Application Of Geopolymer Research Articles

Molecular dynamics simulation of the initial stage induction of alkali-activated aluminosilicate minerals.

With the increasing global concern over carbon emissions, geopolymers have garnered significant attention due to their energy-saving, waste utilization, and eco-friendly advantages. Metakaolin and slag, as aluminum-containing mineral materials in geopolymer production, have been widely studied and applied. Previous research has mainly focused on performance design and theoretical development, while the underlying mechanisms at the microscopic level remain unclear. In this study, we employed molecular dynamics simulations to investigate the microscale reaction behavior of geopolymers, exploring the induction process and structural evolution during the initial stages, and revealing the similarities and differences under alkali activation for different materials. Our findings indicate that the alkali activation process can be divided into two stages: mineral crystal deconstruction and oligomer polymerization. The role of NaOH differs between low-calcium and high-calcium systems, where in the low-calcium system, Na+ substitutes Ca2+ due to Ca2+ deficiency, participating in the formation of the network framework. Moreover, the high-calcium system exhibits a faster formation of the gel phase during alkali activation compared to the low-calcium system. This study provides valuable insights into the research and application of geopolymers.

The Military and Civilian Applications of Geopolymers

In this article, various geopolymer applications in the context of both existing and potential future military applications are summarized. Geopolymers are a type of alkaline activated concrete binder with many advantageous properties over ordinary Portland cement based materials. Geopolymers are first compared to ordinary Portland cement based materials in regards to their mechanical properties, thermal properties, chemical resistance and CO2 emissions during manufacturing. History of geopolymer applications and research is also discussed. Then, various geopolymer applications are summarized, including their use as a passive fire protection, material for general construction, “ink”for 3D printing. These types of applications are also discussed in the context of existing and potential military applications of geopolymers, including their use by U.S. armed forces and U.S. military research. Superior geopolymer resistance to explosions is also presented.

An Application of Geopolymer stabilized expansive soil to reduce the rainfall-based erosion in slopes

Soil stabilization is critical in civil infrastructure, acting as a cornerstone for sustainable and resilient building practices. It enables the construction of strong foundations capable of withstanding enormous loads and adverse conditions, assuring the safety and lifespan of structures such as buildings and roads. The utilization of industrial by products for enhancing the qualities of locally expanding soils has become increasingly popular, mostly due to its low carbon emissions and cost-effectiveness. The present investigation focused on the effect of the addition of Ground Granulated Blast furnace Slag (GGBS) and Geopolymer solution to expansive soil in order to reduce the erosion of slopes. Unconfined compressive strength tests were performed and found that 10% GGBS is the optimum amount for stabilization. SEM studies were conducted to know the microstructure before and after stabilization. The study determined that the rate of rainfall erosion on the stabilized slope was lower compared to the untreated soil, and the load-carrying capacity of the stabilized slope was much greater.

Geopolymers: Advanced Materials in Medicine, Energy, Anticorrosion and Environmental Protection

The initial predictions of the importance of geopolymers primarily assumed use mainly in the construction sector. However, as research progresses, it is becoming clear that these versatile materials demonstrate the ability to greatly exceed their original applications, as characterized in detail in this review article. To the best of our knowledge, there is no literature review concerning geopolymer materials that compiles the diverse applications of these versatile materials. This paper focuses on geopolymer applications beyond the construction industry. The surprising application potential of geopolymers in medicine has become a topic of particular interest. Therefore, considerable attention in this paper is devoted to characterizing the utility of these materials in tissue engineering, dentistry and drug delivery systems. Geopolymers not only have exceptional heat resistance and compressive strength, making them durable and resistant to manipulation (over five times less drug released from the geopolymer carrier compared to the commercial formulation), but also provide a robust solution for extended-release drug delivery systems, especially in opioid formulations. Their chemical stability, porous structure and ability to maintain structure after repeated regeneration processes speak to their potential in water treatment. Geopolymers, which excel in the energy industry as refractory materials due to their resistance to high temperatures and refractory properties, also present potential in thermal insulation and energy storage. It was demonstrated that geopolymer-based systems may even be 35% cheaper than conventional ones and show 70% lower thermal conductivity. In terms of protection against microorganisms, the possibility of modifying geopolymers with antimicrobial additives shows their adaptability, maintaining their effectiveness even under high-temperature conditions. Research into their use as anticorrosion materials is targeting corrosion-resistant coatings, with geopolymers containing graphene oxide showing particularly promising results. The multitude of potential applications for geopolymers in a variety of fields reflects their enormous potential. As research progresses, the scope of their possibilities continues to expand, offering innovative solutions to pressing global challenges.

Mechanisms of Zn removal from water by amorphous geopolymer: Molecular-level insights from X-ray absorption spectroscopy, isotope fractionation, and surface complexation modeling

Porous geopolymers have attracted widespread attention as promising heavy metal adsorbents that can be synthesized from aluminosilicate solid wastes. However, the precise microstructural evidence for adsorbed heavy metals on geopolymers remains unclear due to the insensitivity of conventional characterization techniques on minerals with amorphous structure and surface disorder. Batch adsorption and column experiments coupled with X-ray absorption spectroscopy (XAS), Zn stable isotope, and surface complexation model (SCM) were employed to reveal the Zn removal mechanisms with coal fly ash porous geopolymer (CFAPG) at a molecular scale. The macroscopic kinetic and isothermal adsorption of Zn on CFAPG were well described by the pseudo-second-order model and Bi_Langmuir equation, respectively, indicating the presence of abundant heterogeneous active sites on the CFAPG surface. Two types of active sites on the CFAPG surface were identified by XAS coupled with Zn isotopes in batch experiments at pH ≤ 6.0: one is pH-dependent and associated with tetrahedral zinc coordination, and the other is pH-insensitive and associated with octahedral zinc coordination; these sites were confirmed by the bidentate SCM as the variable charge site (surface complexation, >S-OH) and the permanent negative charge site (cation exchange, >X–), respectively. Furthermore, the important contribution of surface co-precipitation besides surface complexation and cation exchange to the Zn adsorption on CFAPG was identified by XAS coupled with SCM in a flow-through column experiment at pH >6.0. These investigations provide a systemic understanding of the Zn adsorption mechanisms on CFAPG and an SCM reference for the application and prediction of geopolymers in heavy metal-contaminated water remediations.

A numerical study of geopolymer concrete thermal energy storage: Benchmarking TES module design and optimizing thermal performance

Geopolymer (GEO) concrete emerges as a potential high-temperature thermal energy storage (TES) material, offering a remarkable thermal storage capacity, approximately 3.5 times higher than regular Portland cement (OPC) concrete, without compromising its environmentally benign nature.This research dissects the application of GEO concrete as a high-temperature TES material, primarily focusing on its optimization and scalability. The introductory part of the study involves the development and validation of a three-dimensional numerical model using computational fluid dynamics (CFD). The model demonstrated an average accuracy rate of 5 %, as justified by empirical data. Later, a two-tiered investigation to determine the optimal design for GEO concrete TES systems was investigated. Three different geometries plus the impact of crucial parameters such as air velocity, tube diameter, and module size on the thermal storage capacity (Q) studied. It further extends into a parametric examination, exploring a variety of tube sizes, arrangements, and configurations. It is found that air velocity primarily influences Q.A subsequent phase provides an analysis of the thermodynamic effects brought by the inclusion of tubes within TES modules through an equivalent parametric study. It exposes the thermal resistance resulting from tube insertion. The study reinforces the superior thermal performance of tubeless GEO concrete TES configurations, as signified by overall heat transfer rate (Q̇). The study also signals the significant roles of key parameters in determining the temperature (T) and Q within TES unit using Pearson's correlation coefficient equation.As a final observation, this work emphasizes the sustained significance of on-site evaluations to consistently monitor the interplay between TES materials and high-temperature fluids (HTFs) over extended periods for viability analysis purposes.

Performance and applications of lightweight geopolymer and alkali activated composites with incorporation of ceramic, polymeric and lignocellulosic wastes as aggregates: A review

As the construction industry moves towards greater sustainability, the application of more durable and environmentally friendly materials, capable of providing comfort in buildings and infrastructure, is a key element to consider. In this context, the use of alkali-activated binders (AAB) and geopolymers (GP), which have a lower carbon footprint than ordinary Portland cement (OPC), has emerged as an important alternative. Moreover, the addition of waste-based lightweight aggregates (LWA) to AAB and GP matrices produces lightweight composites that offer enhanced mechanical performance and improved comfort as building materials, while offering an alternative use to the increasing number of waste materials from diverse sources. This paper presents a comprehensive review of the literature on the above-mentioned topics (waste LWA in an AAB/GP matrix) published between 2012 and 2023, mainly indexed in the Scopus database. The waste-based LWA reported in the literature were categorized, and their properties and morphology presented. Then, the influence of the size, quantity, and nature of the LWA on the composite's properties and performance was analyzed. Fresh state performance, mechanical performance, density, and thermal and acoustic insulation were considered. This review is complemented by a bibliometric analysis, where keyword correlation and co-authorship networks on this field are established. The review highlights the potential of cementitious composites including waste-based LWA as a sustainable building material for structural and non-structural applications. However, more studies are required to further understand the behaviour of these composites under innovative manufacturing processes, such as extrusion and 3D printing.

Maximizing the pozzolanic potential of superfine iron tailings for low-carbon stabilization: Application of high-calcium geopolymer

Superfine iron tailings (5–75 μm) are difficult to be reused with traditional binders. The reaction behavior of newly developed high-calcium geopolymer (ASF), the activation effect of the ASF on the pozzolanic potential of tailings, and the application effectiveness of the ASF-stabilized mixtures have been discussed. The results show that highly cross-linked calcium aluminosilicate hydrates were the main hydration products, and there were some crystal products, e.g., stratlingite, ettringite, and crystalline calcium silicate hydrate. The ASF can activate and release magnesium ions in superfine tailings to form magnesium-based products. Second, the cumulative pore volume of stabilized tailings was reduced by 24.4% with the dosage increase of ASF binder from 3% to 8%. Finally, the strength of 8% ASF-stabilized tailings increased from 1.83 MPa to 3.44 MPa (7 d to 28 d). The alkalinity of ASF-stabilized tailings was weaker than that of the cement-based counterpart (∼0.6), reducing environmental pressure during application.

Application of CO2-loaded geopolymer in Zn removal from water: A multi-win strategy for coal fly ash disposal, CO2 emission reduction, and heavy metal-contaminated water treatment

Coal fly ash accumulation, global warming, and heavy metal-contaminated water environments are three primary environmental concerns. Porous geopolymers are economical porous adsorbents that can be produced using coal fly ash as a raw material and employed for heavy metal removal from water. However, residual alkalis on the geopolymer can lead to extreme increases in pH and cause environmental stresses, which limits the large-scale production and application of geopolymers in industries and environments. A green approach to alleviating the high basicity of geopolymers through CO2 exposure is proposed, with CO2 adsorption experiments as well as Zn removal batch and column experiments conducted to evaluate the practicality of the synergistic strategy. CO2 adsorption experiments show the CO2 capture capacity of fresh geopolymer (F@PG) is 0.80 mmol g−1, greater than that of the conventionally washed geopolymer (W@PG, 0.26 mmol g−1), with the pH of the geopolymer decreasing after both washing and CO2 exposure. Batch experiments suggest neither washing nor CO2 exposure cause a significant change in the Zn adsorption capacity of the geopolymer; column experiments show the CO2-exposed geopolymer (C@PG) has a pH < 9.5 and a satisfactory Zn removal performance similar to W@PG, but F@PG with a pH ∼12 results in a conversion of Zn to anionic forms and a decrease in Zn removal efficiency. These results indicate CO2 exposure is a practical method to decrease the pH of geopolymers for applications related to heavy metal-contaminated water treatment and provide a large-scale industrial option for coal fly ash consumption and CO2 emission reduction.

SINTESIS GEOPOLIMER DENGAN BAHAN DASAR KAOLIN CAPKALA SEBAGAI ADSORBEN ION Pb(II) DALAM LARUTAN (SYNTHESIS OF GEOPOLYMERS WITH BASE MATERIALS KAOLIN CAPKALA AS ADSORBENT ION Pb(II) IN SOLUTION)

Geopolymer synthesis was carried out using kaolin, for the adsorption of Pb (II) ions in solutions. Kaolin is used by Kaolin Capkala from Bengkayang Regency, West Kalimantan. This kaolin was first modified into metakaolin. The scaling up of geopolymers is carried out by making an activating solution, namely by mixing NaOH and Na2SiO3. The activating solution is mixed into metakaolin. The mass composition of each component in the geopolymer: metakaolin of 94,5 grams, Na2SiO3 of 57 grams, NaOH of 12 grams, and H2O of 30 grams. The formed geopolymers are tested for their adsorption ability against Pb(II) ions. The research results show the success of geopolymer formation as indicated by FTIR and XRD characterization results. Based on the FTIR results, several indications of successful geopolymer formation are seen in the shift and widening of the Si-O absorption peak at wave number 1109 cm-1 for kaolin to 1058 cm-1 for metakaolin and 1016 cm-1 for geopolymer; the appearance of O-C-O bond absorption in CO32- at 1362 cm-1 in geopolymer; and a shift in absorption of Al-O (Al (VI), wherein kaolin it is indicated by a wave number of 536 cm-1 while in metakaolin it is characterized by a wave number of 544 cm-1 and for geopolymer a wave number of 553 cm-1 indicates it. XRD diffractogram of the formation hump's appearance shows the amorphous characteristics of metakaolin and geopolymer at around 2θ 26o-35o. The application of geopolymer for Pb adsorption shows that Pb(II) can be adsorbed well in geopolymers with the maximum adsorption capacity of 2.77 mg/ g obtained at various concentrations of 40 ppm.

Influence of interface inclination angle and load impact velocity on dynamic splitting tensile behavior and dissipated energy of geopolymer-concrete composites

The application of geopolymer has great potential in repairing damaged concrete. In engineering construction, the repaired structure is often affected by dynamic loading. Experimental research on the dynamic mechanical behavior and energy dissipation of geopolymer-concrete composites (GCC) is of great significance for understanding the bonding performance between geopolymer and concrete. In this paper, dynamic splitting experiment was performed on GCC under different interface inclination angles and load impact velocities by using the split Hopkinson pressure bar (SHPB). Then, the influence of interface inclination angle and load impact velocity on dynamic splitting tensile behavior and dissipated energy of GCC were discussed. Finally, the failure modes and strain field were analyzed based on digital image correlation (DIC) technique. The results indicate that the static peak load of GCC is roughly distributed around 26.0 kN and the dynamic peak load is 263.0 kN. The dynamic peak load measured by GCC is more than 10 times the static peak load. As the interface inclination angle increases from 0° to 90°, the dynamic peak load, static peak load and energy dissipation rate increase linearly, while the tensile sensitivity coefficient decreases. The energy dissipation ratio of GCC is kept between 0.30 and 0.40. In addition, the dynamic peak load, tensile sensitivity coefficient and dissipated energy increase gradually as the load impact velocity increases. A transition from interface failure to tensile failure can be found in GCC with the inclination angle increases.

On the use of one-part geopolymer activated by solid sodium silicate in soft clay stabilization

The application of geopolymers in ground improvement has garnered significant attention in recent years. However, most geopolymer preparations have focused on the two-part method, which not only has negative environmental impacts but also falls short of meeting practical requirements. This study aimed to address these limitations by employing solid sodium silicate (Na2O·nSiO2, n is the molar ratio, NS) to activate binary precursors (fly ash [FA] and ground granulated blast furnace slag [GGBFS]), along with water, to synthesize a one-part geopolymer (OPG) for soft clay stabilization. The primary factors on the properties of the OPG binder were firstly identified through macro- and micro-tests. Subsequently, the optimization of the OPG mixing proportion was achieved by reducing the molar concentration of NS, and was further used for soft clay stabilization. The effects of the FA/GGBFS ratio (0, 0.1, and 0.2), curing period (7, 14, and 28 days), and binder content (0.15, 0.20, and 0.25) on the mechanical properties of the OPG-stabilized soft clay were then evaluated using unconfined compressive strength (UCS) tests. Furthermore, mercury intrusion porosimetry (MIP), scanning electron microscopy with energy dispersive X-ray spectrometry (SEM-EDS), and X-ray diffraction (XRD) techniques were employed to examine the evolution of microstructure, hydrate composition, and mineral/phase of the OPG-stabilized soft clay samples. The experimental results indicated that an appropriate OPG stabilizer proportion was achieved with an FA/GGBFS ratio of 0.1, water/precursor ratio of 0.8, molar ratio of NS of 1.0, and molar concentration of 3 mol/L. The high-early-strength feature of OPG binder contributed to the rapid strength development of the stabilized soft clay at an early age. A noticeable pozzolanic reaction was observed in the OPG-stabilized soft clay sample with an FA/GGBFS ratio of 0.1. Additionally, a binder content of 0.20 was recommended for the stabilization of soft clay due to its optimal balance between economic benefits and meeting the required UCS criteria in soil stabilization. Finally, a reliable nonlinear relationship between UCS and porosity of OPG-stabilized soft clay was established to assess the mechanical properties and stabilization effects of the OPG-stabilized soft clay for practical applications. This study greatly enhances the scientific understanding of geopolymerization in the OPG system by using a combination of the binary precursor of FA and GGBFS and the solid NS activator. It sheds light on the stabilization mechanism of OPG-stabilized soft clay. The outcomes of this study make a valuable contribution to the advancement of environmentally friendly soil stabilizers, promoting green and low-carbon practices in the field of ground improvement.

Geopolymer Antimicrobial and Hydrophobic Modifications: A Review

The article summarizes the state of the art in increasing antimicrobial activity and hydrophobic properties of geopolymer materials. Geopolymers are inorganic polymers formed by polycondensation of aluminosilicate precursors in an alkaline environment and are considered a viable alternative to ordinary Portland cement-based materials, due to their improved mechanical properties, resistance to chemicals, resistance to high temperature, and lower carbon footprint. Like concrete, they are susceptible to microbially induced deterioration (corrosion), especially in a humid environment, primarily due to surface colonization by sulphur-oxidizing bacteria. This paper reviews various methods for hydrophobic or antimicrobial protection by the method of critical analysis of the literature and the results are discussed, along with potential applications of geopolymers with improved antimicrobial properties. Metal nanoparticles, despite their risks, along with PDMS and epoxy coatings, are the most investigated and effective materials for geopolymer protection. Additionally, future prospects, risks, and challenges for geopolymer research and protection against degradation are presented and discussed.

Experimental study on mechanical properties of coal gangue base geopolymer recycled aggregate concrete reinforced by steel fiber and nano-Al2O3

Abstract Using recycled aggregates to prepare geopolymer concrete plays an essential role in reducing dependence on natural resources and solving the problem of waste accumulation. However, the application of geopolymer recycled aggregate concrete (GRC) has been greatly limited due to the defects in the quality of recycled aggregates and the limitations of the brittleness of concrete materials. Therefore, the work is dedicated to improving GRC properties and exploring the mechanism of action of steel fiber (SF) and nano-Al2O3. In this study, calcined gangue, slag, fly ash, and recycled aggregate were used as raw materials, the influence of SFs (0–1.25 vol%) was first explored by single factor analysis, and on this basis, the effect of nano-Al2O3 (NA) (0–2 wt%) on the GPC performance of SF was studied. The microstructure of GRC was analyzed by scanning electron microscopy. The test results showed that adding SF could significantly improve the splitting tensile and flexural strength of GRC, among which 0.75 vol% is the most excellent. However, the increase in compressive strength could be more apparent. The addition of NA can make up for the lack of SF in improving compressive performance. When NA content is 1 wt%, the version of GRC is most apparent. Adding 1% NA has the most significant advance in GRC performance. The microstructure analysis showed that the NA could promote the polymerization reaction, generate more gel, and make the contact interface between SF and matrix more compact, thus improving the strength of GRC.

Characterisation and Performance of Nigerian Kaolin and Metakaolin in Geopolymer Synthesis

This study is aimed at characterising and understanding the mechanical and microstructural behaviour of natural and calcined kaolin clay for geopolymer applications. The clay samples obtained from Kaduna State, Northern area of Nigeria, were calcined within the temperature range of 700 and 900oC and are represented by MK7, MK8 and MK9. The raw kaolin and metakaolin were characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF) and scanning electron microscopy (SEM). To produce geopolymer binders, the precursors were reacted with a 1:1 combination of sodium hydroxide and sodium silicate solution and a precursor to activator ratio of 1.2 was suitable for preparation. The compressive strength of the samples was determined at three testing age of 7, 14 and 28 days. From the results obtained, the kaolin-based geopolymer generally had a long setting time and testing was impossible at the 7-day testing age. The compressive strength of other samples however, increased with increase in the calcination temperature. The values obtained at the maximum testing age of 28 days for all samples fall between 5.1 -14.9 MPa. The scanning electron microscope morphology of the produced binder, show the presence of air trapped in the paste which may have reduced the strength value. Vibrating samples before setting can improve the performance of the geopolymer binders by removing most of the trapped air. Geopolymers produced from this study based on strength obtained, can be used in less critical areas of the construction industry.&#x0D;

Scientometric Analysis of Global Research on the Utilization of Geopolymer Composites in Construction Applications

This study conducts a scientometric review on the use of geopolymer mortar and composites in different construction applications. It aims to analyze the findings of past research and reveal the research constituents, development trends, and knowledge gaps. The Scopus database was employed to retrieve the relevant publications, while Bibliometrix was used to conduct the statistical analyses. Results revealed a steady and gradual increase in the number of publications after 2013, as the annual growth rate increased from 23.9% to 45.2% between the timeframes 2003–2013 and 2014–2022, respectively. The analysis highlighted that many authors collaborated on different construction applications of geopolymers regardless of geographic location. Meanwhile, Construction and Building Materials, China, and Universiti Malaysia Perlis were found to be the predominant journal, country, and institution, respectively. The scientometric analysis showed that the most frequently investigated applications for geopolymer mortars and composites were fire resistance, corrosion protection, and repair. Research gaps highlighted that other applications are not as well investigated despite the promising performance of the geopolymer composites, including 3D printing, heavy metals absorption, environmental protection, and underwater applications. Future research is required to assess the use of other alumina and silica-rich binders in geopolymers while also exploring their lifecycle assessment and economic impact.

Mechanical properties and durability of fiber reinforced geopolymer composites: A review on recent progress

AbstractGeopolymer concrete has similar mechanical properties to ordinary Portland cement (OPC) concrete, and even better properties in high temperature, high corrosion environment. However, geopolymer still has the disadvantages of large shrinkage and high brittleness, which greatly limit its application. Fiber reinforcement is widely used in various geopolymer systems to overcome the brittleness issue, but still retains the high strength. Over the past 10 years, great progress has been made in the research of fiber reinforced geopolymers in the aspect of toughening efficiency and durability improvement. Many studies have been conducted on fiber reinforced geopolymers, but there are still few systematic summaries on the addition of inorganic fibers and organic fibers to geopolymers. What is more there are many novel studies such as the application of geopolymers to 3D printing and the new concept of fiber factor have not been reviewed. In this paper, inorganic fibers, natural fibers and synthetic fibers in geopolymers are briefly reviewed, and their specific effects on geopolymers' compressive, flexural, tensile strength, fracture toughness, shear strength and durability such as shrinkage, chemical resistance, freeze–thaw resistance are reviewed. The current understanding of bonding mechanism and fiber‐geopolymer interface are also discussed, and related knowledge gaps and future work challenges are correspondingly pointed out.

The effect of slag and fly ash content on the properties of electric furnace nickel slag-based geopolymer used for repair materials

Large quantities of electric furnace nickel slag (EFNS) are annually generated through the smelting of ferronickel in industries. EFNS contains a large amount of glass phase SiO2 and MgO, with certain volcanic ash activity. Nevertheless, the lower early activity of EFNS due to the ultra-low Ca and Al greatly limits its application. To descend the consumption of raw materials and mitigate environmental pollution, utilizing such wastes as a binding agent in the domain of repairing mortars is a suitable solution. To address the lack of Ca and Al and adjust the ratios of Ca/Al and Si/Al in EFNS-based mortars, the purpose of the research was to incorporate different contents of slag (SL) and fly ash (FA) from 25% to 40%, respectively, into EFNS-based mortars activated with Na2SiO3. The study involved an investigation of the workability, mechanical properties, bond strength, and dry shrinkage of the mortars, employing different percentages of SL and FA. At the same time, TGA, XRD, MIP, and SEM were applied to investigate the chemical composition and microstructure of the binder gel phase. The results showed that when the SL content reached 40% and the FA content was 30%, the repair performance of mortar was much better than numerous repair materials, with an excellent compressive strength (94.0 MPa), flexural strength (11.0 MPa), and bond strength (6.33 MPa). As such, increasing the SL and FA contents seemed to have a positive influence on dry shrinkage and mechanical strengths. Additionally, when the FA content was 30%, the incorporation of SL was found to promote EFNS hydrolysis, and the hydration could directly generate hydrotalcite, which was beneficial to decreasing drying shrinkage at 28 d. The present study provides a theoretical foundation for the application of EFNS-based geopolymers in repair materials.

In-situ grown SiC whiskers enhance flame retardancy of alkali-activated gold tailings geopolymer composite coatings by incorporating expanded graphite

Herein, a gold tailings-based flame-retardant coating blended with zinc phytate (ZnPA)/β-cyclodextrin (β-CD)/expanded graphite (EG) is prepared by the sol-gel method. The coating is used in flame-retardant plywood. It explores the efficient recycling of industrial solid waste. Firstly, the microstructure analysis reveals that EG forms in-situ SiC ceramic whiskers in the solid solution of orthosilicate and pyrophosphate. Meanwhile, the synergistic flame-retardant effect is explained through morphological characterization and pyrolysis kinetics analysis. Adding 2 wt% EG significantly improves the flame retardancy of the coating, as evidenced by a decrease in the peak of heat release rate (p-HRR) and an increase in the fire performance index (FPI). The p-HRR decreases from 104.67 kW·m−2 to 75.08 kW·m−2, while the FPI increases from 2.11 s·m2·kW−1 to 3.51 s·m2·kW−1. Moreover, the pyrolysis kinetics is modeled using the Zhuralev-Lesokin-Tempelman (Z.-L.-T.) three-dimensional diffusion-reaction model, revealing an increase in Eα from 74.90 to 85.82 kJ·mol−1 in the temperature range of 674–890 °C. The coating exhibits 60% formaldehyde adsorption performance. Therefore, this study proposes a new in-situ whisker synergistic flame-retardant system and sheds light on the potential applications of new geopolymers in the sustainable development of the green flame-retardant field.

Comprehensive Evaluation of the Performance and Benefits of SSA-GGBS Geopolymer Mortar.

The activity of sewage sludge ash (SSA) is not high; ground granulated blast slag (GGBS) has a high calcium oxide content that can accelerate polymerization rates and exhibit better mechanical performance. In order to improve the engineering application of SSA-GGBS geopolymer, it is necessary to conduct a comprehensive evaluation of its performance and benefits. In this study, the fresh properties, mechanical performance and benefits of geopolymer mortar with different SSA/GGBS, modulus and Na2O contents were studied. Taking the economic and environmental benefits, working performance and mechanical performance of mortar as evaluation indexes, the entropy weight TOPSIS (Technique for Order Performance by Similarity to Ideal Solution) comprehensive evaluation method is used to evaluate the geopolymer mortar with different proportions. The results show that as SSA/GGBS increases, the workability of mortar decreases, the setting time first increases and then decreases, and the compressive strength and flexural strength decrease. By appropriately increasing the modulus, the workability of the mortar decreases and more silicates are introduced, resulting in increased strength in the later stage. By appropriately increasing the Na2O content, the volcanic ash activity of SSA and GGBS is better stimulated, the polymerization reaction is accelerated, and the early strength increases. The highest Ic (integrated cost index, Ctfc28) of geopolymer mortar is 33.95 CNY/m3/MPa, and the lowest is 16.21 CNY/m3/MPa, which is at least 41.57% higher than that of ordinary Portland cement (OPC). The minimum Ie (embodied CO2 index, Ecfc28) is 6.24 kg/m3/MPa, rising up to 14.15 kg/m3/MPa, which is at least 21.39% lower than that of OPC. The optimal mix ratio is a water-cement ratio of 0.4, a cement-sand ratio of 1.0, SSA/GGBS of 2/8, a modulus content of 1.4, and an Na2O content of 10%.