Search Results (101)

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

Frequently, the viscous mixture from shield operations is disposed of because its significant water ratio and the presence of polymers like foaming agents result in subpar structural qualities, contributing to the unnecessary consumption of land and the squandering of soil assets. Therefore, these problems urgently need to be solved economically and effectively. This study relies on the shield sludge produced by Qingdao Metro Line 6 project, and sand and shield sludge were used as the raw materials for synchronous grouting. By applying the basic principles of geopolymerization, ingredients like shield sludge and ground granulated blast furnace slag (GGBS) were mixed with sodium hydroxide, serving as the activating agent, in the preparation of the simultaneous grout formulas. A broad range of laboratory tests was conducted to evaluate the performance of these grout formulations. The effects of varying material ratios on key performance indicators—namely, fluidity, water secretion rate, setting time, and 3-day unconfined compressive strength (UCS)—were systematically analyzed. Based on these findings, the optimal material ratios for shield sludge-based synchronous grouting materials were proposed. Subsequently, component geopolymer was prepared from the activated shield sludge and shield sludge without adding any additional alkaline activators by simply adding water. A geopolymer with a 28-day compressive strength of 51.08 MPa was obtained when the shield sludge dosing was 60 wt%. This study aims to provide a reference for the preparation of synchronous grouting materials for the resource utilization of shield sludge. Full article

Geopolymer foam concrete (GFC) is a green, lightweight material produced by introducing bubbles into the geopolymer slurry. The raw materials for GFC are primarily silicon–aluminum-rich minerals or solid waste. Lead–zinc tailings (LZTs), as an industrial solid waste with high silicon–aluminum content, hold significant potential as raw materials for building materials. This study innovatively utilized LZTs to prepare GFC, incorporating MK, GGBS, and alkali activators as silicon–aluminum-rich supplementary materials and using H₂O₂ as a foaming agent, successfully producing GFC with excellent properties. The effects of different LZT content on the pore structure and various macroscopic properties of GFC were comprehensively evaluated. The results indicate that an appropriate addition of LZT effectively optimizes the pore structure, resulting in uniform pore distribution and pore shapes that are more spherical. Spherical pores exhibit better geometric compactness. The optimal LZT content was determined to be 40%, at which the GFC exhibits the best compressive strength, thermal conductivity, and water resistance. At this content, the dry density of GFC is 641.95 kg/m³, the compressive strength reaches 6.50 MPa after 28 days, and the thermal conductivity is 0.176 (W/(m·K)). XRD and SEM analyses indicate that under the combined effects of geopolymerization and hydration reactions, N–A–S–H gel and C–S–H gel were formed. The preparation of GFC using LZTs shows significant potential and research value. This study also provides a feasible scheme for the recycling and utilization of LZTs. Full article

Foamed geopolymer materials are increasingly studied due to their inherent fire resistance. To date, these materials have primarily been produced by casting into moulds, with foaming occurring during mixing or within the moulds, shortly before setting. For practical applications, however, it is advantageous to apply these materials directly onto surfaces with complex geometries. Although several techniques for geopolymer spraying have been described in the literature, many exhibit limitations that restrict their practical implementation. This study presents a novel spraying technology developed on a dedicated process line, enabling in situ dosing of the foaming agent immediately before application. The system integrates infrared heating to ensure controlled curing of the geopolymer. This paper outlines the design of the process line and its core functionalities while presenting selected results of material tests conducted on the obtained geopolymer coatings. Tests performed on approximately 200 m² of surface confirmed the functionality of the process. The thermal conductivity of the sprayed foams was about 0.07 W/m-K. The inclusion of a phase-change material (PCM) in the geopolymers further enhanced their ability to store and regulate thermal energy. The adhesion strength results, consistently exceeding 1 MPa across various substrates (steel, geopolymer, gypsum board), confirmed the practical suitability of the proposed solution. This was also demonstrated by the homogeneous foamed structure obtained. Full article

This study investigates the upcycling of disposable face masks, which were produced in vast quantities during the COVID-19 pandemic and are now widely stockpiled in public institutions, destined for landfills after reaching expiration dates. The research focuses on incorporating shredded mask fibers into geopolymer matrices, evaluating the effects on mechanical and thermal properties to develop sustainable, high-performance materials. This approach addresses critical environmental, social, and economic challenges by transforming problematic waste into valuable resources while promoting sustainable building practices, such as developing insulating products for the construction industry. Mechanical testing demonstrated that adding shredded mask fibers (2 mm and 6 mm in size, up to 5 wt.%) enhanced the flexural strength of geopolymeric products. The optimal performance was achieved by adding 3 wt.% of 2 mm-length fibers, resulting in a flexural strength of 4.56 ± 0.23 MPa. Regarding compressive strength, the highest value (54.78 ± 2.08 MPa) was recorded in geopolymers containing 1 wt.% of 2 mm fibers. Thermal insulation properties of the materials improved with higher mask content, as evidenced by reductions in thermal conductivity, diffusivity, and specific heat. The lowest thermal conductivity values were observed in geopolymers containing 5 wt.% (0.4346 ± 0.0043 W·m⁻¹·K⁻¹) and 3 wt.% (0.6514 ± 0.0002 W·m⁻¹·K⁻¹) of 2 mm mask fibers. To further enhance thermal insulation, geopolymers with 5 wt.% mask fibers were foamed using H₂O₂ to obtain highly porous light materials, obtaining a reduction of thermal conductivity (0.3456 and 0.3710 ± 0.0007 W·m⁻¹·K⁻¹). This research highlights the potential of integrating fibrous waste materials into advanced construction technologies, offering solutions for waste reduction and development in the building sector toward sustainability. Full article

To address the demands of the low-carbon era, this study proposed a solution by using eggshell powder (ESP), fly ash, and ground granulated blast furnace slag together with alkaline solution in the preparation of lightweight geopolymer foam concrete (LWGFC). The aim of this study is to investigate the influence of replacing precursor materials with 5–20% ESP on the expansion behavior, physical, mechanical characteristics, and thermal conductivity of LWGFC. Additionally, the study examines the effect of varying the silicate modulus (SiO₂/Na₂O ratios of 1.0, 1.25, and 1.5) on the properties of LWGFC. Incorporating ESP from 5% to 20% with a constant SiO₂/Na₂O ratio reduced the initial setting time, while a high SiO₂/Na₂O ratio controlled the setting time and expansion volume. The high SiO₂/Na₂O ratio decreased the porosity and enhanced the compressive strength of the LWGFC but increased the thermal conductivity. The inclusion of more than 10% ESP content negatively affected compressive strength; however, a high SiO₂/Na₂O ratio can mitigate this detrimental effect. The thermal conductivity of optimal-content ESP mixtures with a SiO₂/Na₂O ratio of 1.0 was about 0.84 W/m·K, which is 2.1% lower than mixtures with a ratio of 1.25 and 18.6% lower than those with a ratio of 1.5. High-content ESP mixtures had a density of 1707 kg/m³, 0.97 W/m·K, and a compressive strength of 18.9 MPa at a low SiO₂/Na₂O ratio. Finally, the inclusion of ESP in the LWGFC, along with the use of an appropriate silicate modulus, resulted in improved strength development while decreasing porosity. Full article

Membrane technology is widely used in various aspects of wastewater treatment; however, single membrane technology has a series of disadvantages, such as high selectivity, poor recycling performance, and susceptibility to contamination. In this study, a treatment method combining an advanced oxidation process and membrane separation technology was proposed, and a geopolymer-based Fenton-like catalytic tubular membrane (GFM) was prepared by using H₂O₂ as a blowing agent by the direct foaming method. It was shown that the optimum conditions for the preparation of the membrane were a water glass modulus of 1.8 M, the addition of foaming agent of 1 mL, and a thickness of the membrane of 6.5 mm, with a flux of 6942 L·m⁻²·h⁻¹. Due to the characteristics of the tubular membrane, the possibility of adding hydrogen peroxide directly inside the membrane allows an optimal Fenton-like removal, which is better than outside the membrane, thus reducing the consumption of hydrogen peroxide. The tubular membrane has a multi-stage porous structure, high flux, and a high specific surface area (68.74 m²/g). The GFM/H₂O₂ Fenton-like system formed is capable of almost completely degrading all kinds of synthetic dyes under various stringent conditions, and the XRD, FTIR, and TG analyses and cycling tests showed that the GFM has excellent stability and a significant advantage in terms of reusability. Full article

The need for environmentally friendly and energy-efficient building materials has increased significantly. This study synthesizes geopolymer foams with enhanced thermal insulation properties using silica fume and natural zeolite tuff. Zeolite’s porous structure and active sites improve polymerization and strengthen the foam, while silica fume reacts with NaOH to release sodium silicate, forming a durable geopolymer matrix. Foam porosity is introduced by generating oxygen gas from H₂O₂ and NaOH, with calcium stearate stabilizing the foam structure. Comparative analysis of the compressive strength, bulk density, porosity, and thermal conductivity shows that incorporating H₂O₂ and calcium stearate significantly reduces thermal conductivity (from 0.19 to 0.06 W/m·K) while ensuring a highly porous system (66–82.6% porosity) with adequate mechanical strength (1.6–3.39 MPa). These findings highlight the potential of the developed geopolymer foam for sustainable insulation applications. 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