Search Results (44)

In the context of the growing need to reduce greenhouse gas emissions and to develop sustainable solutions for the construction industry, foamed geopolymers represent a promising alternative to traditional binders and insulation materials. This study investigates the thermal properties of novel low-emission, insulating geopolymer binders made from fly ash with diatomite, chalcedonite, and wood wool aiming to assess their potential for use in thermal insulation systems in energy-efficient buildings. The stability of the foamed geopolymer structure is also assessed. Measurements of thermal conductivity, specific heat, microstructure, density, and compressive strength are presented. The findings indicate that the selected geopolymer formulations exhibit low thermal conductivity, high heat capacity and low density, making them competitive with conventional insulation materials—mainly load-bearing ones such as aerated concrete and wood wool insulation boards. Additionally, incorporating waste-derived materials reduces the production carbon footprint. The best results are represented by the composite incorporating all three additives (diatomite, chalcedonite, and wood wool), which achieved the lowest thermal conductivity (0.10154 W/m·K), relatively low density (415 kg/m³), and high specific heat (1.529 kJ/kg·K). Full article

Additive manufacturing has recently become popular and more cost-effective for building construction. This study presents a prospective life cycle assessment (LCA) of 3D-printed foamed geopolymer composites (3D-FOAM materials) incorporating construction and demolition waste. The materials were developed using fly ash, slag, sand, and a foaming agent, with recycled clay brick waste (CBW) and autoclaved aerated concrete waste (AACW) added as alternative raw materials. The material formulations were evaluated for their compressive strength and thermal conductivity to define two functional units that reflect structural and thermal performance. A prospective life cycle assessment (LCA) was conducted under laboratory-scale conditions using the ReCiPe 2016 method. Results show that adding CBW and AACW reduces environmental impacts across several categories, including global warming potential and ecotoxicity, without compromising material performance. Compared to conventional wall systems, the 3D-FOAM materials offer a viable low-impact alternative when assessed on a functional basis. These findings highlight the potential of integrating recycled materials into additive manufacturing to support circular economy goals in the construction sector. Full article

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

Sawdust is receiving increasing attention as a promising green adsorbent. However, due to its powder nature, it is difficult to recover after adsorbing heavy metals and may even cause secondary pollution. To solve this problem, a novel sawdust/foamed geopolymer (SFG) adsorbent was prepared by using sawdust as a raw material, geopolymer as a binder, and hydrogen peroxide as a foaming agent. This study discussed the effect of SFG dosage, solution temperature, solution pH, contact time, and initial Cu²⁺ solution concentration on the adsorption capacity and removal rate. The results showed that a desirable SFG adsorbent with the SFG dosage of 0.5 g, temperature of 25 °C, pH of 5, contact time of 720 min, and initial Cu²⁺ solution concentrations of 90 mg/L is recommended, of which the adsorption capacity is 31.5 mg/g with the removal rate being 92.76%. In addition, the adsorption performance of the SFG adsorbent is superior to that of pure sawdust and similar to that of the foamed geopolymer adsorbent, and it has the characteristics of higher strength, lower cost, and more environmental friendliness. This study indicated that the SFG adsorbents are feasible as adsorbents; meanwhile, this work can provide a scientific reference for the development of new bio-composite adsorbent materials, especially in the field of the treatment of heavy metal ions in wastewater. Full article

The present work is the first study exploring the potential of geopolymer foams based on fayalite slag, an industrial by-product, as the primary precursor, for lightweight and fireproof construction applications. The research involved the synthesis and characterization of geopolymer foams with varying water to solid ratio, followed by testing their physical and mechanical properties. The phase composition and microstructure of the obtained geopolymer foams were examined using powder XRD, Micro-CT and SEM. The geopolymer foams at optimal water to solid ratio (0.15) demonstrated 73.2% relative porosity, 0.92 g/cm³ apparent density and 1.3 MPa compressive strength. The use of an air-entraining admixture improved compressive strength to 2.8 MPa but lowered the relative porosity to 64.5%. Real-size lightweight panel (300 × 300 × 30 mm) specimens were prepared to measure thermal conductivity coefficient (0.243 W/mK) and evaluate size effect and the reaction to direct fire. This study demonstrates the successful preparation of geopolymer foam products containing 81% fayalite slag, highlighting its potential as a lightweight, insulating and fire-resistant material for sustainable construction applications. Full article

Additive manufacturing has been of considerable interest for the last 10 years. Cementitious composites have been developed to ensure fast and effective structure printing. To address sustainability and reduce the environmental impact of Portland cement-based composites, geopolymer composites have been developed that can be printed. This brings us to this study’s aim, which is to allow the printing of recycled lightweight structures with not only the ability to act as a structural material but also insulation capabilities. This study focuses on mix design development and the mechanical strength, creep, and shrinkage properties of these composites. The results show that foamed 3D-printed fly ash-based geopolymer composites may have reduced compressive strength, but still have sufficient strength to be used as a structural material. Furthermore, their creep and shrinkage strain are lower than those of the composite without foaming agent introduction. Full article

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

Geopolymer materials are increasingly being considered as an alternative to environmentally damaging concrete based on Portland cement. The presented work analyzed waste from mines and waste incineration plants as potential precursors for producing geopolymer materials that could be used to make lightweight foamed geopolymers for insulation applications. The chemical and phase composition, radioactivity properties, and leachability of selected precursors were analyzed. Then, geopolymer materials were produced, and their strength properties were examined through compression and flexural tests. The results of the strength tests guided the material selection for foamed geopolymer materials. Next, geopolymer foams were foamed with hydrogen peroxide and aluminum powder. The produced foamed materials were subjected to strength and thermal conductivity tests. The results demonstrated the great potential of mine waste in the synthesis of geopolymers and the production of lightweight geopolymer foams with good insulating properties. Full article

The purpose of this study was to analyze the effects of phase-change components on the properties of geopolymer foams. Geopolymer foams are lightweight foamed geopolymers that are characterized by a high degree of porosity. Phase change materials, on the other hand, are compounds that, when added to a material, allow it to absorb, store, and then release large amounts of energy. Three types of PCMs, i.e., MikroCaps, GR42, and PX25, were introduced at 15% by weight. Geopolymer materials were produced based on silica fly ash, and hydrogen peroxide H₂O₂ was used to foam the geopolymer structure. The PCM geopolymer composites were cured at 60 °C. The produced materials were tested for physical, chemical, and thermal properties. The tests included oxide and mineral composition analysis of the base material, PCM particle size analysis, apparent density and porosity tests on the foams, water leachability tests, thermal tests (λ, Cv, Cp, α), and structural and textural analysis. The most relevant tests to confirm the performance of the phase-change materials were thermal tests. With the introduction of PCMs, volumetric heat capacity increased by as much as 41% and specific heat by 45%, and thermal diffusivity decreased by 23%. The results confirm the great potential of geopolymer composites as modern insulation materials for buildings and structures. Full article

Geopolymers are synthesized using anthropogenic raw materials and waste from the energy industry. Their preparation necessitates an alkaline activator, which facilitates the dissolution of raw materials and their subsequent binding. At present, geopolymers are considered a promising material with the potential to replace conventional cement-based products. This research investigates foamed geopolymer materials based on fly ash, natural fibers, and phase-change materials. The study utilized three distinct types of fibers and two phase-change materials manufactured by Rubitherm Technologies GmbH of Germany. This paper presents the results of the thermal conductivity coefficient and specific heat tests on the finished foams. Additionally, compressive strength tests were conducted on the samples after 28 days. Natural fibers decreased the insulation parameter by 12%, while PCM enhanced it by up to 6%. The addition of fibers increased the compressive strength by nearly 30%, whereas PCM reduced this by as little as 14%. Natural fibers and phase-change materials had an increased heat capacity by up to 35%. The results demonstrated the material’s potential in various industrial sectors, with the primary areas of application being building materials and insulations. The findings illustrate the significant potential of these composites as energetically and environmentally sustainable materials. Full article

Geopolymers are binder materials that are produced by a chemical reaction between silica or aluminum compounds with an alkaline activating solution. Foamed geopolymer materials are increasingly being cited as a viable alternative to popular organic insulation materials. Since the foaming process of geopolymers is difficult to control, and any achievements in improving the performance of such materials are extremely beneficial, this paper presents the effect of the addition of basalt powder on the properties of foamed geopolymers. This paper presents the results of physicochemical studies of fly ash and basalt, as well as mechanical properties, thermal properties, and structure analysis of the finished foams. The scope of the tests included density tests, compressive strength tests, tests of the thermal conductivity coefficient using a plating apparatus, as well as microstructure tests through observations using light and scanning microscopy. Ground basalt was introduced in amounts ranging from 0 to 20% by mass. It was observed that the addition of basalt powder contributes to a reduction in and spheroidization of pores, which directly affect the density and pore morphology of the materials tested. The highest density of 357.3 kg/m³ was characterized by samples with a 5 wt.% basalt powder addition. Their density was 14% higher than the reference sample without basalt powder addition. Samples with 20 wt.% basalt addition had the lowest density, and the density averaged 307.4 kg/m³. Additionally, for the sample containing 5 wt.% basalt powder, the compressive strength exceeded 1.4 MPa, and the thermal conductivity coefficient was 0.1108 W/m × K. The effect of basalt powder in geopolymer foams can vary depending on many factors, such as its chemical composition, grain size, content, and physical properties. The addition of basalt above 10% causes a decrease in the significant properties of the geopolymer. Full article

This paper presents a research program aimed towards developing a method of producing lightweight, porous geopolymer composites for the construction industry based on industrial wastes. A direct method involving the addition of chemicals is currently most commonly used to produce the porous mineral structure of a geopolymer matrix. This relies on a reaction in a highly alkaline environment of the geopolymer to produce a gas (usually hydrogen or oxygen) that forms vesicles and creates a network of pores. This paper demonstrates the feasibility of producing a slag-based geopolymer paste foamed with aluminum powder, taking into account different parameters of fresh paste production: the mixing duration, its speed and the timing of foaming agent addition. The foaming process of the fresh paste in terms of the volumetric changes and temperature development of the fresh paste during the curing of the material are observed. After hardening, the physical properties (density and porosity) as well as the mechanical parameters (compressive strength and work of damage) are determined for the nine manufactured foamed pastes. Image analysis software was used to assess the porosity distribution of the material across the cross-section of the samples. The results enabled the design of the mixing procedure to be adopted during the manufacture of such composites. Full article

The article discusses the fabrication of sandwich steel and geopolymer structures using spray technology without the need for formwork. In the article, the effects of high temperatures on geopolymer materials are analyzed and their mechanical properties and durability are examined. The importance of geopolymer coatings for steel protection is also highlighted, and specific features such as the setting time, application process, attachment strength, fire testing, and production costs are analyzed. The materials and methods used in the study are described, including the composition of geopolymer binders and the process of applying geopolymer coatings to steel plates. The research includes test methods such as strength tests, density tests, thermal conductivity tests, accelerated aging tests, microstructure analyses, pore size analyses, and fire resistance tests. The research section concludes with a summary of the chemical and phase composition of the materials and a discussion of the fire resistance of the geopolymer composites (GCs). The results show that GC foams offer excellent thermal insulation, providing up to 75 min of fire resistance with a 6 mm coating, reducing temperatures by 150 °C compared to uncoated steel. GC foams have a density of 670 kg/m³, a thermal conductivity of 0.153 W/m∙K, and a cost effectiveness of USD 250 per cubic meter. Full article

This study explores the influence of temperature–time conditions, surfactants, and varied waste compositions on the curing of geopolymer gels, a foam formation with the properties of porous geopolymers. Findings reveal that a 6 h curing period leads to a density of 435 kg/m³ and strength of 0.66 MPa, with notable improvements at 12 h. Comparing 12 to 24 h curing, differences in characteristics remain within 5%, highlighting the 12 h period as more energy-efficient. Sodium stearate-based samples exhibit excellent properties, significantly boosting strength while maintaining overall properties. Microwave curing achieves the lowest density (291 kg/m³) and closely parallels properties of samples cured conventionally for 12 h. However, it leads to complete destruction in sodium stearate-modified gels due to the Dumas reaction, making it unsuitable above 200 °C. Optimal properties emerge from compositions using sodium stearate and oven curing, achieving densities of 334 kg/m³ and strengths of 1.08 MPa (Severodvinsk CHPP-1) and 373 kg/m³ and 1.17 MPa (Novocherkassk SDPP). Although microwave curing allows for high energy efficiency, its high temperature demands necessitate careful material selection. This study offers insight into enhancing geopolymer properties while emphasizing the importance of tailored curing methods for sustainable material development. Full article

Waste glass is an endless issue for the majority of the countries in the world with a linear economy of usage of materials. Demolition waste is counted as part of total construction and demolition waste (CDW). Even today, there are some statistical problems with the quantification of demolition waste and dividing it from total CDW, since most countries do not provide such a division of waste types. The current review shows possible ways of utilizing waste glass in some useful products in the construction industry. It is elaborated using PRISMA@ methodology with bibliometric and qualitative methods to provide a systematical overview of the publications in the period from 2000 to 2023. The bibliometric search was handled with the application RStudio© using sources in the biggest database, Scopus. Most of the published research items are mainly focused on using waste glass in concrete applications. However, there are seven possible areas of waste glass application in the construction industry: concrete products, gypsum–cement composites, asphalt or concrete pavement, geopolymer mortars, foamed glass ceramics, glass ceramics, and soil foundation strengthening/stabilization. In its turn, the circular economy should be applied since it provides a prolonged turnaround of materials throughout their life cycle. Full article