Editorial

5 pages, 207 KiB

Open AccessEditorial

Editorial for Special Issue: Alkali Activated Materials: Advances, Innovations, Future Trends

by Kostas A. Komnitsas and Georgios Bartzas

Minerals 2021, 11(1), 75; https://doi.org/10.3390/min11010075 - 14 Jan 2021

Cited by 3 | Viewed by 2460

Alkali activated materials (AAMs), also named geopolymers or inorganic polymers, are materials that are produced when alkaline solutions react with precursors containing aluminosilicate phases [...] Full article

(This article belongs to the Special Issue Alkali Activated Materials: Advances, Innovations, Future Trends)

Research

Jump to: Editorial, Review

16 pages, 4430 KiB

Open AccessArticle

Marble Waste Valorization through Alkali Activation

by Konstantinos Komnitsas, Athanasia Soultana and Georgios Bartzas

Minerals 2021, 11(1), 46; https://doi.org/10.3390/min11010046 - 02 Jan 2021

Cited by 14 | Viewed by 2663

Abstract

In the present study, the valorization potential of marble waste in the presence of metakaolin via alkali activation was explored. The activating solution used consisted of NaOH and sodium silicate solutions. The effects of marble waste to metakaolin ratio, particle size of raw [...] Read more.

In the present study, the valorization potential of marble waste in the presence of metakaolin via alkali activation was explored. The activating solution used consisted of NaOH and sodium silicate solutions. The effects of marble waste to metakaolin ratio, particle size of raw materials, curing temperature, and Na₂O/SiO₂ and H₂O/Na₂O molar ratios present in the activating solution on the main properties and the morphology of the produced alkali-activated materials (AAMs) was evaluated. The durability and structural integrity of the AAMs after firing at temperatures between 200 and 600 °C, immersion in deionized water and 1 mol/L NaCl solution for different time periods and subjection to freeze–thaw cycles were also investigated. Characterization techniques including Fourier transform infrared spectroscopy, X-ray diffraction, mercury intrusion porosimetry and scanning electron microscopy were used in order to study the structure of the produced AAMs. Τhe highest compressive strength (~36 MPa) was achieved by the AAMs prepared with marble waste to metakaolin mass ratio of 0.3 after curing at 40 °C. The results indicated that the utilization of marble waste in the presence of metakaolin enables the production of AAMs with good physical (porosity, density and water absorption) and mechanical properties, thus contributing to the valorization of this waste type and the reduction of the environmental footprint of the marble industry. Full article

(This article belongs to the Special Issue Alkali Activated Materials: Advances, Innovations, Future Trends)

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17 pages, 6796 KiB

Open AccessArticle

Low-Calcium, Porous, Alkali-Activated Materials as Novel pH Stabilizers for Water Media

by Laura Vitola, Diana Bajare, Angel Palomo and Ana Fernandez-Jimenez

Minerals 2020, 10(11), 935; https://doi.org/10.3390/min10110935 - 22 Oct 2020

Cited by 8 | Viewed by 1893

Abstract

Due to the increase of water consumption, water treatment systems become more actual and innovative materials for water treatment are welcomed. Traditionally, alkalizing agents, such as lime or caustic soda, have been employed to increase the pH levels, which induce chemical clarification of [...] Read more.

Due to the increase of water consumption, water treatment systems become more actual and innovative materials for water treatment are welcomed. Traditionally, alkalizing agents, such as lime or caustic soda, have been employed to increase the pH levels, which induce chemical clarification of wastewater. Some innovative ideas of using low-calcium, alkali-activated materials (AAM) for this purpose have been considered previously. In this study, the low-calcium, porous, alkali-activated material (pAAM) was characterized to understand the impact of the aluminum silicate source and heat treatment on basic properties for material that might be used in water treatment systems as a softener by stabilizing the pH. The studied porous alkali-activated materials may ensure stable and long-lasting (30 days) pH (pH 10.3–11.6) in water media depending on the composition and amount of activation solution used for AAM preparation. Heat treatment does not have an impact on the mineralogical composition and structural properties of the pAAM, but it does change the leaching ability of alkalis from the material structure. Full article

(This article belongs to the Special Issue Alkali Activated Materials: Advances, Innovations, Future Trends)

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21 pages, 7789 KiB

Open AccessArticle

Synthesis of Fly Ash-Based Geopolymers: Effect of Calcite Addition and Mechanical Activation

by Alexander M. Kalinkin, Basya I. Gurevich, Mikhail S. Myshenkov, Mikhail V. Chislov, Elena V. Kalinkina, Irina A. Zvereva, Zara Cherkezova-Zheleva, Daniela Paneva and Vilma Petkova

Minerals 2020, 10(9), 827; https://doi.org/10.3390/min10090827 - 20 Sep 2020

Cited by 27 | Viewed by 3196

Abstract

Blends of fly ash and natural calcite, mechanically activated for 0–400 s in a planetary mill, were used to synthesize geopolymers at ambient temperature. The calcite content in the blends was 0–10 wt.%. Sodium hydroxide solution was used as an alkaline agent. Mechanical [...] Read more.

Blends of fly ash and natural calcite, mechanically activated for 0–400 s in a planetary mill, were used to synthesize geopolymers at ambient temperature. The calcite content in the blends was 0–10 wt.%. Sodium hydroxide solution was used as an alkaline agent. Mechanical activation of the raw material considerably enhanced its reactivity with respect to the alkaline agent, as was observed using Fourier-transform infrared spectroscopy, isothermal conduction calorimetry, thermogravimetry coupled with mass spectrometry analysis of the evolved gas, and SEM/EDS. The addition of calcite to the fly ash improved the compressive strength of the geopolymers, especially during the early age of curing. For 7 d aged geopolymers based on the 90% fly ash + 10% calcite blend, the strength was 8.0-, 3.5- and 2.9-fold higher than that for the geopolymers based on the unblended fly ash for 30 s, 180 s and 400 s mechanical activation time, respectively. Using Mössbauer spectroscopy, it was revealed that iron present in the fly ash did not play a significant part in the geopolymerization process. The dominant reaction product was sodium containing aluminosilicate hydrogel (N-A-S-H gel). Calcite was found to transform, to a small extent, to vaterite and Ca(OH)₂ in the course of the geopolymerization. Full article

(This article belongs to the Special Issue Alkali Activated Materials: Advances, Innovations, Future Trends)

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17 pages, 3518 KiB

Open AccessArticle

Microstructure and Pb²⁺ Adsorption Properties of Blast Furnace Slag and Fly Ash based Geopolymers

by T. J. Medina, S. P. Arredondo, R. Corral, A. Jacobo, R. A. Zárraga, C. A. Rosas, F. G. Cabrera and J. M. Bernal

Minerals 2020, 10(9), 808; https://doi.org/10.3390/min10090808 - 13 Sep 2020

Cited by 19 | Viewed by 2847

Abstract

In this study, a blast furnace slag (BFS) and fly ash (FA) based adsorbent geopolymer to be used for removing Pb²⁺ from aqueous solutions were synthesized using the hydrothermal method at 60 °C for 24 h, and then cured at 25 °C [...] Read more.

In this study, a blast furnace slag (BFS) and fly ash (FA) based adsorbent geopolymer to be used for removing Pb²⁺ from aqueous solutions were synthesized using the hydrothermal method at 60 °C for 24 h, and then cured at 25 °C for another six days. The alkali activator applied in this work was a combination of sodium hydroxide and sodium silicate solutions at a mass ratio of 2. The geopolymer slurry was adjusted to a Si/Al molar ratio of 3. A BFS-based geopolymer (GS) having a specific area of 23.56 m²/g and pore size and volume of 7.8 nm and 73 cm³/kg, respectively, surpassed the raw material surface by approximately 13-fold. An FA-based geopolymer (GA) having a specific area of 35.97 m²/g and a size and porous volume of 9 nm and 124 nm, respectively, surpassed the raw material surface by approximately 23-fold. In addition, GS and GA showed a cation exchange capacity (CEC) of 241.30 and 286.96 Meq/100 g, respectively. X-ray diffraction (XRD) determined sample crystallinity and it was proven by scanning electron microscopy (SEM), showing that both geopolymers were constituted of unreacted particles surrounded by amorphous and semi-amorphous products. Through Fourier transform infrared spectroscopy (FTIR), a band that was assigned to the asymmetric stretching vibration of Si-O-M (M = Na⁺ and/or Ca²⁺) non-bridging oxygen type was observed, which suggested that Na and Ca could serve as exchangeable ions in the ionic exchange process. Adsorption test data indicated that good adsorption was obtained when a neutral pH was used at room temperature, and the adsorption isotherm showed that GA had more adsorption sites than GS, which meant greater maximum adsorption capacity. Full article

(This article belongs to the Special Issue Alkali Activated Materials: Advances, Innovations, Future Trends)

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16 pages, 3155 KiB

Open AccessArticle

Rheology of Alkali-Activated Mortars: Influence of Particle Size and Nature of Aggregates

by Sara Gismera, María del Mar Alonso, Marta Palacios and Francisca Puertas

Minerals 2020, 10(8), 726; https://doi.org/10.3390/min10080726 - 18 Aug 2020

Cited by 8 | Viewed by 2266

Abstract

The effect of two precursors (slag and fly ash), different particle size distribution, and three types of aggregate (siliceous sand, limestone, and recycled concrete) on alkali-activated material (AAM) mortar rheology were studied and compared to their effect on an ordinary Portland Cement (OPC) [...] Read more.

The effect of two precursors (slag and fly ash), different particle size distribution, and three types of aggregate (siliceous sand, limestone, and recycled concrete) on alkali-activated material (AAM) mortar rheology were studied and compared to their effect on an ordinary Portland Cement (OPC) mortar reference. Stress growth and flow curve tests were conducted to determine plastic viscosity and static and dynamic yield stress of the AAM and OPC mortars. In both OPC and AAM mortars, a reduction of the aggregate size induces a rise of the liquid demand to preserve the plastic consistency of the mortar. In general terms, an increase of the particle size of the siliceous aggregates leads to a decrease of the measured rheological parameters. The AAM mortars require higher liquid/solid ratios than OPC mortars to attain plastic consistency. AAM mortars proved to be more sensitive than OPC mortars to changes in aggregate nature. The partial replacement of the siliceous aggregates with up to 20% of recycled concrete aggregates induced no change in mixing liquid uptake, in either AAM or OPC mortars. All the AAM and OPC mortars studied fitted to the Bingham model. Full article

(This article belongs to the Special Issue Alkali Activated Materials: Advances, Innovations, Future Trends)

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16 pages, 5121 KiB

Open AccessArticle

Valorization of Brick and Glass CDWs for the Development of Geopolymers Containing More Than 80% of Wastes

by Dimitris Kioupis, Aggeliki Skaropoulou, Sotirios Tsivilis and Glikeria Kakali

Minerals 2020, 10(8), 672; https://doi.org/10.3390/min10080672 - 29 Jul 2020

Cited by 28 | Viewed by 3161

Abstract

One of the areas of priority in a circular economy, regarding waste management, regards the valorization of construction and demolition wastes (CDW). This study suggests the synthesis of geopolymeric binders based almost entirely on construction and demolition wastes. Ceramic waste was used as [...] Read more.

One of the areas of priority in a circular economy, regarding waste management, regards the valorization of construction and demolition wastes (CDW). This study suggests the synthesis of geopolymeric binders based almost entirely on construction and demolition wastes. Ceramic waste was used as the aluminosilicate precursor of the geopolymer synthesis, while glass waste was applied in the preparation of the activation solution. A fractional experimental design defined the optimum synthesis parameters, based on compressive strength values. The final products were characterized by means of X-Ray Diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The glass waste was appropriately processed in order to prepare the activation solution for the geopolymerization of brick waste. In this work, CDW-based geopolymers were produced with a compressive strength in the range 10–44 MPa. The developed products contained 80–90 wt.% CDWs, depending on the method of activator preparation. Full article

(This article belongs to the Special Issue Alkali Activated Materials: Advances, Innovations, Future Trends)

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13 pages, 3871 KiB

Open AccessArticle

Modified Alkali Activated Zeolite Foams with Improved Textural and Mechanical Properties

by Kateřina Hrachovcová, Zdeněk Tišler, Eliška Svobodová and Jan Šafář

Minerals 2020, 10(5), 483; https://doi.org/10.3390/min10050483 - 25 May 2020

Cited by 14 | Viewed by 2773

Abstract

Natural zeolites are crystalline hydrated alkali metal and alkaline earth metal aluminosilicates with unique ion-exchange and sorption properties. The exceptional structure of pores gives natural zeolites several application possibilities, especially for water treatment and construction. For a wider use of natural zeolites, such [...] Read more.

Natural zeolites are crystalline hydrated alkali metal and alkaline earth metal aluminosilicates with unique ion-exchange and sorption properties. The exceptional structure of pores gives natural zeolites several application possibilities, especially for water treatment and construction. For a wider use of natural zeolites, such as catalysis, properties—especially chemical, textural, and mechanical—need to be modified. In this study, the basic natural zeolite foam was synthesized by alkali activation of natural zeolite with an activator (KOH + Na₂SiO₃) and foamed by hydrogen peroxide solution. Other foams were prepared by a partial replacement of the natural zeolite with CaO, MgO, and metakaolin (MK) and alkali activated and foamed in the same manner as the basic natural zeolite foam. Other properties of the foams were modified by acid leaching. The aim of the study was to compare the basic alkali activated zeolite foam with the CaO, MgO, and MK modified zeolite foams and determine the effect of the CaO, MgO, and MK modification and the subsequent leaching of the alkali activated zeolite foams on the textural, mechanical, and chemical properties. Properties of alkali activated zeolite foams were determined by Hg porosimetry, N₂ physisorption, NH₃-TPD, XRF, XRD, and strength analyses. From the data, it is apparent that all modified samples have an increase of pore volume in the mesoporous region and the partial replacement by MgO or CaO significantly increased surface area up to 288.2 m²/g while increasing the strength several times. The obtained data showed an improvement in properties and extension of the potential applicability of modified zeolite foams in the chemical industry, especially for catalytic and sorption applications. Full article

(This article belongs to the Special Issue Alkali Activated Materials: Advances, Innovations, Future Trends)

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14 pages, 2246 KiB

Open AccessEditor’s ChoiceArticle

Rheological Properties of Cemented Paste Backfill with Alkali-Activated Slag

by Yunpeng Kou, Haiqiang Jiang, Lei Ren, Erol Yilmaz and Yuanhui Li

Minerals 2020, 10(3), 288; https://doi.org/10.3390/min10030288 - 22 Mar 2020

Cited by 72 | Viewed by 3938

Abstract

This study investigates the time-dependent rheological behavior of cemented paste backfill (CPB) that contains alkali-activated slag (AAS) as a binder. Rheological measurements with the controlled shear strain method have been conducted on various AAS-CPB samples with different binder contents, silicate modulus (Ms: SiO [...] Read more.

This study investigates the time-dependent rheological behavior of cemented paste backfill (CPB) that contains alkali-activated slag (AAS) as a binder. Rheological measurements with the controlled shear strain method have been conducted on various AAS-CPB samples with different binder contents, silicate modulus (Ms: SiO₂/Na₂O molar ratio), fineness of slag and curing temperatures. The Bingham model afforded a good fit to all of the CPB mixtures. The results show that AAS-CPB samples with high binder content demonstrate a more rapid rate of gain in yield stress and plastic viscosity. AAS-CPB also shows better rheological behavior than CPB samples made up of ordinary Portland cement (OPC) at identical binder contents. It is found that increasing Ms yields lower yield stress and plastic viscosity and the rate of gain in these parameters. Increases in the fineness of slag has an adverse effect on rheological behavior of AAS-CPB. The rheological behavior of both OPC- and AAS-CPB samples is also strongly enhanced at higher temperatures. AAS-CPB samples are found to be more sensitive to the variation in curing temperatures than OPC-CPB samples with respect to the rate of gain in yield stress and plastic viscosity. As a result, the findings of this study will contribute to well understand the flow and transport features of fresh CPB mixtures under various conditions and their changes with time. Full article

(This article belongs to the Special Issue Alkali Activated Materials: Advances, Innovations, Future Trends)

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10 pages, 2759 KiB

Open AccessArticle

Effect of Ordinary Portland Cement and Water Glass on the Properties of Alkali Activated Fly Ash Concrete

by Vytautas Bocullo, Danutė Vaičiukynienė, Ramūnas Gečys and Mindaugas Daukšys

Minerals 2020, 10(1), 40; https://doi.org/10.3390/min10010040 - 31 Dec 2019

Cited by 4 | Viewed by 3535

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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17 pages, 6344 KiB

Open AccessArticle

Effect of the Sodium Silicate Modulus and Slag Content on Fresh and Hardened Properties of Alkali-Activated Fly Ash/Slag

by Xiaowei Ouyang, Yuwei Ma, Ziyang Liu, Jianjun Liang and Guang Ye

Minerals 2020, 10(1), 15; https://doi.org/10.3390/min10010015 - 23 Dec 2019

Cited by 48 | Viewed by 5554

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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19 pages, 18842 KiB

Open AccessEditor’s ChoiceArticle

Acid and Thermal Treatment of Alkali-Activated Zeolite Foams

by Zdeněk Tišler, Kateřina Hrachovcová, Eliška Svobodová, Jan Šafář and Lenka Pelíšková

Minerals 2019, 9(12), 719; https://doi.org/10.3390/min9120719 - 20 Nov 2019

Cited by 14 | Viewed by 5195

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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21 pages, 4918 KiB

Open AccessEditor’s ChoiceArticle

Grinding Kinetics of Slag and Effect of Final Particle Size on the Compressive Strength of Alkali Activated Materials

by Evangelos Petrakis, Vasiliki Karmali, Georgios Bartzas and Konstantinos Komnitsas

Minerals 2019, 9(11), 714; https://doi.org/10.3390/min9110714 - 19 Nov 2019

Cited by 33 | Viewed by 4233

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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15 pages, 829 KiB

Open AccessArticle

Low-Carbon Binder for Cemented Paste Backfill: Flowability, Strength and Leaching Characteristics

by Jingping Qiu, Yingliang Zhao, Hui Long, Zhenbang Guo, Jun Xing and Xiaogang Sun

Minerals 2019, 9(11), 707; https://doi.org/10.3390/min9110707 - 15 Nov 2019

Cited by 21 | Viewed by 3035

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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Review

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32 pages, 4906 KiB

Open AccessReview

Self-Sensing Alkali-Activated Materials: A Review

by Christos Vlachakis, Marcus Perry and Lorena Biondi

Minerals 2020, 10(10), 885; https://doi.org/10.3390/min10100885 - 06 Oct 2020

Cited by 22 | Viewed by 3915

Abstract

Alkali-activated materials are an emerging technology that can serve as an alternative solution to ordinary Portland cement. Due to their alkaline nature, these materials are inherently more electrically conductive than ordinary Portland cement, and have therefore seen numerous applications as sensors and self-sensing [...] Read more.

Alkali-activated materials are an emerging technology that can serve as an alternative solution to ordinary Portland cement. Due to their alkaline nature, these materials are inherently more electrically conductive than ordinary Portland cement, and have therefore seen numerous applications as sensors and self-sensing materials. This review outlines the current state-of-the-art in strain, temperature and moisture sensors that have been developed using alkali activated materials. Sensor fabrication methods, electrical conductivity mechanisms, and comparisons with self-sensing ordinary Portland cements are all outlined to highlight best practice and propose future directions for research. Full article

(This article belongs to the Special Issue Alkali Activated Materials: Advances, Innovations, Future Trends)

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