Special Issue "Alkali Activated Materials: Advances, Innovations, Future Trends"

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Processing and Metallurgy".

Deadline for manuscript submissions: 31 August 2020.

Special Issue Editors

Prof. Dr. Konstantinos Komnitsas
E-Mail Website1 Website2
Guest Editor
Department of Mineral Resources Engineering, Technical University of Crete (TUC), 73100 Chania, Hellas, Greece
Interests: waste valorization; hydrometallurgy; life cycle analysis; risk assessment; environmental monitoring and modelling; soil and groundwater protection and rehabilitation
Special Issues and Collections in MDPI journals
Dr. Georgios Bartzas
E-Mail Website1 Website2
Guest Editor
School of Mining and Metallurgical Engineering, National Technical University of Athens, 15780 Athens, Greece
Interests: risk assessment; environmental monitoring and modelling, soil and groundwater protection and rehabilitation; life cycle analysis, waste valorization; hydrometallurgy
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Alkali activated materials (AAMs) are binders, sometimes named geopolymers, that are produced through the reaction of an alkali source and aluminosilicates. The most commonly used alkali sources are sodium or potassium hydroxides and/or silicates, while aluminosilicates may include suitable raw materials and wastes. AAMs can be commercialized in various industrial sectors, and especially in the construction sector. When produced from industrial wastes, including, for example, various metallurgical slags, coal fly ash, construction and demolition wastes, as well others, the environmental footprint of the construction sector may be substantially reduced. This Special Issue welcomes papers highlighting the advances, innovations, and future trends pertinent to the alkali activation of wastes for the production of AAMs. Emphasis is also given on the production of eco-efficient cements, as well as on new processing routes, quality control, life-cycle analysis, environmental footprint, large scale applications, barriers and incentives, development and optimization of mix designs, analysis of durability characteristics, use of activators with lower environmental impact, validation and standardization of testing methods, and on all issues that contribute to the sustainability of the construction sector.

Prof. Kostas A. Komnitsas
Dr. Georgios Bartzas
Guest Editors

Manuscript Submission Information

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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. Minerals is an international peer-reviewed open access monthly 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 1600 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

  • alkali activation
  • fly ash
  • slag
  • construction and demolition wastes
  • metakaolin
  • eco-efficient cement
  • life cycle analysis
  • environmental footprint

Published Papers (5 papers)

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Research

Open AccessArticle
Effect of Ordinary Portland Cement and Water Glass on the Properties of Alkali Activated Fly Ash Concrete
Minerals 2020, 10(1), 40; https://doi.org/10.3390/min10010040 - 31 Dec 2019
Abstract
This research presents the influence of ordinary Portland cement (OPC) and/or water glass addition on fly ash alkali-activated mortar and concrete. The results show that fly ash (FA) concrete activated with a NaOH solution and water glass mixture had better resistance to freeze [...] Read more.
This research presents the influence of ordinary Portland cement (OPC) and/or water glass addition on fly ash alkali-activated mortar and concrete. The results show that fly ash (FA) concrete activated with a NaOH solution and water glass mixture had better resistance to freeze and thaw, carbonation, alkali-silica reaction (ASR) and developed higher compressive strength and static elastic modulus compared with the FA concrete activated only with an NaOH solution. The addition of OPC contributes to the development of a denser microstructure of alkali activated concrete (AAC) samples. In the presence of water glass and OPC, the compressive strength (52.60 MPa) of the samples increased more than two times as compared with the reference sample (21.36 MPa) without OPC and water glass. The combination of OPC and water glass showed the increased strength and enhanced durability of AAC. The samples were more resistant to freeze and thaw, ASR, and carbonation. Full article
(This article belongs to the Special Issue Alkali Activated Materials: Advances, Innovations, Future Trends)
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Open AccessArticle
Effect of the Sodium Silicate Modulus and Slag Content on Fresh and Hardened Properties of Alkali-Activated Fly Ash/Slag
Minerals 2020, 10(1), 15; https://doi.org/10.3390/min10010015 - 23 Dec 2019
Abstract
This paper presents the results of an experimental study performed to investigate the effect of activator modulus (SiO2/Na2O) and slag addition on the fresh and hardened properties of alkali-activated fly ash/slag (AAFS) pastes. Four activator moduli (SiO2/Na [...] Read more.
This paper presents the results of an experimental study performed to investigate the effect of activator modulus (SiO2/Na2O) and slag addition on the fresh and hardened properties of alkali-activated fly ash/slag (AAFS) pastes. Four activator moduli (SiO2/Na2O), i.e., 0.0, 1.0, 1.5, and 2.0, and five slag-to-binder ratios, i.e., 0, 0.3, 0.5, 0.7, 1.0, were used to prepare AAFS mixtures. The setting time, flowability, heat evolution, compressive strength, microstructure, and reaction products of AAFS pastes were studied. The results showed that the activator modulus and slag content had a combined effect on the setting behavior and workability of AAFS mixtures. Both the activator modulus and slag content affected the types of reaction products formed in AAFS. The coexistence of N–A–S–H gel and C–A–S–H gel was identified in AAFS activated with high pH but low SiO2 content (low modulus). C–A–S–H gel had a higher space-filling ability than N–A–S–H gel. Thus, AAFS with higher slag content had a finer pore structure and higher heat release (degree of reaction), corresponding to a higher compressive strength. The dissolution of slag was more pronounced when NaOH (modulus of 0.0) was applied as the activator. The use of Na2SiO3 as activator significantly refined the pores in AAFS by incorporating soluble Si in the activator, while further increasing the modulus from 1.5 to 2.0 prohibited the reaction process of AAFS, resulting in a lower heat release, coarser pore structure, and reduced compressive strength. Therefore, in view of the strength and microstructure, the optimum modulus is 1.5. Full article
(This article belongs to the Special Issue Alkali Activated Materials: Advances, Innovations, Future Trends)
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Open AccessArticle
Acid and Thermal Treatment of Alkali-Activated Zeolite Foams
Minerals 2019, 9(12), 719; https://doi.org/10.3390/min9120719 - 20 Nov 2019
Abstract
The foamed alkali-activated zeolite materials have been studied primarily in terms of mechanical and structural properties as potential substitutes for concrete and other building materials. However, they also have interesting textural and acid properties that make them much more useful, especially in the [...] Read more.
The foamed alkali-activated zeolite materials have been studied primarily in terms of mechanical and structural properties as potential substitutes for concrete and other building materials. However, they also have interesting textural and acid properties that make them much more useful, especially in the chemical industry. The aim of the study is to map in detail the influence of post-synthesis modifications of alkali-activated natural zeolite foams on their chemical, mechanical, and textural properties for possible use in catalytic and adsorption applications. Alkali-activated natural zeolite foam pellets were prepared by activation with mixed potassium hydroxide and sodium silicate activator and foamed using H2O2 solution. The foam pellets were post-synthetic modified by leaching with mineral and organic acids and calcination. The properties of the modified materials were characterised on the basis of XRF, XRD, N2 physisorption, DRIFT, SEM, NH3-TPD analyses, and the strength measurements. Our data showed that the basic clinoptilolite structure remains unchanged in the material which is stable up to 600 °C after acid leaching. In two-step leaching, the specific surface area increases to 350 m2/g and the leaching process allows the acid properties of the materials to be varied. Full article
(This article belongs to the Special Issue Alkali Activated Materials: Advances, Innovations, Future Trends)
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Open AccessArticle
Grinding Kinetics of Slag and Effect of Final Particle Size on the Compressive Strength of Alkali Activated Materials
Minerals 2019, 9(11), 714; https://doi.org/10.3390/min9110714 - 19 Nov 2019
Cited by 1
Abstract
This study aims to model grinding of a Polish ferronickel slag and evaluate the particle size distributions (PSDs) of the products obtained after different grinding times. Then, selected products were alkali activated in order to investigate the effect of particle size on the [...] Read more.
This study aims to model grinding of a Polish ferronickel slag and evaluate the particle size distributions (PSDs) of the products obtained after different grinding times. Then, selected products were alkali activated in order to investigate the effect of particle size on the compressive strength of the produced alkali activated materials (AAMs). Other parameters affecting alkali activation, i.e., temperature, curing, and ageing time were also examined. Among the different mathematical models used to simulate the particle size distribution, Rosin–Rammler (RR) was found to be the most suitable. When piecewise regression analysis was applied to experimental data it was found that the particle size distribution of the slag products exhibits multifractal character. In addition, grinding of slag exhibits non-first-order behavior and the reduction rate of each size is time dependent. The grinding rate and consequently the grinding efficiency increases when the particle size increases, but drops sharply near zero after prolonged grinding periods. Regarding alkali activation, it is deduced that among the parameters studied, particle size (and the respective specific surface area) of the raw slag product and curing temperature have the most noticeable impact on the compressive strength of the produced AAMs. Full article
(This article belongs to the Special Issue Alkali Activated Materials: Advances, Innovations, Future Trends)
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Open AccessArticle
Low-Carbon Binder for Cemented Paste Backfill: Flowability, Strength and Leaching Characteristics
Minerals 2019, 9(11), 707; https://doi.org/10.3390/min9110707 - 15 Nov 2019
Abstract
Blast furnace slag was used as the main raw material to prepare the alkali activated slag (AAS), a low-carbon binder, for cemented paste backfill (CPB). The optimum parameters for preparing the AAS binders using an orthogonal experiment were obtained. Under the optimum conditions [...] Read more.
Blast furnace slag was used as the main raw material to prepare the alkali activated slag (AAS), a low-carbon binder, for cemented paste backfill (CPB). The optimum parameters for preparing the AAS binders using an orthogonal experiment were obtained. Under the optimum conditions (NaOH content was 3 wt. %, Ordinary Portland cement (OPC) content was 7 wt. %, and gypsum dosage was 4 wt. %), the 28 days compressive strength of the binder was 29.55 MPa. The flow ability of the fresh CPB slurry decreased with solid content due to the increased yield stress, while the flow ability increased when rising the binder dosage. A predictive model for the compressive strength of CPB samples was reached through multivariate analysis and the R2 values were higher than 0.9. Sensitivity analysis showed that the solid content is the most important parameter which influences on the development of the CPB strength with a correlation coefficient of 0.826. From the Toxicity Characteristic Leaching Procedure (TCLP) tests, the leaching concentrations of Pb and Cd were below the threshold. As a result, the AAS has potential application as an alternative binder and cemented paste backfill. Full article
(This article belongs to the Special Issue Alkali Activated Materials: Advances, Innovations, Future Trends)
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