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26 pages, 10141 KiB

Open AccessArticle

Study of Novel Geopolymer Concrete Prepared with Slate Stone Cutting Sludge, Chamotte, Steel Slag and Activated with Olive Stone Bottom Ash

by Raul Carrillo Beltran, Elena Picazo Camilo, Griselda Perea Toledo and Francisco Antonio Corpas Iglesias

Materials 2025, 18(9), 1974; https://doi.org/10.3390/ma18091974 - 26 Apr 2025

Viewed by 271

Abstract

The expansion of the construction sector has contributed to the depletion of raw materials and an increased demand for resources; therefore, sustainable approaches are required to satisfy the construction demand. The present study explores the development of geopolymers by utilizing industrial by-products from [...] Read more.

The expansion of the construction sector has contributed to the depletion of raw materials and an increased demand for resources; therefore, sustainable approaches are required to satisfy the construction demand. The present study explores the development of geopolymers by utilizing industrial by-products from mining, ceramics, olive oil production, and steel manufacturing. Specifically, slate stone cutting sludge (SSCS) and chamotte (CH) are used as aluminosilicate precursors, with olive biomass bottom ash (OSBA) acting as an alkaline activator, along with sodium silicate, and steel granulated slag (SGS) incorporated as an aggregate. Novel geopolymers were prepared with consistent proportions of SSCS and OSBA while varying the CH content from 10 to 2 wt.%. The SGS proportion was adjusted from 35 to 50 wt.%, and different Na₂SiO₃/OSBA ratios (0.35, 0.31, 0.19, and 0.08) were examined. To identify the optimal mix, a series of physical and mechanical tests was conducted, complemented by FTIR and SEM analysis to evaluate the chemical and microstructural changes. The best-performing formulation achieved a compressive strength of 42.8 MPa after 28 days of curing. FTIR analysis identified quartz and carbonate phases, suggesting that quartz did not fully dissolve and that carbonates formed during the heating process. SEM examination of the optimal mixture indicated that the incorporation of SGS (up to 45 wt.%) facilitated the creation of a compact, low-porosity structure. EDX results revealed the presence of Ca-, Na-, Si-, Al-, and K-enriched phases, supporting the formation of (N, C)-A-S-H gel networks. These results demonstrate the potential of utilizing SSCS, CH, OSBA, and SGS to create geopolymer concretes, showcasing the viability of using industrial by-products as eco-friendly substitutes for traditional construction materials. Full article

(This article belongs to the Special Issue Advances in Function Geopolymer Materials)

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35 pages, 22378 KiB

Open AccessArticle

Study of Properties of Novel Geopolymers Prepared with Slate Stone Cutting Sludge and Activated with Olive Stone Bottom Ash

by Elena Picazo Camilo, Juan José Valenzuela Expósito, Raúl Carrillo Beltrán, Griselda Elisabeth Perea Toledo and Francisco Antonio Corpas Iglesias

Materials 2025, 18(8), 1774; https://doi.org/10.3390/ma18081774 - 13 Apr 2025

Viewed by 420

Abstract

The sustainable development of building materials is based on reusing by-products to reduce environmental impact and promote alternatives to traditional materials. In this study, geopolymers were developed from by-products of the mining, ceramic, and thermal industries: slate stone cutting sludge (SSCS) and chamotte [...] Read more.

The sustainable development of building materials is based on reusing by-products to reduce environmental impact and promote alternatives to traditional materials. In this study, geopolymers were developed from by-products of the mining, ceramic, and thermal industries: slate stone cutting sludge (SSCS) and chamotte (CH) as aluminosilicate sources, and olive stone bottom ash (OSBA) as an alkaline activator, combined with sodium silicate (Na₂SiO₃). Eight geopolymer families were prepared with constant amounts of SSCS and CH and varying proportions of OSBA/Na₂SiO₃ (0.88–1.31). The evaluation phase included physical, chemical, mechanical, and microstructural tests. The results showed that the optimum geopolymer formulation (GP E) contained 25% SSCS, 15% CH, and 19% OSBA with a Na₂SiO₃/OSBA ratio of 1.0, achieving a compressive strength of 24.12 MPa after 28 days of curing. GP E also showed the lowest porosity (19.54%), minimal water absorption (6.86%), and favorable thermal conductivity (0.688 W/mK). Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) confirmed the formation of dense and homogeneous matrices. These results demonstrate the feasibility of manufacturing geopolymers using SSCS, CH, and OSBA as substitutes for traditional binders, promoting sustainable practices, reusing industrial by-products, and reducing carbon emissions in construction. Full article

(This article belongs to the Special Issue Advances in Function Geopolymer Materials)

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15 pages, 5050 KiB

Open AccessArticle

A Comparison of the Resistance- and Capacitance-Based Sensing of Geopolymer and Cement Composites with Graphite Filler Under Compression

by Pavel Rovnaník, Ivo Kusák, Pavel Schmid and Patrik Bayer

Materials 2025, 18(4), 750; https://doi.org/10.3390/ma18040750 - 8 Feb 2025

Viewed by 550

Abstract

Aluminosilicate binders, such as Portland cement or geopolymers, are generally considered electrical insulators. In order to decrease their electrical resistance, electrically conductive fillers are added. This brings new application possibilities, such as the self-sensing and self-monitoring of smart structures. In this study, three [...] Read more.

Aluminosilicate binders, such as Portland cement or geopolymers, are generally considered electrical insulators. In order to decrease their electrical resistance, electrically conductive fillers are added. This brings new application possibilities, such as the self-sensing and self-monitoring of smart structures. In this study, three different aluminosilicate composites with the same amount of fine graphite filler (6% with respect to the basic aluminosilicate raw material) were tested for resistance- and capacitance-based self-sensing properties. Portland cement and two geopolymer binders were used as the basic matrices for the conductive composites. The composites were tested for self-sensing properties in repeated compression in the elastic area, static mechanical properties, and microstructure using scanning electron microscopy and mercury intrusion porosimetry. The results showed that alkali-activated materials are less stiff than Portland cement composite; however, they provide better self-sensing properties, regardless of the measured electrical parameters. The highest capacitance-based gauge factor 74.5 was achieved with the blended slag/fly ash geopolymer composite, whereas the cement composite showed very poor sensitivity, with a gauge factor of 10.2. The study showed a new possibility of self-sensing based on the measurement of capacitance, which is suitable for geopolymers and alkali-activated composites; however, in the case of cement composites, it is very limited. Full article

(This article belongs to the Special Issue Advances in Function Geopolymer Materials)

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30 pages, 9447 KiB

Open AccessArticle

Geopolymers Manufactured by the Alkali Activation of Mining and Ceramic Wastes Using a Potential Sustainable Activator from Olive Stone Bottom Ashes

by Raul Carrillo Beltran, Elena Picazo Camilo, Griselda Perea Toledo and Francisco Antonio Corpas Iglesias

Materials 2025, 18(3), 688; https://doi.org/10.3390/ma18030688 - 4 Feb 2025

Cited by 1 | Viewed by 726

Abstract

The reuse of by-products as alternative raw materials to traditional construction materials is required in order to ensure sustainable development in the construction sector and is a significant and important focus in the fields of materials science. This study developed geopolymers using by-products [...] Read more.

The reuse of by-products as alternative raw materials to traditional construction materials is required in order to ensure sustainable development in the construction sector and is a significant and important focus in the fields of materials science. This study developed geopolymers using by-products from mining, ceramics, and olive industries, including slate stone cutting sludge (SSCS) and chamotte (CH) as aluminosilicate sources, and olive biomass bottom ash (OSBA) as an alkaline activator with sodium silicate. A key novelty of the research lies in the use of SSCS, an underexplored by-product in geopolymerization studies, as a viable aluminosilicate source. The geopolymers were prepared with varying weight ratios of SSCS, CH, and OSBA/Na₂SiO₃ (1.7, 1.9, 2.2, and 2.4). Physical and mechanical tests determined the optimal formulation, while FTIR and SEM analyses revealed the material’s chemical and structural evolution. The FTIR analysis detected the quartz and carbonate phases, indicating incomplete quartz dissolution and carbonate formation during calcination. The SEM analysis revealed a dense microstructure with reduced porosity and enhanced geopolymerization in samples with higher OSBA content. The optimal geopolymer (60% OSBA, 30% CH, OSBA/Na₂SiO₃ ratio of 2.2) achieved a compressive strength of 33.1 MPa after 28 days. These findings demonstrate the feasibility of producing geopolymers using SSCS, CH, and OSBA, promoting the reuse of industrial by-products as sustainable alternatives to conventional binders. Full article

(This article belongs to the Special Issue Advances in Function Geopolymer Materials)

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16 pages, 3603 KiB

Open AccessArticle

Synthesis and Characterization of Metakaolin–Wollastonite Geopolymer Foams for Removal of Heavy Metal Ions from Water

by Mazen Alshaaer, Bader Alharbi, Obaid Alqahtani, Mohammed S. Alotaibi, Abdullah Alzayed and Juma’a Al-Kafawein

Materials 2025, 18(3), 678; https://doi.org/10.3390/ma18030678 - 4 Feb 2025

Viewed by 1071

Abstract

Over the past few decades, researchers have focused on developing new compositions and preparation techniques for geopolymers, as multifunctional products, to optimize their characteristics for use in multiple applications. Therefore, this paper investigates metakaolin geopolymer foam and introduces new geopolymer foams based on [...] Read more.

Over the past few decades, researchers have focused on developing new compositions and preparation techniques for geopolymers, as multifunctional products, to optimize their characteristics for use in multiple applications. Therefore, this paper investigates metakaolin geopolymer foam and introduces new geopolymer foams based on hybrid metakaolin and wollastonite mineral precursors for water purification. The geopolymer foams were prepared using an alkaline activator, mineral-based powders (wollastonite and metakaolin), a foaming agent (aluminum powder), and a foam stabilizer (olive oil). In addition to mechanical tests and assessments of the adsorption capacity of heavy metal ions, the geopolymer foams were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). The geopolymer foams exhibited unique pore structures, containing four classes of pore networks with diameters around 1000 µm, 25 µm, 3 µm, and a well-arranged mesopore network of 50 nm. The utilization of wollastonite (CaSiO₃) alongside metakaolin as a hybrid precursor led to fundamental changes in the composition of the geopolymer binders: a new crystal phase, Ca₅(SiO₄)₂(OH)₂, was formed, and the Si-Al-Na crystal phase disappeared, which led to an increase in the amorphous phase from 87% to 92%. The adsorption rate of heavy metal ions, namely Cr, Co, Cu, Zn, Pd, and As, increased upon introducing wollastonite as a precursor, with absorption rates ranging from 11% to 68%. The findings also revealed that wollastonite significantly increased the geopolymers foams’ compressive strength and elastic modulus from 30 KPa to 67 KPa and from 31 MPa to 126 MPa, respectively. Full article

(This article belongs to the Special Issue Advances in Function Geopolymer Materials)

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14 pages, 7456 KiB

Open AccessArticle

Application of a Generalized Utility Function to Determine the Optimal Composition of Geopolymer Mortar

by Maja Kępniak, Faustyn Recha and Piotr Prochoń

Materials 2024, 17(24), 6237; https://doi.org/10.3390/ma17246237 - 20 Dec 2024

Cited by 1 | Viewed by 496

Abstract

The aim of the presented research was to evaluate the impacts of modifications to the technical properties of fly ash-based geopolymer composites, particularly focusing on enhancing the thermal insulation. Through the utilization of a generalized utility function, optimal dosages of additives such as [...] Read more.

The aim of the presented research was to evaluate the impacts of modifications to the technical properties of fly ash-based geopolymer composites, particularly focusing on enhancing the thermal insulation. Through the utilization of a generalized utility function, optimal dosages of additives such as perlite sand, waste perlite powder, and cenospheres were determined. The study aimed to increase the thermal insulation of the composites while maintaining satisfactory compressive and flexural strength. The results indicated that dosages of perlite dust and cenospheres significantly influenced the technical characteristics of the composites; an exception was the flexural strength, for which these modifications did not show a statistically significant effect. The average compressive strength values, except for the mixes with poor workability, were at least 3.5 MPa (RILEM class II). Notably, a balanced dosage of additives, around 75 kg per cubic meter of the mixture in the total mixture, yielded the most favorable outcomes in terms of thermal isolation (0.18–0.24 W/(m·K) and workability (cone immersion 40–70 mm). Additionally, perlite dust emerged as a potentially superior modifier due to its waste origin. However, further analysis considering life cycle parameters including the carbon footprint and water footprint would be necessary to validate this claim. Overall, the study highlights the potential of utilizing perlite-based modifiers to enhance the thermal insulation of geopolymers while addressing environmental concerns. Full article

(This article belongs to the Special Issue Advances in Function Geopolymer Materials)

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21 pages, 20184 KiB

Open AccessArticle

The Effect of Oil Additives on the Properties of Fly Ash-Based Foamed Geopolymers

by Barbara Kozub, Jan Dudek and Mykola Melnychuk

Materials 2024, 17(23), 5819; https://doi.org/10.3390/ma17235819 - 27 Nov 2024

Cited by 1 | Viewed by 749

Abstract

Geopolymers are a modern class of construction materials that show significant potential for sustainable development, especially through the use of industrial wastes such as fly ash. This study investigated the effect of different oil additives on the properties of fly ash-based geopolymers, with [...] Read more.

Geopolymers are a modern class of construction materials that show significant potential for sustainable development, especially through the use of industrial wastes such as fly ash. This study investigated the effect of different oil additives on the properties of fly ash-based geopolymers, with particular emphasis on the use of both new and used oils. Test samples were prepared using class F fly ash and a 10-molar solution of sodium hydroxide and an aqueous solution of sodium silicate. Oil additives were added at 5%, 10% and 15% by weight. The physical and mechanical properties of the samples were assessed by measuring density, thermal conductivity, compressive and flexural strength, and by analyzing porosity and microstructure. The results showed that oil additives significantly affected the pore structure and mechanical properties of the geopolymers. Furthermore, the type and condition of the used oil determined the mechanical properties, including compressive and flexural strength. Research indicates the possibility of using oils as additives to geopolymers, which helps improve their physical properties and promotes sustainable development through recycling oil waste. Full article

(This article belongs to the Special Issue Advances in Function Geopolymer Materials)

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17 pages, 5027 KiB

Open AccessArticle

A New Performance-Based Test for Assessing Chloride-Induced Reinforcement Corrosion Resistance of Geopolymer Mortars

by Kazuo Ichimiya, Rieru Yamamoto, Ko Ikeda, Quang Dieu Nguyen and Arnaud Castel

Materials 2024, 17(21), 5162; https://doi.org/10.3390/ma17215162 - 23 Oct 2024

Viewed by 1040

Abstract

The widespread adoption of geopolymer concretes in the industry has been slow, mainly due to concerns over their long-term performance and durability. One of the main causes of concrete structures’ deterioration is chloride-induced corrosion of the reinforcement. The reinforcement corrosion process in concrete [...] Read more.

The widespread adoption of geopolymer concretes in the industry has been slow, mainly due to concerns over their long-term performance and durability. One of the main causes of concrete structures’ deterioration is chloride-induced corrosion of the reinforcement. The reinforcement corrosion process in concrete is composed of two main stages: the initiation phase, which is the amount of time required for chloride ions to reach the reinforcement, and the propagation phase, which is the active phase of corrosion. The inherent complexities associated with the properties of precursors and type of activators, and with the multi-physics processes, in which different transfer mechanisms (moisture, chloride, oxygen, and charge transfer) are involved and interact with each other, have been a major obstacle to predicting the durability of reinforced alkali-activated concretes in chloride environments. Alternatively, the durability of alkali-activated concretes can be assessed through testing. However, the performance-based tests that are currently available, such as the rapid chloride permeability test, the migration test or the bulk diffusion test, are only focusing on the initiation phase of the corrosion process. As a result, existing testing protocols do not capture every aspect of the material performance, which could potentially lead to misleading conclusions, particularly when involving an electrical potential to reduce the testing time. In this paper, a new performance-based test is proposed for assessing the performance of alkali-activated concretes in chloride environments, accounting for both the initiation and propagation phases of the corrosion process. The test is designed to be simple and to be completed within a reasonable time without involving any electrical potential. Full article

(This article belongs to the Special Issue Advances in Function Geopolymer Materials)

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14 pages, 6710 KiB

Open AccessArticle

Synthesis and Characterization of Novel Hybrid Wollastonite–Metakaolin-Based Geopolymers

by Mazen Alshaaer and Abdulaziz O. S. Alanazi

Materials 2024, 17(17), 4338; https://doi.org/10.3390/ma17174338 - 2 Sep 2024

Cited by 3 | Viewed by 1352

Abstract

Over the past few decades, researchers have focused on developing new production methods for geopolymers to improve their properties for use in multiple applications as a functional material. This study introduces a new geopolymer system based on wollastonite and metakaolin as precursors. The [...] Read more.

Over the past few decades, researchers have focused on developing new production methods for geopolymers to improve their properties for use in multiple applications as a functional material. This study introduces a new geopolymer system based on wollastonite and metakaolin as precursors. The role of wollastonite was also explored alongside metakaolin in geopolymers. Geopolymers were synthesized by adding wollastonite to metakaolin in different ratios: 0 wt.%, 12.5 wt.%, 25 wt.%, and 50 wt.%. The alkaline activator was then mixed with the powder, wollastonite, and metakaolin to prepare the geopolymers. In addition to mechanical tests, the hardened geopolymers were characterized using XRD, TGA, and SEM techniques. The findings revealed that adding wollastonite in amounts of 0 wt.%–12.5 wt.% did not affect the strength of the geopolymers. Increasing wollastonite between 25 wt.% and 50 wt.% significantly increased the geopolymers’ flexural and compressive strength from 3 MPa to 12.3 MPa and from 23 MPa to 54 MPa, respectively. The use of wollastonite as a precursor also led to fundamental changes in the microstructural structure of the geopolymer matrix: a new crystal phase, (Ca₅(SiO₄)₂(OH)₂), calciochondrodite was formed, and the Si-Al-Na crystal phase disappeared, leading to significant changes in the amorphous phase. Full article

(This article belongs to the Special Issue Advances in Function Geopolymer Materials)

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13 pages, 2791 KiB

Open AccessArticle

A Study on the Shrinkage and Compressive Strength of GGBFS and Metakaolin Based Geopolymer under Different NaOH Concentrations

by Yen-Chun Chen, Wei-Hao Lee, Ta-Wui Cheng and Yeou-Fong Li

Materials 2024, 17(5), 1181; https://doi.org/10.3390/ma17051181 - 3 Mar 2024

Cited by 1 | Viewed by 1804

Abstract

Geopolymers (GPs) are gaining prominence due to their low carbon emissions and sustainable attributes. However, one challenge with GPs, particularly those made with ground granulated blast furnace slag (GGBFS), is their significant shrinkage during the geopolymerization process, limiting its practical applicability. This study [...] Read more.

Geopolymers (GPs) are gaining prominence due to their low carbon emissions and sustainable attributes. However, one challenge with GPs, particularly those made with ground granulated blast furnace slag (GGBFS), is their significant shrinkage during the geopolymerization process, limiting its practical applicability. This study focuses on how the substitution ratio of metakaolin (MK) and the concentration of sodium hydroxide (NaOH) in the activator can influence the shrinkage and strength of a GGBFS-based GP. The experimental approach employed a 3 × 3 parameter matrix, which varied MK substitution ratios (0%, 50%, and 100%) and adjusted the NaOH concentration (6 M, 10 M, and 14 M). The results revealed that increasing MK substitution, particularly with 6 M NaOH activation, reduced the GP shrinkage but also diminished compressive strength, requiring higher NaOH concentrations for strength improvement. Statistical tools, including analysis of variance (ANOVA) and second-order response surface methodology (RSM), were employed for analysis. ANOVA results indicated the significant impacts of both the MK content and NaOH concentration on compressive strength, with no observable interaction. However, the shrinkage exhibited a clear interaction between MK content and NaOH concentration. The RSM model accurately predicted compressive strength and shrinkage, demonstrating a high predictive accuracy, for which the coefficients of determination (R²) were 0.99 and 0.98, respectively. The model provides a reliable method for determining the necessary compressive strength and shrinkage for GGBFS-based GP based on MK substitution and NaOH concentration. Within the optimization range, the RSM model compared with experimental results showed a 6.04% error in compressive strength and 0.77% error in shrinkage for one interpolated parameter set. This study establishes an optimized parameter range ensuring a GP performance that is comparable to or surpassing OPC, with a parameter set achieving a compressive strength of 34.9 MPa and shrinkage of 0.287% at 28 days. Full article

(This article belongs to the Special Issue Advances in Function Geopolymer Materials)

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14 pages, 6498 KiB

Open AccessArticle

The Effect of Mineral Wool Fiber Additive on Several Mechanical Properties and Thermal Conductivity in Geopolymer Binder

by Beata Łaźniewska-Piekarczyk and Dominik Smyczek

Materials 2024, 17(2), 483; https://doi.org/10.3390/ma17020483 - 19 Jan 2024

Cited by 1 | Viewed by 1529

Abstract

The article discusses the effect of additives of waste mineral wool fibers on geopolymer binder. This is an important study in terms of the possibility of recycling mineral wool waste. The paper describes an effective method for pulverizing the wool and the methodology [...] Read more.

The article discusses the effect of additives of waste mineral wool fibers on geopolymer binder. This is an important study in terms of the possibility of recycling mineral wool waste. The paper describes an effective method for pulverizing the wool and the methodology for forming geopolymer samples, labeled G1 for glass-wool-based geopolymer and G2 for stone-wool-based geopolymer. The compressive and flexural strengths and thermal conductivity coefficient of the geopolymer with the addition of mineral fibers were determined. The key element of the article is to verify whether the addition of mineral wool fibers positively affects the properties of the geopolymer. The results obtained prove that the addition of fibers significantly improves the flexural strength. For the G1 formulation, the ratio of compressive strength to flexural strength is 18.7%. However, for G2 samples, an even better ratio of compressive strength to flexural strength values of 26.3% was obtained. The average thermal conductivity coefficient obtained was 1.053 W/(m·K) for the G1 series samples and 0.953 W/(m·K) for the G2 series samples. The conclusions obtained show a correlation between the porosity and compressive strength and thermal conductivity coefficient. The higher the porosity, the better the thermal insulation of the material and the weaker the compressive strength. Full article

(This article belongs to the Special Issue Advances in Function Geopolymer Materials)

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13 pages, 6440 KiB

Open AccessArticle

Cyclic Load Impact Assessment of Long-Term Properties in Compression to Steel and Polyvinyl Alcohol Fibre-Reinforced Geopolymer Composites

by Rihards Gailitis, Andina Sprince, Michał Łach, Pavels Gavrilovs and Leonids Pakrastins

Materials 2023, 16(18), 6128; https://doi.org/10.3390/ma16186128 - 8 Sep 2023

Cited by 1 | Viewed by 1301

Abstract

This study investigates the cyclic load application impact on fly-ash-based geopolymer composites that are reinforced with a low amount of fibre reinforcement. For reinforcement purposes, polyvinyl alcohol and steel fibres are used. For testing purposes, four geopolymer composite mixes were made, three of [...] Read more.

This study investigates the cyclic load application impact on fly-ash-based geopolymer composites that are reinforced with a low amount of fibre reinforcement. For reinforcement purposes, polyvinyl alcohol and steel fibres are used. For testing purposes, four geopolymer composite mixes were made, three of which had fibre reinforcement. Simultaneously, specimens were tested for shrinkage, static-load-induced creep, and cyclic-load-induced creep. For static and cyclic creep testing, specimens were loaded with 20% of their strength. For cyclic creep testing, load application and release cycles were seven days long. When each cycle was introduced, the load was applied in steps. Necessary load application or unloading lasted for 5 min and consisted of four steps, each 25% of the necessary load. From the long-term static and cyclic creep tests, it was seen that only the plain specimens showed that static creep strains are within cyclic creep strains. For all the other specimens, the static load was higher than the cyclic-load-induced creep amplitude. Also, 1% polyvinyl alcohol fibre-reinforced specimens showed the most elastic characteristics under cyclic load, and 1% steel fibre-reinforced specimens appeared to be the most resistant to the cyclic load introduction. Full article

(This article belongs to the Special Issue Advances in Function Geopolymer Materials)

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14 pages, 5889 KiB

Open AccessArticle

Investigations on Stability of Polycarboxylate Superplasticizers in Alkaline Activators for Geopolymer Binders

by Stephan Partschefeld, Adrian Tutal, Thomas Halmanseder, Jens Schneider and Andrea Osburg

Materials 2023, 16(15), 5369; https://doi.org/10.3390/ma16155369 - 31 Jul 2023

Cited by 6 | Viewed by 2402

Abstract

Calcined clays are interesting starting materials to be used as SCMs (supplementary cementitious materials) in cements or to be converted to geopolymers by activation with a high alkaline activator. The adjustment of the properties in the fresh state, especially regarding the consistency of [...] Read more.

Calcined clays are interesting starting materials to be used as SCMs (supplementary cementitious materials) in cements or to be converted to geopolymers by activation with a high alkaline activator. The adjustment of the properties in the fresh state, especially regarding the consistency of these binders, is almost exclusively achieved by the addition of water, since commercially available superplasticizers seem to be ineffective in low-calcium geopolymer systems. The aim of this study was a systematic investigation of various PCE (polycarboxylate ester/ether) superplasticizers (methacrylate ester PCE: MPEG, isoprenol ether PCE: IPEG, methallyl ether PCE: HPEG) with respect to their stability in different alkaline activators (NaOH, KOH, sodium and potassium silicate solutions). The effectiveness of superplasticizers (SPs) in low-calcium geopolymer binders was verified by rheological tests. Size exclusion chromatography was used to investigate if structural degradation of the superplasticizers occurs. The investigated PCE superplasticizers showed a thickening effect in the low-calcium geopolymer system. Depending on the alkalinity of the activator solution, a degradation process was detected for all the PCEs investigated. The side chains of the PCEs are cleaved off the backbone by basic ester and ether hydrolysis. The highest degree of degradation was found in sodium and potassium silicate solutions. In alkaline hydroxide solutions, the degradation process increases with increasing alkalinity. Full article

(This article belongs to the Special Issue Advances in Function Geopolymer Materials)

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Review

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24 pages, 2522 KiB

Open AccessReview

Review of Geopolymer Nanocomposites: Novel Materials for Sustainable Development

by Anna Drabczyk, Sonia Kudłacik-Kramarczyk, Kinga Korniejenko, Beata Figiela and Gabriel Furtos

Materials 2023, 16(9), 3478; https://doi.org/10.3390/ma16093478 - 29 Apr 2023

Cited by 21 | Viewed by 3565

Abstract

The demand for geopolymer materials is constantly growing. This, in turn, translates into an increasing number of studies aimed at developing new approaches to the methodology of geopolymer synthesis. The range of potential applications of geopolymers can be increased by improving the properties [...] Read more.

The demand for geopolymer materials is constantly growing. This, in turn, translates into an increasing number of studies aimed at developing new approaches to the methodology of geopolymer synthesis. The range of potential applications of geopolymers can be increased by improving the properties of the components. Future directions of studies on geopolymer materials aim at developing geopolymers showing excellent mechanical properties but also demonstrating significant improvement in thermal, magnetic, or sorption characteristics. Additionally, the current efforts focus not only on the materials’ properties but also on obtaining them as a result of environment-friendly approaches performed in line with circular economy assumptions. Scientists look for smart and economical solutions such that a small amount of the modifier will translate into a significant improvement in functional properties. Thus, special attention is paid to the application of nanomaterials. This article presents selected nanoparticles incorporated into geopolymer matrices, including carbon nanotubes, graphene, nanosilica, and titanium dioxide. The review was prepared employing scientific databases, with particular attention given to studies on geopolymer nanocomposites. The purpose of this review article is to discuss geopolymer nanocomposites in the context of a sustainable development approach. Importantly, the main focus is on the influence of these nanomaterials on the physicochemical properties of geopolymer nanocomposites. Such a combination of geopolymer technology and nanotechnology seems to be promising in terms of preparation of nanocomposites with a variety of potential uses. Full article

(This article belongs to the Special Issue Advances in Function Geopolymer Materials)

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