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Advances in Function Geopolymer Materials—Second Edition

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A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Construction and Building Materials".

Deadline for manuscript submissions: 10 December 2026 | Viewed by 14153

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Editors

Dr. Michał Łach

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1. Department of Materials Engineering, Faculty of Materials Engineering and Physics, Cracow University of Technology, Jana Pawła II 37, 31-864 Cracow, Poland
2. Interdisciplinary Center for Circular Economy, Cracow University of Technology, Warszawska 24, 31-155 Krakow, Poland
Interests: geopolymer; zeolites; recycling; circular economy; waste immobilization
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Dr. Kinga Korniejenko

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Guest Editor

Institute of Material Engineering, Faculty of Material Engineering and Physics, Cracow University of Technology, Jana Pawła II 37, 31-864 Cracow, Poland
Interests: geopolymer; geopolymer composites; circular economy; additive manufacturing
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Dr. Aleksandar Nikolov

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Institute of Mineralogy and Crystallography, Bulgarian Academy of Science (IMC-BAS), Acad. G. Bonchev Str., bl. 107, 1113 Sofia, Bulgaria
Interests: geopolymer; geopolymer composites; zeolites; antibacterial coatings
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Special Issue Information

Dear Colleagues,

Geopolymer materials classified as inorganic polymers have been known for several decades, but there is currently an increased interest in this type of material. Because geopolymer production technology is sensitive to changes in raw material prices, it is difficult for geopolymers to compete with the prices of conventional mass-produced concretes. However, there is a lot of interest in many specialized, often niche, applications. One example is thermal insulation. Geopolymer materials have a number of unique properties and are classified as functional materials. Thanks to the properly designed syntheses of these materials, it is possible to control various properties. This Special Issue will present the latest achievements and research results on geopolymers as functional materials. We invite all scientists involved in the development of advanced geopolymer binders and concretes as well as advanced geopolymer composites to submit to this issue.

This Special Issue aims to attract original contributions in topics related to advanced functions of geopolymers. We believe that this collection will summarize the current state of the art and featured trends in this field and will thus be a source of new ideas for future research.

Dr. Michał Łach
Dr. Kinga Korniejenko
Dr. Aleksandar Nikolov
Guest Editors

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Keywords

geopolymer
functional material
modern insulation material
sustainable development
innovation in building materials

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Published Papers (8 papers)

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Research

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32 pages, 3603 KB

Open AccessArticle

Air-Void Stability in Self-Compacting Concrete: Linking Fresh-Air Retention with Hardened Pore Structure Through a Synthetic Dispersion Approach

by Beata Łaźniewska-Piekarczyk, Patrycja Miera and Mateusz Moskal

Materials 2026, 19(13), 2730; https://doi.org/10.3390/ma19132730 (registering DOI) - 25 Jun 2026

Abstract

Air entrainment in self-compacting concrete (SCC) is governed by coupled interactions between chemical admixtures, empirical workability behaviour, aggregate-skeleton geometry and early air-bubble stability. In highly flowable mixtures, the hardened air-void system cannot be assessed reliably from total air content alone because bubble escape, redistribution and coalescence in the fresh state may change the final pore structure. This study evaluates the link between early fresh-air retention and hardened air-void characteristics in 25 SCC mixtures arranged according to a five-level Graeco-Latin square design. The analysed factors were air-entraining admixture (AEA) dosage (0.00–0.20% by mass of cement), binder type, water-to-binder ratio (0.29–0.41) and the volumetric paste-to-aggregate filling parameter φ (1.1–1.5). The aggregate skeleton was kept constant to separate paste-composition and volumetric-filling effects from aggregate grading. Fresh concrete was characterised by slump-flow diameter, T₅₀ flow time, density and air content after 5 and 15 min; these quantities were treated as empirical workability and early-retention indicators, not as direct rheological parameters. Hardened concrete was examined after 28 days according to EN 480-11 using total hardened air content A, spacing factor L, micropore content A₃₀₀ and specific surface α. The slump-flow diameter ranged from 50 to 79 cm, fresh air content after 5 min from 1.6% to 8.6%, air loss between 5 and 15 min from 0.41 to 1.12 percentage points, hardened air content from 1.20% to 8.59%, and spacing factor from 0.13 to 0.44 mm. Strong correlations were obtained between fresh and hardened air contents (A₅ vs. A: r = 0.920, R² = 0.846, p < 0.001, 95% CI for r: 0.824–0.964; A₁₅ vs. A: r = 0.922, R² = 0.849, p < 0.001, 95% CI for r: 0.828–0.965), while hardened air content was strongly and inversely related to spacing factor (A vs. L: r = −0.907, R² = 0.822, p < 0.001, 95% CI for r: −0.958 to −0.797). The recalculated ANOVA showed that statistical significance was response-dependent: w/b was significant for early air loss ΔA (F = 4.190, p = 0.040, partial η² = 0.677) and micropore content A₃₀₀ (F = 4.058, p = 0.044, partial η² = 0.670), whereas binder type showed near-threshold tendencies for fresh and hardened air contents. No single factor was statistically significant for all air-void descriptors. The SDI-based approach is therefore presented as a bounded explanatory framework, not as an externally validated prediction model. Direct durability claims, including freeze–thaw resistance, require separate experimental verification. Full article

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

14 pages, 3213 KB

Open AccessArticle

Impacts of Real-Time Aging on Kaolinite-Based Geopolymers in Ambient and Immersion Conditions

by Mazen Alshaaer, Juma’a Al-Kafawein, Sultan Almuaythir and Jan Wastiels

Materials 2026, 19(11), 2325; https://doi.org/10.3390/ma19112325 - 1 Jun 2026

Viewed by 262

Abstract

This study explores the real-time aging of a 15-year-old uncalcined kaolinite-based geopolymer (UKG). The significance of this research lies in the fact that uncalcined kaolinite-based geopolymer is a relatively new material tailored for diverse applications, including construction, water treatment, and waste stabilization. While some studies have investigated its durability through accelerated tests, observing its aging over 15 years is essential for its commercial use and field deployment. The specimens were prepared from kaolinite, silica sand, sodium hydroxide, and water. The mixture was molded, compacted, and cured at 80 °C for 24 h to produce a stable geopolymer. Some samples were stored under ambient conditions, while others were immersed; both groups were left for 15 years. After this period, tests evaluated their mechanical, physical, and microstructural properties using XRD, EDS, and SEM. The samples stored under ambient conditions exhibited properties comparable to those of the unaged specimens. In contrast, the immersed samples were unstable, experienced mass loss, showed a sharp decline in strength, and displayed significant microstructural and phase changes. This study suggests adding an extra curing step, such as steaming (hydrothermal) or immersion in alkaline solutions, to enhance the long-term stability of geopolymer binder under immersion conditions. Full article

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

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10 pages, 1645 KB

Open AccessArticle

Degradation of Geopolymers by Oxalic Acid: A Kinetic Study

by José Ramón Gasca-Tirado, Juan Carlos Ramírez Granados, Manuel Aguilar-Franco, Héctor R. Guzmán-Carrillo, Karen M. Soto, José Mauricio López-Romero, Eric M. Rivera-Muñoz and Alejandro Manzano-Ramírez

Materials 2026, 19(4), 748; https://doi.org/10.3390/ma19040748 - 14 Feb 2026

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Abstract

The increasing need for sustainable construction materials has prompted research into alternatives to Ordinary Portland Cement (OPC), a major contributor to global CO₂ emissions. Geopolymers, synthesized via alkali activation of aluminosilicate precursors such as metakaolin and fly ash, are a promising alternative, reducing up to 80% of carbon emissions. However, their long-term durability in aggressive chemical environments, particularly when up against organic acids, remains insufficient. While mineral and inorganic acid resistance have been studied, the impact of naturally occurring organic acids like oxalic acid (Ox)—commonly found in soils and organic-rich sediments—has received limited attention. Ox is known to chelate metal ions and alter mineral phases, potentially affecting the integrity of geopolymer matrices. This study investigates the degradation behavior of geopolymers under continuous exposure to Ox (0.2, 0.4, and 0.6 M) at 25 °C using a flow-through reactor. Mass loss over time was monitored to determine reaction kinetics, while SEM, FT-IR, XRD, and EDS analyses were conducted to evaluate microstructural and chemical changes. The results revealed significant alterations in the geopolymers’ structures due to Ox exposure, providing key insights into their vulnerability to organic acid attack. These findings indicate the importance of considering organic acid interactions in long-term performance assessments of geopolymers. Full article

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

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14 pages, 1148 KB

Open AccessArticle

High-Capacity Adsorption of a Cationic Dye Using Alkali-Activated Geopolymers Derived from Agricultural Residues

by Claudia Alejandra Hernández-Escobar, América Susana Mares-García, Miguel Alonso Orozco-Alvarado, Alejandro Vega-Rios, Claudia Ivone Piñón-Balderrama, Anayansi Estrada-Monje and Erasto Armando Zaragoza-Contreras

Materials 2026, 19(1), 177; https://doi.org/10.3390/ma19010177 - 3 Jan 2026

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Abstract

A geopolymer, derived from agricultural waste, was used as an efficient, sustainable, and low-cost adsorbent of methylene blue, a recurrent industrial dye contaminant. The geopolymer was synthesized via a standard alkali activation process using wheat husk ash calcinated at 1050 °C. Adsorption capabilities were evaluated through batch kinetic experiments. The removal efficiency was determined by ultraviolet–visible spectrophotometry, and the adsorption kinetics were fitted to various models. The geopolymer demonstrated a maximum adsorption capacity of 270.58 mg/g for methylene blue, achieving a removal efficiency of 85.20% under optimal conditions. Kinetic analysis confirmed that the adsorption process is best described by the pseudo-second-order model. This suggests that chemisorption, which involves chemical bonding or electron exchange between the dye and the negatively charged aluminosilicate structure of the geopolymer, is the rate-limiting mechanism. This demonstrates that geopolymers are effective and promising adsorbents, valorizing an agricultural waste stream into a functional material for the efficient treatment of dye-polluted wastewater. The competitive capacity and favorable chemisorption mechanism position the geopolymer as a promising material for the remediation of dye-contaminated industrial effluents. Full article

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

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31 pages, 25510 KB

Open AccessArticle

Geopolymer Foams Loaded with Diatomite/Paraffin Granules for Enhanced Thermal Energy Storage

by Agnieszka Przybek

Materials 2025, 18(19), 4512; https://doi.org/10.3390/ma18194512 - 28 Sep 2025

Cited by 4 | Viewed by 1366

Abstract

This paper presents the development and characteristics of geopolymer foams modified with paraffin-based phase change materials (PCMs) encapsulated in diatomite. The aim was to increase both the thermal insulation and heat storage capacity of the foams while maintaining sufficient mechanical strength for construction applications. Eleven variants of composites with different PCM fractions (5–10% by mass) and grain sizes (<1.6 mm to >2.5 mm) were synthesized and tested. The inclusion of PCM encapsulated in diatomite modified the porous structure: the total porosity increased from 6.6% in the reference sample to 19.6% for the 1.6–1.8 mm_10% wt. variant, with pore diameters ranging from ~4 to 280 µm. Thermal conductivity (λ) ranged between 0.090–0.129 W/m·K, with the lowest values observed for composites 2.0–2.5 mm_5–10% wt. (≈0.090–0.091 W/m·K), which also showed high thermal resistance (R ≈ 0.287–0.289 m²·K/W). The specific heat (Cp) increased from 1.28 kJ/kg·K (reference value) to a maximum value of 1.87 kJ/kg·K for the 2.0–2.5 mm_10% mass variant, confirming the effective energy storage capacity of PCM-modified foams. Mechanical tests showed compressive strength values in the range of 0.7–3.1 MPa. The best structural performance was obtained for the 1.6–1.8 mm_10% wt. variant (3.1 MPa), albeit with a higher λ (≈0.129 W/m·K), illustrating the classic trade-off between porosity-based insulation and mechanical strength. SEM microstructural analysis and mercury porosimetry confirmed the presence of mesopores, which determine both thermal and mechanical properties. The results show that medium-sized PCM fractions (1.6–2.0 mm) with moderate content (≈10% by weight) offer the most favorable compromise between insulation and strength, while thicker fractions (2.0–2.5 mm) maximize thermal energy storage capacity. These findings confirm the possibility of incorporating natural PCMs into geopolymer foams to create multifunctional materials for sustainable and energy-efficient building applications. A unique contribution to this work is the use of diatomite as a natural PCM carrier, ensuring stability, compatibility, and environmental friendliness compared to conventional encapsulation methods. Full article

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

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24 pages, 3402 KB

Open AccessArticle

Development of Multifunctional Slag and Bauxite Residue-Based Geopolymers with Heavyweight Aggregate Enhancement

by Andrie Harmaji, Reza Jafari and Guy Simard

Materials 2025, 18(17), 4087; https://doi.org/10.3390/ma18174087 - 1 Sep 2025

Viewed by 1452

Abstract

The growing demand for sustainable and multifunctional construction materials, particularly those capable of addressing durability and energy challenges, has motivated the development of conductive and photothermally active geopolymers. This study investigated the use of an Fe-rich spinel aggregate (FSA) as a high-density filler in geopolymers composed of ground granulated blast furnace slag and bauxite residue, with a fixed addition of 1 wt% graphite (binder-based) to enhance electrical conductivity. The effects of different FSA replacement percentages (0–100%) on compressive strength, electrical conductivity, photothermal efficiency, and chemical resistance were evaluated. An increase in the FSA content translated to an increase in the final compressive strength, with 100% FSA replacement achieving the highest value of 45.5 ± 2.5 MPa at 28 days. As the FSA content increased, the electrical resistivity decreased to as low as 42 Ω·m at 100% replacement. Under simulated solar flux conditions (1 kW/m²), photothermal analysis revealed that the 100% FSA mixtures exhibited the highest surface temperature increase of 9.8 °C after 300 s, indicating their superior thermal responsiveness. Furthermore, acid immersion in 10% HCl for 28 days showed mass gain in all geopolymers, with the highest gain observed at 50% FSA (+11.51%). Similarly, the strength increased after acid exposure up to a 75% FSA content. These findings highlight the multifunctional potential of FSA-enhanced geopolymers for high-mechanical-performance, electrically conductive, photothermally active, and chemically durable materials as multifunctional construction materials. Full article

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

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30 pages, 10507 KB

Open AccessArticle

Thermal Properties of Geopolymer Concretes with Lightweight Aggregates

by Agnieszka Przybek, Paulina Romańska, Kinga Korniejenko, Krzysztof Krajniak, Maria Hebdowska-Krupa and Michał Łach

Materials 2025, 18(13), 3150; https://doi.org/10.3390/ma18133150 - 3 Jul 2025

Cited by 15 | Viewed by 3665

Abstract

Despite the availability of various materials for chimney applications, ongoing research seeks alternatives with improved thermal and chemical resistance. Geopolymers are a promising solution, exhibiting exceptional resistance to high temperatures, fire, and aggressive chemicals. This study investigates fly ash-based lightweight geopolymer concretes that incorporate expanded clay aggregate (E.C.A.), perlite (P), and foamed geopolymer aggregate (F.G.A.). The composites were designed to ensure a density below 1200 kg/m³, reducing overall weight while maintaining necessary performance. Aggregate content ranged from 60 to 75 wt.%. Physical (density, thickness, water absorption), mechanical (flexural and compressive strength), and thermal (conductivity, resistance) properties were evaluated. F.G.A. 60 achieved a 76.8% reduction in thermal conductivity (0.1708 vs. 0.7366 W/(m·K)) and a 140.4% increase in thermal resistance (0.1642 vs. 0.0683). The F.G.A./E.C.A./P 60 mixture showed the highest compressive strength (18.069 MPa), reaching 52.7% of the reference concrete’s strength, with a 32.3% lower density (1173.3 vs. 1735.0 kg/m³). Water absorption ranged from 4.9% (REF.) to 7.3% (F.G.A. 60). All samples, except F.G.A. 70 and F.G.A. 75, endured heating up to 800 °C. The F.G.A./E.C.A./P 60 composite demonstrated well-balanced performance: low thermal conductivity (0.2052 W/(m·K)), thermal resistance up to 1000 °C, flexural strength of 4.386 MPa, and compressive strength of 18.069 MPa. The results confirm that well-designed geopolymer lightweight concretes are suitable for chimney and flue pipe linings operating between 500 and 1000 °C and exposed to acidic condensates and aggressive chemicals. This study marks the initial phase of a broader project on geopolymer-based prefabricated chimney systems. Full article

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

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Review

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43 pages, 4854 KB

Open AccessReview

The Role of Natural Fibers in the Building Industry—The Perspective of Sustainable Development

by Agnieszka Przybek

Materials 2025, 18(16), 3803; https://doi.org/10.3390/ma18163803 - 13 Aug 2025

Cited by 27 | Viewed by 5314

Abstract

Contemporary construction faces the need to reduce its negative impact on the environment, prompting designers, investors, and contractors to seek more sustainable materials and technologies. One area of dynamic development is the use of natural fibers as an alternative to conventional, often synthetic, building components. Plant- and animal-based fibers, such as hemp, flax, jute, straw, bamboo, and sheep’s wool, are characterized by low energy consumption in production, renewability, and biodegradability. Their use is in line with the concept of a circular economy and reduces the carbon footprint of buildings. Natural fibers offer a number of beneficial physical and functional properties, including good thermal and acoustic insulation parameters, as well as hygroscopicity, which allows for the regulation of indoor humidity, improving air quality and comfort of use. In recent years, there has also been a renaissance of traditional building techniques, such as straw construction, often combined with modern engineering standards. Their potential is particularly recognized in green and energy-efficient construction. The article provides an overview of the types of natural fibers available for use in construction and analyzes their technical, environmental, and economic properties. It also draws attention to current regulations, standards, and certifications (e.g., LEED, BREEAM) that promote the popularization of these solutions. In light of the analyzed data, the role of natural fibers as a viable alternative supporting the transformation of the construction sector towards sustainable development is considered. Full article

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

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