals. Full article

(This article belongs to the Topic Geopolymers: Synthesis, Characterization and Applications II)

►▼ Show Figures

Figure 1

attachment

Supplementary material:
Supplementary File 1 (ZIP, 4867 KiB)

24 pages, 7794 KiB  

Open AccessArticle

Effect of Water-Soluble Polymers on the Rheology and Microstructure of Polymer-Modified Geopolymer Glass-Ceramics

by John M. Migliore, Patrick Hewitt, Theo J. Dingemans, Davide L. Simone and William Jacob Monzel

Materials 2024, 17(12), 2856; https://doi.org/10.3390/ma17122856 - 11 Jun 2024

Viewed by 1082

Abstract

This work explores the effects of rigid (0.1, 0.25, and 0.5 wt. %) and semi-flexible (0.5, 1.0, and 2.5 wt. %) all-aromatic polyelectrolyte reinforcements as rheological and morphological modifiers for preparing phosphate geopolymer glass–ceramic composites. Polymer-modified aluminosilicate–phosphate geopolymer resins were prepared by high-shear [...] Read more.

This work explores the effects of rigid (0.1, 0.25, and 0.5 wt. %) and semi-flexible (0.5, 1.0, and 2.5 wt. %) all-aromatic polyelectrolyte reinforcements as rheological and morphological modifiers for preparing phosphate geopolymer glass–ceramic composites. Polymer-modified aluminosilicate–phosphate geopolymer resins were prepared by high-shear mixing of a metakaolin powder with 9M phosphoric acid and two all-aromatic, sulfonated polyamides. Polymer loadings between 0.5–2.5 wt. % exhibited gel-like behavior and an increase in the modulus of the geopolymer resin as a function of polymer concentration. The incorporation of a 0.5 wt. % rigid polymer resulted in a three-fold increase in viscosity relative to the control phosphate geopolymer resin. Hardening, dehydration, and crystallization of the geopolymer resins to glass-ceramics was achieved through mold casting, curing at 80 °C for 24 h, and a final heat treatment up to 260 °C. Scanning electron microscopy revealed a decrease in microstructure porosity in the range of 0.78 μm to 0.31 μm for geopolymer plaques containing loadings of 0.5 wt. % rigid polymer. Nano-porosity values of the composites were measured between 10–40 nm using nitrogen adsorption (Brunauer–Emmett–Teller method) and transmission electron microscopy. Nanoindentation studies revealed geopolymer composites with Young’s modulus values of 15–24 GPa and hardness values of 1–2 GPa, suggesting an increase in modulus and hardness with polymer incorporation. Additional structural and chemical analyses were performed via thermal gravimetric analysis, Fourier transform infrared radiation, X-ray diffraction, and energy dispersive spectroscopy. This work provides a fundamental understanding of the processing, microstructure, and mechanical behavior of water-soluble, high-performance polyelectrolyte-reinforced geopolymer composites. Full article

(This article belongs to the Topic Geopolymers: Synthesis, Characterization and Applications II)

►▼ Show Figures

Figure 1

15 pages, 13322 KiB  

Open AccessArticle

Evaluating the Performance of Class F Fly Ash Compared to Class G Cement for Hydrocarbon Wells Cementing: An Experimental Investigation

by Youssef Helmy and Sherif Fakher

Materials 2024, 17(11), 2710; https://doi.org/10.3390/ma17112710 - 3 Jun 2024

Cited by 4 | Viewed by 501

Abstract

The following study presents the results of research in the field of the performance of geopolymers consisting of Class F fly ash with an alkaline activator solution consisting only of sodium metasilicate (Na₂SiO₃) and water. The performances of this [...] Read more.

The following study presents the results of research in the field of the performance of geopolymers consisting of Class F fly ash with an alkaline activator solution consisting only of sodium metasilicate (Na₂SiO₃) and water. The performances of this geopolymer are compared to the those of American Petroleum Institute (API) Class G cement. This comparison is to evaluate the potential of the geopolymer as an alternative to cement in cementing hydrocarbon wells in the oil and gas industry. The gap in the research is determining the performance properties that restrict the use of fly ash in the oil and gas industry. Using only sodium metasilicate as an activator with water, the solution creates a strong binding gel for the geopolymer and activates the aluminosilicate properties of the fly ash. This geopolymer is compared with Class G cement without additives to determine their base performances in high pressure and high temperature conditions, as well as note any properties that are affected in the process. This commences by formulating recipes of these two materials from workable ratios and concentrations. The ratios are narrowed down to the best working models to proceed to comparative performance testing. The tests included exploring their vital performances in fluid loss and thickening time. The results produced suggest that Class G cement generally has less fluid loss at low temperature than the geopolymer but could not maintain its integrity and structure as temperatures increased. Class G cement exhibited stability, consistencies of 100 Bcs (Bearden Consistency Units), and a faster thickening time of 1 h and 48 min when placed under high temperature and high-pressure conditions, respectively. However, the geopolymer showed more consistency regarding fluid loss with respect to rising pressure and temperature, and smoother, less fractured samples emerging from both tests. Though the geopolymer showed stronger performances in thickening and water retention, the experiments showed that it is not a uniform and consistent material like Class G cement. Through the use of different additives and intricate design, the sample may show success, but may prove more difficult and complex to apply than the industry standard and uniform content of Class G cement. Full article

(This article belongs to the Topic Geopolymers: Synthesis, Characterization and Applications II)

►▼ Show Figures

Figure 1

17 pages, 5358 KiB  

Open AccessArticle

Experimental Study on Geopolymerization of Lunar Soil Simulant under Dry Curing and Sealed Curing

by Jinhui Gu and Qinyong Ma

Materials 2024, 17(6), 1413; https://doi.org/10.3390/ma17061413 - 20 Mar 2024

Viewed by 1025

Abstract

The construction of lunar surface roads is conducive to improving the efficiency of lunar space transportation. The use of lunar in situ resources is the key to the construction of lunar bases. In order to explore the strength development of a simulated lunar [...] Read more.

The construction of lunar surface roads is conducive to improving the efficiency of lunar space transportation. The use of lunar in situ resources is the key to the construction of lunar bases. In order to explore the strength development of a simulated lunar soil geopolymer at lunar temperature, geopolymers with different sodium hydroxide (NaOH) contents were prepared by using simulated lunar regolith materials. The temperature of the high-temperature section of the moon was simulated as the curing condition, and the difference in compressive strength between dry curing and sealed curing was studied. The results show that the high-temperature range of lunar temperature from 52.7 °C to 76.3 °C was the suitable curing period for the geopolymers, and the maximum strength of 72 h was 6.31 MPa when the NaOH content was 8% in the sealed-curing mode. The 72 h strength had a maximum value of 6.87 MPa when the NaOH content was 12% under dry curing. Choosing a suitable solution can reduce the consumption of activators required for geopolymers to obtain unit strength, effectively reduce the quality of materials transported from the Earth for lunar infrastructure construction, and save transportation costs. The microscopic results show that the simulated lunar soil generated gel substances and needle-like crystals under the alkali excitation of NaOH, forming a cluster and network structure to improve the compressive strength of the geopolymer. Full article

(This article belongs to the Topic Geopolymers: Synthesis, Characterization and Applications II)

►▼ Show Figures

Figure 1

23 pages, 4063 KiB  

Open AccessArticle

Effect of Microwaves on the Rapid Curing of Metakaolin- and Aluminum Orthophosphate-Based Geopolymers

by Jasmine Aschoff, Stephan Partschefeld, Jens Schneider and Andrea Osburg

Materials 2024, 17(2), 463; https://doi.org/10.3390/ma17020463 - 18 Jan 2024

Viewed by 1090

Abstract

This paper deals with the influence of microwaves on the hardening and curing of geopolymer binders synthesized from metakaolin or aluminum orthophosphate with sodium silicate solution as the activator. Pure geopolymer pastes as well as geopolymer mortars were considered. The variable parameters were [...] Read more.

This paper deals with the influence of microwaves on the hardening and curing of geopolymer binders synthesized from metakaolin or aluminum orthophosphate with sodium silicate solution as the activator. Pure geopolymer pastes as well as geopolymer mortars were considered. The variable parameters were the modulus of the sodium silicate solutions (molar ratio of SiO₂ to Na₂O: 1.5, 2.0 and 2.5) and the Si/Al ratio (3/1 and 2/1). Selected samples were cured in a microwave oven until hardening, so the curing time depended on the mixture. For comparison some samples were cured at ambient temperature. To investigate the influence of microwave radiation on the reaction kinetics, isothermal heat flow calorimetry, ultrasonic velocity measurements and rheological investigations into the variation of curing temperature were used. In addition, the mechanical properties of the cured samples were characterized. The results show that microwave curing only takes a few minutes, so it is the most time-saving method. Key factors influencing the geopolymer reaction under microwave radiation are the raw materials as well as the Si/Al ratio. Metakaolin-based geopolymer binders are more stable than those based on aluminum orthophosphate, especially regarding their salt efflorescence. Microwave radiation is an efficient method to accelerate the geopolymer reaction. Full article

(This article belongs to the Topic Geopolymers: Synthesis, Characterization and Applications II)

►▼ Show Figures

Figure 1

14 pages, 7642 KiB  

Open AccessArticle

Effective Stabilization of Cadmium and Copper in Iron-Rich Laterite-Based Geopolymers and Influence on Physical Properties

by Rachel Yanou Nkwaju, Joëlle Nadia Fekoua Nouping, Soumayah Bachirou, Tatiane Marina Abo, Juvenal Giogetti Nemaleu Deutou and Jean Noël Yankwa Djobo

Materials 2023, 16(24), 7605; https://doi.org/10.3390/ma16247605 - 12 Dec 2023

Cited by 1 | Viewed by 959

Abstract

This study aimed to investigate the efficiency of a geopolymer binder of the type of Na-poly(ferro–silico–aluminate) as a matrix for the stabilization of heavy metals along with their effect on the development of structural performances. The artificial contamination of soil with ions was [...] Read more.

This study aimed to investigate the efficiency of a geopolymer binder of the type of Na-poly(ferro–silico–aluminate) as a matrix for the stabilization of heavy metals along with their effect on the development of structural performances. The artificial contamination of soil with ions was carried out and used to prepare an alkali-activated iron-rich lateritic soil binder. Further, various microstructural analyses were carried out to explain the stabilization mechanism. The stabilization efficiency was assessed by leaching tests in de-ionized water and hydrochloric acid (0.1 M, HCl). Then, the physical properties were determined to evaluate the impact of heavy metals on the structural performance of the binder. Results demonstrated that the prepared geopolymer binder has the lowest stabilization capacity in an acidic medium (low pH) than in water with high pH. However, the stabilization of Cu ions was effective at 99%, while the Cd ion is barely retained in the matrix. Firstly, the mechanism consists of chemical bonds through ion exchange with sodium of the Na-poly(ferro–silico–aluminate) network. Secondly, through physical interaction with the pore network of the matrix, the heavy metals induced structural deterioration in the geopolymer matrix with a decrease in the compressive strength and bulk density and an increase of both apparent porosity and water absorption. Full article

(This article belongs to the Topic Geopolymers: Synthesis, Characterization and Applications II)

►▼ Show Figures

Figure 1

Show export options expand_more Show export options expand_less

Select all

Export citation of selected articles as:

Plain Text BibTeX BibTeX (without abstracts) Endnote Endnote (without abstracts) Tab-delimited RIS

 

Error

Oops... you haven't selected anything for export.

Ok

clear

Displaying articles 1-7