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Geopolymers: Recent Research and Future Prospect

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A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Applications".

Deadline for manuscript submissions: closed (31 January 2024) | Viewed by 8344

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Special Issue Editor

Dr. Laura Ricciotti

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Guest Editor

Department of Architecture and Industrial Design, University of Campania, Luigi Vanvitelli, 81031 Aversa, Italy
Interests: geopolymers; polymers; functional materials; sustainable materials; life cycle assessment (LCA); additive manufacturing; mechanical properties; chemical-physical characterizations
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Geopolymers are amorphous ceramic materials obtained from the alkaline activation of aluminosilicates, including those derived from wastes. They can help to reduce the energy consumption during production, the emission of greenhouse gases, and the environmental impacts if compared to ordinary Portland cement-based materials. The application fields of geopolymers can be divided into two main categories: those with conventional physical and mechanical properties, and those for functional and advanced applications.

Geopolymers belonging to the first category can find applications in building, construction, repair, restoring, marine construction, pavement base materials, 3D printing, fire-resistant and high-temperature materials, and thermal and acoustic insulation. Special applications include the immobilization of heavy metal pollution, pH regulator materials, catalysts, conductive materials for moisture sensor applications, and thermal storage.

Functional applications, such as in fire prevention, isolation, heat preservation, and adsorption of harmful ions, can be used for buildings in special fields. These range from such examples as fire prevention buildings, insulation walls, biomaterials, and nuclear power plants.

We are pleased to invite expert submissions in the field of geopolymers for inclusion in this Special Issue.

You may choose our Joint Special Issue in Materials.

Dr. Laura Ricciotti
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

geopolymer
alkali activated materials
sustainable materials
composite
hybrid
art and design
restoration
biomaterials
foamed materials
additive manufacturing

Published Papers (4 papers)

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Research

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25 pages, 4106 KiB

Open AccessArticle

Improvements in Hydrolytic Stability of Alkali-Activated Mine Tailings via Addition of Sodium Silicate Activator

by Cara Clements, Lori Tunstall, Hector Gelber Bolanos Sosa and Ahmadreza Hedayat

Polymers 2024, 16(7), 957; https://doi.org/10.3390/polym16070957 - 31 Mar 2024

Viewed by 461

Abstract

Over 14 billion tons of mine tailings are produced throughout the world each year, and this type of waste is generally stored onsite indefinitely. Alkali activation is a promising strategy for the reuse of mine tailings to produce construction materials, converting this waste stream into a value-added product. One major problem with alkali-activated mine tailings is their low durability in water (i.e., low hydrolytic stability). In this article, the influence of a mixed sodium hydroxide/sodium silicate alkali activator on the compressive strength, hydrolytic stability, and microstructure of alkali-activated materials (AAMs) were systematically investigated. XRD, FTIR, NMR, and NAD were used to investigate microstructural changes, and a water immersion test was used to show improvements in hydrolytic stability. For gold mine tailings activated with pure sodium hydroxide, the compressive strength was 15 MPa and a seven-day water immersion test caused a strength loss of 70%. With an addition of 1 M sodium silicate in the activator, the AAMs achieved a compressive strength of over 30 MPa and strength loss of only 45%. This paper proposes a mechanism explaining why the strength and hydrolytic stability of AAMs are dependent on the dosage of soluble silicate. A high dosage of sodium silicate inhibits the depolymerization of the source material, which results in a sample with less amorphous aluminosilicate gel and, therefore, lower hydrolytic stability. Full article

(This article belongs to the Special Issue Geopolymers: Recent Research and Future Prospect)

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17 pages, 4217 KiB

Open AccessArticle

Study of the Mechanical Properties and Microstructure of Alkali-Activated Fly Ash–Slag Composite Cementitious Materials

by Yigang Lv, Cui Wang, Weiwei Han, Xing Li and Hui Peng

Polymers 2023, 15(8), 1903; https://doi.org/10.3390/polym15081903 - 15 Apr 2023

Cited by 7 | Viewed by 1546

Abstract

Composites that use fly ash and slag as alkali-activated materials instead of cement can overcome the defects and negative effects of alkali-activated cementitious materials prepared with the use of an alkali-activated material. In this study, fly ash and slag were used as raw materials to prepare alkali-activated composite cementitious materials. Experimental studies were carried out on the effects of the slag content, activator concentration and curing age on the compressive strength of the composite cementitious materials. The microstructure was characterized using hydration heat, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM), and its intrinsic influence mechanism was revealed. The results show that increasing the curing age improves the degree of polymerization reaction and the composite reaches 77~86% of its 7-day compressive strength after 3 days. Except for the composites with 10% and 30% slag content, which reach 33% and 64%, respectively, of their 28-day compressive strength at 7 days, the remaining composites reach more than 95%. This result indicates that the alkali-activated fly ash–slag composite cementitious material has a rapid hydration reaction in the early stage and a slow hydration reaction in the later stage. The amount of slag is the main influencing factor of the compressive strength of alkali-activated cementitious materials. The compressive strength shows a trend of continuous increase when increasing slag content from 10% to 90%, and the maximum compressive strength reaches 80.26 MPa. The increase in the slag content introduces more Ca²⁺ into the system, which increases the hydration reaction rate, promotes the formation of more hydration products, refines the pore size distribution of the structure, reduces the porosity, and forms a denser microstructure. Therefore, it improves the mechanical properties of the cementitious material. The compressive strength shows a trend of first increasing and then decreasing when the activator concentration increases from 0.20 to 0.40, and the maximum compressive strength is 61.68 MPa (obtained at 0.30). The increase in the activator concentration improves the alkaline environment of the solution, optimizes the level of the hydration reaction, promotes the formation of more hydration products, and makes the microstructure denser. However, an activator concentration that is too large or too small hinders the hydration reaction and affects the strength development of the cementitious material. Full article

(This article belongs to the Special Issue Geopolymers: Recent Research and Future Prospect)

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15 pages, 6456 KiB

Open AccessArticle

Orthogonal Design and Microstructure Mechanism Analysis of Novel Bentonite Polymer Slurry in Pipe Jacking

by Jimin Liu, Xiangzhi Wang, Hua Cheng and Haixu Fan

Polymers 2023, 15(6), 1461; https://doi.org/10.3390/polym15061461 - 15 Mar 2023

Cited by 1 | Viewed by 1243

Abstract

The selection of an appropriate slurry ingredient and its percentage ratio is a vital and necessary task for engineers in slurry pipe jacking operations. However, traditional bentonite grouting materials are difficult to degrade because of their single and non-biodegradable composition. Nowadays crosslinked polymers have been widely considered due to their excellent performance and application in engineering practices, which enlighten novel polymer slurry in pipe jacking. This study innovatively proposed using boric acid crosslinked polymers added into polyacrylamide bentonite slurry, which not only solves the shortcomings of traditional grouting materials but also meets the general working performance requirements. The new slurry’s funnel viscosity, filter loss, water dissociation ratio and dynamic shear were tested according to an orthogonal experiment. Single factor range analysis was conducted to identify the optimal mix proportion based on an orthogonal design, and the formation behavior of mineral crystals and microstructure characteristics were evaluated by X-ray diffraction and scanning electron microscopy respectively. According to the results, guar gum and borax form a dense boric acid crosslinked polymer through cross-linking reaction. The internal structure grew tighter and more continuous as the crosslinked polymer concentration grew. It improved the anti-permeability plugging action and viscosity of slurries by 36.1~94.3%. The optimal proportions of sodium bentonite, guar gum, polyacrylamide, borax, and water were 10%, 0.2%, 0.25%, 0.1%, and 89.45% respectively. All these works indicated that the improvement of slurry composition by using boric acid crosslinked polymers was feasible. Full article

(This article belongs to the Special Issue Geopolymers: Recent Research and Future Prospect)

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Review

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25 pages, 4574 KiB

Open AccessReview

Geopolymer Materials for Bone Tissue Applications: Recent Advances and Future Perspectives

by Laura Ricciotti, Antonio Apicella, Valeria Perrotta and Raffaella Aversa

Polymers 2023, 15(5), 1087; https://doi.org/10.3390/polym15051087 - 22 Feb 2023

Cited by 13 | Viewed by 3999

Abstract

With progress in the bone tissue engineering (BTE) field, there is an important need to develop innovative biomaterials to improve the bone healing process using reproducible, affordable, and low-environmental-impact alternative synthetic strategies. This review thoroughly examines geopolymers’ state-of-the-art and current applications and their future perspectives for bone tissue applications. This paper aims to analyse the potential of geopolymer materials in biomedical applications by reviewing the recent literature. Moreover, the characteristics of materials traditionally used as bioscaffolds are also compared, critically analysing the strengths and weaknesses of their use. The concerns that prevented the widespread use of alkali-activated materials as biomaterials (such as their toxicity and limited osteoconductivity) and the potentialities of geopolymers as ceramic biomaterials have also been considered. In particular, the possibility of targeting their mechanical properties and morphologies through their chemical compositions to meet specific and relevant requirements, such as biocompatibility and controlled porosity, is described. A statistical analysis of the published scientific literature is presented. Data on “geopolymers for biomedical applications” were extracted from the Scopus database. This paper focuses on possible strategies necessary to overcome the barriers that have limited their application in biomedicine. Specifically, innovative hybrid geopolymer-based formulations (alkali-activated mixtures for additive manufacturing) and their composites that optimise the porous morphology of bioscaffolds while minimising their toxicity for BTE are discussed. Full article

(This article belongs to the Special Issue Geopolymers: Recent Research and Future Prospect)

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