Slag Geopolymer Research Articles

Exploring the viability of copper slag geopolymer concrete in structural applications: A study on strength variability and seismic risk assessment

This study explores the use of copper slag (CS) as a sustainable alternative to natural sand (NS) in geopolymer concrete (GPC) for structural applications. Despite the potential of CS to promote environmental sustainability by repurposing industrial waste, its adoption in the construction industry remains limited. To address this gap, the study focuses on two main aspects: (i) modelling the uncertainty in the strength properties of CS-based GPC, and (ii) assessing the performance of CS-based GPC in seismic-resistant reinforced concrete (RC) framed buildings. The results show that the compressive strength of CS-based GPC is best represented by the Gumbel max and Gamma distributions, while the splitting tensile strength is well-modelled by Gamma and lognormal distributions. The flexural strength follows Gumbel max and Weibull distributions. These findings provide valuable data for probabilistic structural analysis and reliability-based design. Additionally, the seismic performance of RC frames made with GPC containing CS was found to be comparable to that of control frames with NS, confirming the viability of CS-based GPC in seismic-resistant structures. This research demonstrates that CS can be effectively utilized in GPC without compromising structural safety, contributing to more sustainable concrete construction practices.

Effect of modified multi-walled carbon nanotubes on mechanical properties and microscopic mechanism of lithium slag geopolymers

This study aims to examine the impact of multi-walled carbon nanotubes (MWCNTs) on the mechanical properties and micro-mechanisms of lithium slag geopolymer (LSG), a novel environmentally friendly building material. Two distinct dispersion methods, which used ultrasonication or added sodium dodecyl sulfate (SDS) dispersants, were employed to disperse both pristine and modified MWCNTs. Subsequently, these dispersed MWCNT solutions were mixed with waste lithium slag and stirred to prepare LSG. Based on the experiments, it is concluded that all of these demonstrated the most significant enhancement of LSG mechanical properties at a 0.1 % mass fraction of modified MWCNTs. In comparison with the reference LSG, the compressive and bending strengths of LSG with modified MWCNTs experienced improvements of 23.29 % and 13.76 %, respectively, after a curing period of 28 days. This was also evident from a microscopic perspective. The LSGs doped with modified MWCNTs and SDS exhibited stronger Ai-O-Si and Si-O-Si vibrational bands, as well as broader N-A-S-H and C-S-H characteristic peaks compared to the pristine LSGs. The porosity of LSG samples mixed with a mass fraction of 0.1 % MWCNTs and SDS was 37.08 % lower than that of pristine LSG. FESEM electron micrographs revealed that the modified MWCNTs functioned as fillers, bridges, and extractors of cracks in the hydration products of LSG. The aforementioned results suggest that well-dispersed modified MWCNTs have a beneficial impact on the mechanical properties and microscopic characteristics of LSG.

Alkali-Activated Binders as Sustainable Alternatives to Portland Cement and Their Resistance to Saline Water.

Alkali-activated binders have emerged as promising alternatives to Ordinary Portland Cement (OPC) due to their sustainability features and potential advantages. This study evaluates the durability properties of heat-cured fly ash (FA) and ground granulated blast-furnace slag (GGBFS) geopolymer mortars activated with sodium hydroxide, which were subjected to wet-dry cycling in saline environments. Three series of FA, a FA/GGBFS blend, and GGBFS mortars previously optimized on a compressive strength basis were investigated and compared against two control OPC mixes. Performance indicators such as the water absorption, porosity, flexural strength, and compressive strength were analyzed. The results demonstrate that geopolymer mortars have significantly reduced water absorption and porosity with increasing wet-dry cycles. The compressive strength of the FA/GGBFS mortars also increased from 66.5 MPa (untreated) to 87.9 MPa over 45 cycles. The flexural strength remained stable or improved slightly across all geopolymer mortars. The control OPC specimens experienced significant deterioration, with compressive strength in CEM I 42.5R dropping from 51.8 to 17.1 MPa. These findings highlight the superior durability of geopolymer mortars under harsh saline conditions, demonstrating their potential as a resilient alternative for coastal and marine structures.

Improved carbon fibers dispersion in geopolymer composites

Carbon fibers (CFs) reinforced alkali-activated (AA) ground granulated blast furnace slag (GGBFS) geopolymer composites have excellent mechanical and thermoelectrical properties, as well as low energy consumption and low CO2 emissions during their production. However, the dispersion of CFs in the geopolymer matrix is always a technical issue in the preparation of the green composite material. Therefore, this study comparatively investigated various dispersion methods, including, mixing sequence (pre-mixing and after-mixing methods), dispersing agent (nano silicon dioxide [nSiO2]), and ultrasonic treatment time (0, 15, 30, and 45 min), as well as CFs content (0.5, 1.0, and 1.5 wt% of GGBFS). The distribution of CFs was then qualitatively and quantitatively evaluated by a series of tests, such as flowability, electrical resistivity, flexural strength, scanning electron microscope (SEM) analysis, and X-ray computed tomography (CT). The experimental results showed that the proposed pre-mixing method provided excellent dispersion characteristics for CFs compared with the after-mixing method. The introduction of nSiO2 can enhance the dispersion of CFs and the mechanical and electrical properties of AA GGBFS geopolymer composites. At a carbon fiber content of 1.5 %, the pre-mixing method and the addition of nSiO2 dispersant reduced the resistivity of the 28-day geopolymer composites by 17.0 % and 38 %, respectively, compared with the after-mixing method. It is feasible to use X-ray CT scanning with the gray-scale frequency map to analyze the dispersion effect of CFs in AA GGBFS geopolymer composites. However, the results were not intuitive when less agglomeration of CFs occurred for the low content of CFs. The scanning method is more applicable to the sample with over 1.0 wt% CFs. The average pixel areas of uniformly dispersed CF bundles in the 2D images of the pre-mixing method and the addition of nSiO2 dispersant specimens were 3.32 % and 6.55 % higher than those of the after-mixing method, respectively. The 2D and 3D scanning results from the dispersion characteristics of CFs were consistent. 2D scanning could provide a time-consuming option for the measurement of CFs dispersion characteristics.

Effect of Ca content on the synthesis and properties of FA-GGBFS geopolymer: Combining experiments and molecular dynamics simulation

The elemental components in the precursor of geopolymers are different, and their mechanical properties are also different. As one of the major influencing factors, calcium content is worth further research and exploration. This paper aims to explore the impact of calcium content on fly ash (FA)-ground granulated blast furnace slag (GGBFS) geopolymer in a comprehensive and multi-scale manner through various research methods such as indoor experiments, microscopic experiments, and molecular dynamics simulations. Using GGBFS as the main source of calcium content in geopolymers, different calcium content samples were prepared by adjusting the GGBFS content. The consistency, setting time, compressive strength, flexural strength, elastic modulus, self-shrinkage value, and dry-shrinkage value of the test blocks were tested at corresponding ages. Analyze its microscopic characteristics through scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS). Finally, the structural models of four geopolymer gels with different Ca contents were constructed, and the mechanism of calcium influence was further characterized from the atomic level. The results indicate that an increase in calcium content is beneficial for the rapid hardening of geopolymer mortar, with varying degrees of increase in compressive strength, flexural strength, and elastic modulus. However, with the increase in calcium content, shrinkage is greater, which may lead to durability drawbacks such as cracking in practical engineering. Therefore, the calcium content should be appropriately controlled. The microscopic morphology showed that the polymer became denser with increasing calcium content, and the Ca/Si ratio in EDS also increases accordingly. Molecular dynamics simulation results also show that Ca can form Ca–O bonds with distant oxygen atoms, making the gel structure more stable.

Mechanical properties of bentonite soil stabilized with rice husk ash and ground granulated blast furnace slag geopolymer

Mechanical properties of bentonite soil stabilized with rice husk ash and ground granulated blast furnace slag geopolymer

Use of Metakaolin and Slag Geopolymer Adhesives for Fixing Tiles

Use of Metakaolin and Slag Geopolymer Adhesives for Fixing Tiles

Solidification Mechanism and Strength Characteristics of Alkali-Activated Tannery Sludge–Slag Geopolymer

The aim of this article is to reduce the environmental harm caused by industrial solid waste, specifically tannery sludge, and enable its reutilization. This study prepared an alkali-activated tannery sludge–slag solidification product (ATSSP) with high mechanical properties using blast furnace slag and tannery sludge as raw materials. The response surface methodology (RSM) was used to optimize the product mix ratio. The hydration mechanism and solidification method of ATSSP for Cr in tannery sludge were studied using X-ray diffraction (XRD), scanning electron microscope-energy dispersive spectrometer (SEM-EDS), and Fourier transform infrared reflection (FT-IR). The results indicate that the compressive strength regression model established through RSM has high accuracy and credibility. When the ratio of activator to binder is 0.2174, the alkali activation modulus is 1.02, and the water-to-cement ratio is 0.37; the 28 d compressive strength of ATSSP can reach 71.3 MPa. The sulfate in tannery sludge can promote the secondary hydration reaction of slag, and the generated hydrated calcium silicate and calcite greatly improve the strength of the ATSSP. The reducing substances contained in slag can reduce Cr (VI) in tannery sludge to Cr (III) in the form of uvarovite. The total Cr and Cr (VI) precipitation concentrations of the product are far less than the specification requirements.

Preparation of geopolymers from thermally activated lithium slag: Activity enhancement and microstructure

As an industrial by-product of the lithium extraction process from spodumene, lithium slag (LS) is less reactive, rendering it a chemically infeasible binder. In this study, a thermal activation approach was employed to enhance the reactivity of LS. The underlying mechanisms of LS's thermal activation at various temperatures were thoroughly explored through XRD and ICP. The results indicated that alterations in the aluminosilicate composition of LS occurred during calcination between 500 °C and 900 °C, leading to the transformation of spodumene into amorphous forms. Particularly noteworthy was the initial increase in the LS amorphous phase content with increasing temperature, followed by a subsequent decline. Building upon these findings, a lithium slag geopolymer (LSG) was prepared via alkali activation, using the activated LS as the exclusive precursor. It was observed that elevating the content of active components in LS enhanced the geopolymerization reactions, resulting in an improved mechanical strength of LSG. Remarkably, after 28 days of aging, geopolymer specimens prepared from LS calcined at 700 °C exhibited a compressive strength of 36.0 MPa. Combining these results with FTIR and SEM-EDS analyses, it becomes evident that suitable calcination temperatures empower LS to release a higher quantity of silicon and aluminum ions. These ions play a significant role in the geopolymerization process, leading to the formation of an amorphous sodium (calcium) aluminosilicate hydrate (N(C)-A-S-H) gel. This gel acts as a binder, tightly binding the residual solid particles, and thus forming a denser microstructure.

Thermal stability and strength degradation of lithium slag geopolymer containing fly ash and silica fume

This paper investigates the thermal stability of lithium slag geopolymer (LSG) containing fly ash (FA) and silica fume (SF) exposed up to 900˚C. The effects of elevated temperatures on the microstructural evolution were investigated by thermogravimetric analysis (TGA), X-ray Diffraction (XRD), mineral analysis, surface porosity, and compressive strength of LSG modified by optimum incorporation of fly ash and silica fume. The results indicated that elevated temperature exposure significantly affects compressive strength, surface porosity, void size, weight loss, and phase transformation of fly ash incorporated lithium slag geopolymer (LSGFA) and silica fume incorporated geopolymer (LSGSF). The maximum loss in compressive strength of 44.07% was observed in LSGFA compared to 31.50% loss in LSGSF after exposure at 900˚C. The weight loss of LSGSF was higher than that of LSGFA between 500 and 800˚C and 800–1000˚C indicating a higher degree of dehydroxylation, crystal phase transformation, and viscous sintering observed in the former mix. A larger shrinkage cracking was observed in LSGSF by self-desiccation of the aluminosilicate paste matrix by dehydroxylation of mordenite molecules. Therefore, the degradation of compressive strength is governed by the combination of the crystallization of aluminosilicate gel and the formation of voids.

Synthesis of BiOX-Red Mud/Granulated Blast Furnace Slag Geopolymer Microspheres for Photocatalytic Degradation of Formaldehyde.

Release of formaldehyde gas indoors is a serious threat to human health. The traditional adsorption method is not stable enough for formaldehyde removal. Photocatalytic degradation of formaldehyde is effective and rapid, but photocatalysts are generally expensive and not easy to recycle. In this paper, geopolymer microspheres were applied as matrix materials for photocatalysts loading to degrade formaldehyde. Geopolymer microspheres were prepared from red mud and granulated blast furnace slag as raw materials by alkali activation. When the red mud doping was 50%, the concentration of NaOH solution was 6 mol/L, and the additive amount was 30 mL, the prepared geopolymer microspheres possessed good morphological characteristics and a large specific surface area of 38.80 m2/g. With the loading of BiOX (X = Cl, Br, I) photocatalysts on the surface of geopolymer microspheres, 85.71% of formaldehyde gas were adsorbed within 60 min. The formaldehyde degradation rate of the geopolymer microspheres loaded with BiOI reached 87.46% within 180 min, which was 23.07% higher than that of the microspheres loaded with BiOBr, and 50.50% higher than that of the microspheres loaded with BiOCl. While ensuring the efficient degradation of formaldehyde, the BiOX (X = Cl, Br, I)-loaded geopolymer microspheres are easy to recycle and can save space. This work not only promotes the resource utilization of red mud and granulated blast furnace slag, but also provides a new idea on the formation of catalysts in the process of photocatalytic degradation of formaldehyde.

Micro-assessment of heavy metal immobilization within alkali-activated copper tailings-slag geopolymer

To address the challenge of mitigating heavy metal pollution stemming from the utilization of industrial solid wastes like copper tailings, this study focused on the development of copper tailings-granulated blast furnace slag (CT-GBFS) geopolymer through alkali activation. The primary objective was to effectively immobilize heavy metals, specifically copper (Cu) and zinc (Zn), within the geopolymer. This investigation encompassed an exploration of how Cu and Zn impacted the mechanical properties of CT-GBFS geopolymer, along with an analysis of the leaching behavior of these heavy metals in various environmental conditions. The study also delved into the underlying mechanisms responsible for immobilizing these heavy metals. The experimental findings revealed that the inclusion of up to 2% heavy metals could enhance the mechanical properties of geopolymer. However, as the heavy metal content increased, a detrimental effect on the mechanical properties became evident. Furthermore, CT-GBFS geopolymer exhibited excellent heavy metal immobilization capabilities across different environmental conditions. Specifically, the immobilization rate for copper exceeded 98%, while zinc exhibited an immobilization rate exceeding 93%. The geopolymer has a physical encapsulation fixation mechanism for both Cu and Zn. Additionally, copper was observed to form a covalent bond with non-bridging oxygen in the geopolymer, manifesting as a Si–O–Cu structure, thereby effectively immobilizing the metal. Conversely, zinc was immobilized within the geopolymer through ionic bonding. In conclusion, the technology proposed in this study represents a significant step toward achieving the safe and resourceful utilization of copper tailings by effectively immobilizing heavy metals, thus mitigating their environmental impact.

Strength and microstructural analysis of geopolymer prepared with coal-based synthetic natural gas slag

PurposeThe coal-based synthetic natural gas slag (CSNGS) is a solid waste remaining from the incomplete combustion of raw coal to produce gas. With the continuous promotion of efficient and clean utilization of coal in recent years, the stockpiling of CSNGS would increase gradually, and it would have significant social and environmental benefits with reasonable utilization of CSNGS. This study prepared a new geopolymer by mixing CSNGS with PC42.5 cement in a certain mass ratio as the precursor, with sodium hydroxide and sodium silicate solution as the alkali activators.Design/methodology/approachThe formulation of coal-based synthetic natural gas slag geopolymer (CSNGSG) was determined by an orthogonal test, and then the strength mechanism and microstructure of CSNGSG were characterized by multi-scale tests.FindingsThe results show that the optimum ratio of CSNGSG was a sodium silicate modulus of 1.3, an alkali dosage of 21% and a water cement ratio of 0.36 and the maximum unconfined compressive strength of CSNGSG at 7 d was 26.88 MPa. The increase of curing temperature could significantly improve the compressive strength of CSNGSG, and the curing humidity had little effect on the compressive strength of CSNGSG. The development of the internal strength of CSNSG at high temperatures consumed SiO2, Al2O3 and CaO and the intensity of corresponding crystalline peaks decreased.Originality/valueMoreover, the vibration of chemical bonds in different wavenumbers also revealed the reaction mechanism of CSNSG from another perspective. Finally, the relevant test results indicated that CSNGS had practical application value as a raw material for the preparation of geopolymer cementing materials.

Corrosive effect of HCl and H2SO4 exposure on the strength and microstructure of lithium slag geopolymer mortars

Resistance of geopolymer against aggressive effects of strong acid governs its service life. This research investigates the effect of silica fume incorporation on the strength degradation of lithium slag geopolymer (LSG) mortars after exposure to strong acids and presents the relationship between microstructure, calorimetry, and residual strength. Silica fume incorporated LSG mortars containing sodium (Na) and potassium (K) based alkaline activators were exposed to 5% sulphuric and hydrochloric acid solutions separately for 60 days. The sulphuric acid deterioration of LSG in terms of maximum percentage reduction in compressive strength was 37.42% upon incorporating 40% silica fume in geopolymer with a Na-based alkaline activator. LSG mixes activated by Na-activators demonstrated higher acid resistance compared to those activated by K-based activators. Leaching of aluminium (Al) from the aluminosilicate gel matrix occurred, which subsequently deteriorated aluminosilicate gel matrix when exposed to hydrochloric acid, whereas the leaching of Al occurs alongside the crystallization of calcium sulfate when specimens were exposed to sulphuric acid solution. The incorporation of silica fume reduces the initial calorimetric heat evolution and higher degree of geopolymerization marked by higher heat evolution between 5–48 h than the control LSG. The intense evolution of heat in control LSG at the initial stage of geopolymerization yielded a poor microstructure. Thus, acid-induced strength degradation is lower in silica fume-incorporated gel due to its denser microstructure and higher quantity of aluminosilicate gel formation. Hence, the incorporation of silica fume significantly improved its acid resistance, thus LSG may have industrial applications concerning acid exposure.

Synthesis and Performance Evaluation of Nano-Calcium Carbonate-Modified Geopolymers Incorporating Fly Ash and Manganese Slag: A Comprehensive Investigative Study

Grounded in the auspicious horizons of geological polymers as alternative replacements for Portland cement and aligned with the national endeavor of constructing an ecological civilization and harnessing solid waste as a resource, this study delves into the integration of nanostructured calcium carbonate (CaCO3) into geological polymers derived from fly ash and manganese slag. Employing a comprehensive methodology involving modalities, such as X-ray diffraction, scanning electron microscopy, and attenuated total reflectance Fourier-transform infrared spectroscopy, the influence of nano-CaCO3 on the compressive strength, pore architecture, and polymerization degree of geological polymers is meticulously unveiled. The outcomes reveal that nano-CaCO3 adeptly infiltrates the intricate microporous architecture of geological polymers, thereby providing a compact and intrinsically reinforcing matrix, ultimately endowing a marked increase in compressive strength. The assimilation of nano-CaCO3 correlates conspicuously with an increase in monomeric calcium concentrations, thereby catalyzing and expediting the formation of polymeric assemblages within the system, which in turn accelerates the progression of geological polymerization. This catalytic effect augments the intricate three-dimensional lattice-like gel structures, consequently orchestrating a substantial amelioration in mechanical attributes. When the dosage of nano-CaCO3 was 3.5%, sodium silicate was 10%, and NaOH was 12%, the integrated performance of fly ash–Mn slag geopolymer was optimal. Specifically, the 28-day compressive strength reached 25.6 MPa, and the compressive strength of the weathering performance test increased by 8.31%. The polymer achieved 96.77% curing of Mn, and it was non-radioactive. Thus, the prepared geopolymers are safe and reliable and support the subsequent development of nanomaterial activators.

Effects of nano-SiO2 additives on carbon fiber-reinforced fly ash–slag geopolymer composites performance: Workability, mechanical properties, and microstructure

Abstract Fly ash and slag are commonly used precursors in alkali-activated concrete. However, they suffer from high brittleness, poor toughness, and susceptibility to cracking. To address these limitations, this experimental study investigates the effects of different contents of nano-silica (SiO2) additives on the workability, mechanical properties, and microstructure of carbon fiber-reinforced fly ash–slag geopolymer composites (CFSGs). The results indicate that owing to its large specific surface area, nano-SiO2 significantly increases the water demand of the geopolymer, thereby considerably decreasing the fluidity and shortening the setting time of the geopolymer. However, nano-SiO2 improves the porosity, water absorption, and mechanical properties of the CFSG. The optimal mechanical strength is obtained by using 2% nano-SiO2. In addition, appropriate nanodoping can relatively improve the bearing capacity and fracture toughness of the specimen. Compared with that of undoped CFSG, the peak load, fracture toughness, unstable fracture toughness, and elastic modulus of the 2%-SiO2-doped CFSG increased by 8.78, 5.0, 9.6, and 9.8%, respectively. The incorporation of nano-SiO2 increases the shrinkage of the geopolymer, with a more significant impact on early shrinkage. Moreover, nano-SiO2 improves the microstructure of the cement matrix and interface through the filling, volcanic ash, and crystal nucleus effects as well as interface regulation. This increases the bonding force between the matrix and carbon fibers (CFs), which results in good bonding between the CFs and geopolymer matrix, accelerated geopolymerization reaction, and denser geopolymer paste, thus improving the mechanical strength of the CFSG.

Farklı Molaritelere Sahip KOH Çözeltisi Kullanılarak Üretilen Cüruf Esaslı Geopolimer Harçlarda Kür Sıcaklığı Etkisinin İncelenmesi

Bu çalışmada, farklı kür sıcaklıklarına ve farklı potasyum hidroksit (KOH) oranlarına sahip yüksek fırın cüruflu (YFC) geopolimer harçların fiziksel ve mekanik özellikleri incelenmiştir. Geopolimer harçların karışımında; YFC, su ve agrega miktarı sabit tutulurken KOH’in molaritesi 5, 10, 15, 20 M olarak belirlenmiştir. Hazırlanan harçlar 40x40x160 mm ebatlarında prizma kalıplara yerleştirilmiş ve 50, 75 ve 100 °C sıcaklıklarda 24 saat küre tabi tutulmuşlardır. Elde edilen numuneler; 1, 7 ve 28 gün laboratuvar koşullarında bekletildikten sonra dayanım değerleri belirlenmiştir. Ayrıca 28 günlük harçların birim ağırlık, su emme, boşluk oranı ve ultrases geçiş hızı gibi fiziksel özellikleri belirlenmiştir.

Investigation of Affecting Factors on Drying Shrinkage and Compressive Strength of Slag Geopolymer Mortar Mixture

Investigation of Affecting Factors on Drying Shrinkage and Compressive Strength of Slag Geopolymer Mortar Mixture

Microstructural and mechanical properties of a high-strength geopolymer based on coal-based synthetic natural gas slag cured at ambient temperature

In this study, an effort was made to enhance the mechanical properties of coal-based synthetic natural gas slag (CSNGS) geopolymer with curing at ambient temperature by incorporating ground granulated blast furnace slag (GBFS). The effects of GBFS content, activator modulus and alkali content on the compressive strength of CSNGS-GBFS (CG) geopolymers were analyzed, and the microstructural characteristics and the compositional evolution of reaction products were also investigated by X-ray diffraction (XRD), scanning electron microscope-energy dispersive spectrometer (SEM/EDS), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analyzer (TG) tests. It was found that the mechanical properties of CG geopolymers was highly dependent on the of GBFS content. When the GBFS content was 50%, the 1-day and 28-day strengths of the geopolymer were 50.8 MPa and 120.2 MPa, respectively. Increasing alkali content resulted in the strength of geopolymer to increase and then decrease, whereas, the strength of geopolymer increased monotonically with a decrease in activator modulus. The results also showed that with increasing the GBFS contents, the characteristic peaks corresponding to the gels in the XRD patterns became gradually obvious with highly denser microstructures formed by a number of gels in the SEM micrographs, and the Ca/Si ratio and Ca/(Si + Al) ratio of the reaction products were increased, revealing that the gels generated in CG geopolymers was a mixture of N-A-S-H and C-(A)-S-H gels, which corroborated with the observed the stretching vibration of Si–O-T (T = Si or Al) in FT-IR spectrum shifted from 1013 cm−1 to 990 cm−1 and the corresponding temperatures of the mass loss peaks increased form 104 °C–114 °C. In addition, the dissolution of raw materials was promoted owing to the reduction of the activator modulus, but the change of activator modulus had little effect on the thermal stability of the gels. These findings suggest that CSNGS has the potential to prepare high-strength geopolymers at ambient temperature, providing an attractive avenue for reducing the environmental impact of CSNGS and conserving natural resources.

A comprehensive micro-nano investigative approach to study the development of aluminosilicate gel in binary blends of lithium slag geopolymer

This study extensively investigates the formation of aluminosilicate gel in binary blends of lithium slag geopolymer (LSG) containing fly ash and silica fume. A comprehensive analysis of the aluminosilicate gel was performed at the micro-nano scale, employing techniques such as mineralogical, crystallographic, micromorphological, and micromechanical analysis. C-(N)-A-S-H and N-(C)-A-S-H gels were found between Si/Al ratios of 2.41–3.04 and 3.88 to 4.33, respectively. Fly ash incorporated LSG at 45% alkaline activator yielded the highest average nano-indented modulus of 22.54 GPa. Statistical Gaussian deconvolution was employed to categorize mineral phases in nano-indentation of LSG, revealing substantial distinctions indicated by the low p-values. Carbonation in silica fume incorporated LSG was affirmed by selected area electron diffraction (SAED) patterns of calcite crystallites. The microstructure of LSG containing fly ash was stiffened by the growth of needle crystals of hydroxy-sodalite and aluminosilicate gel. Thus, the formation of C-(N)-A-S-H gel and hydroxy-sodalite governs the strength development of LSG binary blends.