Geopolymer Research Articles (Page 1)

Abstract The addition of phase change materials (PCM) to geo polymer mortar (GPM) is a promising advance in the pursuit of ecologically benign and energy‐efficient construction materials. This review looks at the synthesis, characterization, and performance of GPMs, with a particular emphasis on the consequences of adding PCMs. The review emphasizes the growing global demand for energy‐efficient construction solutions and discusses the critical role of geo polymer mortar in meeting this demand. It also addresses the synergy between PCM and GPM, revealing the principles underlying PCM's latent heat storage capacities and the geo polymer's ability to operate as a stable and durable matrix. Major findings show that PCMs considerably improve the thermal characteristics of GPMs by increasing heat capacity and decreasing thermal conductivity. In addition to boosting durability and thermal resilience, the energy‐storing PCM and the strong GPM combo increase long‐term performance. The PCM incorporated GPM improves thermal energy storage capacities; energy savings of up to 30% for cooling and 15% for heating. However, the addition of PCMs often results in a minor drop in mechanical performance, particularly compressive strength. Although the mortar is weak due to the development of air spaces and weak connections between the PCM capsules and the mortar matrix the strengths are within acceptable limits. Future study is needed to improve long‐term performance and endurance in demanding real‐world environments. This comprehensive review will inspire further research, innovation, and adoption of this technology, thereby contributing to a greener and more energy‐efficient built environment.

Barium carbonate (BaCO3) nanoparticles were synthesized by a facile hydrolysis route using BaCl2 and KOH in aqueous solution, with atmospheric CO2 as the carbonate source, without external agents. Their structural and morphological properties were investigated by XRD, ATR-FTIR, SEM, and BET, confirming the formation of a pure orthorhombic witherite phase with rod-like morphology and different surface specific areas. The crystallite size increased from 52 to 86 nm with higher precursor concentration and synthesis temperature, as predicted by a regression model correlating synthesis parameter with particle growth. When incorporated into polymer (PVC) and geopolymer (GP) matrices, BaCO3 enhanced the photocatalytic degradation of methylene blue (MB) under solar light, with GP@Nano-BaCO3 achieving a higher rate constant compared to PVC@Nano-BaCO3. The results highlight that the synthesis strategy yields well-defined BaCO3 nanoparticles with tunable structural features and promising photocatalytic potential when integrated in functional polymer matrices. Future work will address doping strategies and testing in real wastewater conditions. Overall, this synthesis strategy offers a reproducible and environmentally friendly route to BaCO3 nanoparticles with potential applications in hybrid materials for visible light-driven environmental remediation.

The delamination of building facades creates a critical demand for inorganic adhesive mortars with high long-term adhesion. Geopolymer (GP) represents an eco-friendly alternative to Portland cement (PC). However, the effect of polymer additives, commonly used in cement-based adhesive mortars, on GP mortar remains insufficiently studied. This study examines the effects of hydroxypropyl methylcellulose (HPMC) and vinyl acetate-ethylene (VAE) polymer on the workability, mechanical properties, durability, and microstructure of GP mortar. Results show that an optimal HPMC content (0.4 wt%) improves the fluidity, compressive strength, and adhesive strength of GP mortar, approximately 6%, 16%, and 20%, respectively. These enhancements are attributed to the incorporation of uniformly distributed microbubbles in the mortar matrix. Beyond this optimal content, however, HPMC impairs flowability and adhesion due to its thickening effect. In contrast, VAE addition significantly enhanced adhesive strength by approximately 28%, albeit at the cost of a 17% reduction in compressive strength, resulting from the retardation of the alkali activation process. This gain in adhesion is associated with the formation of a continuous polymer film that establishes both physical interlocking and chemical bonding with the GP matrix. Furthermore, HPMC improved the durability of the GP mortar, while VAE did not contribute to this aspect. These insights offer valuable guidance for designing high-performance GP-based adhesive mortars suitable for building applications.

This paper assesses the feasibility of metakaolin (MK)-based geopolymer (GP) composite as an environmentally friendly substitute for cement-based composite in repair applications. The Taguchi orthogonal array method was used to find the optimum GP mix in terms of mechanical properties and adhesion to concrete substrates. Four key parameters, each with three levels, are investigated including the alkaline activator-to-MK ratio (A/M: 1, 1.2, 1.4), the sodium silicate-to-sodium hydroxide ratio (S/H: 2.0, 2.5, 3.0), sodium hydroxide (SH) molarity (12, 14, 16), and curing temperature (30, 45, 60 °C). The evaluated properties include flowability, compressive strength, splitting tensile strength, flexural strength, ultrasonic pulse velocity, and bond strength under various interface configurations. Experimental results demonstrated that the performance of MK-based GP composite was primarily governed by the A/M ratio and sodium hydroxide molarity. The Taguchi optimization method revealed that the mix design featuring A/M of 1.4, SS/SH of 2, 16 M sodium hydroxide, and curing at 60 °C yielded notable improvements in compressive and bond strengths compared to conventional cement-based composites.

Memristors are solid-state devices that share many information processing capabilities of biological synapses, allowing brain-inspired memory and computing. Among memristor-based neuromorphic computing systems, physical reservoir computing has gained significant attention in recent years due to its low computational cost and suitability in handling multiple tasks by leveraging the short-term memory property of artificial synapses. In our previous studies, we developed geopolymer (GP)-based low-cost memristors and demonstrated their activity-dependent behaviors, such as short-term plasticity behaviors [including Paired-Pulse Facilitation (PPF) and Paired-Pulse Depression (PPD)] and long-term plasticity behaviors [including spike-timing-dependent plasticity and Spike-Rate-Dependent Plasticity (SRDP)]. GPs are a class of inorganic polymers formed by the alkali activation of aluminosilicate precursors. In this study, we present an efficient and low-cost geopolymer-based reservoir computing system capable of recognizing a computer-generated 5 × 5 binary digit set and a handwritten Modified National Institute of Standards and Technology digit dataset with up to an accuracy of 89%, combining both experimental- and simulation-based approaches. The pattern recognition capability of GP memristors suggests their potential application in integrated energy-efficient and real-time structural health monitoring.

Dark fermentation of cheese whey - supplement materials control the conversion pathways.

Geopolymers offer a sustainable alternative to Portland cement (PC), which significantly contributes to global greenhouse gas emissions. One-part geopolymers (GP), which are synthesized by mixing solid precursors and dry activators with water on-site, present a promising alternative to conventional cement. This study investigates the impact of alkaline activator dosage (6-16%) on the mechanical properties and microstructure of a ternary blended one-part geopolymer cement, incorporating diatomite, feldspar, and ground granulated blast-furnace slag (GGBS) as raw materials. The materials were first evaluated for pozzolanic reactivity through strength activity index, lime saturation, and Frattini tests. Results revealed that activator dosage significantly influenced geopolymer performance. While all mixes exhibited minimal workability, the mechanical properties improved up to an optimal activator dosage. The mix with 10% activator and a sodium silicate (SS) to sodium hydroxide (NH) ratio of 1.5 demonstrated the highest compressive strength (46MPa), split tensile strength (4.69MPa), and flexural strength (7.448MPa) after 28days of curing. Microstructural analysis showed a dense, well-formed structure at the optimum mix, while lower activator dosages led to a less compact structure, and higher dosages caused brittleness and cracking. This study highlights the importance of optimizing activator dosage for enhanced geopolymer performance.

A geopolymer (GP) from Partially Dealuminated Kaolin (PDK) was synthesized. PDK is a solid waste of alum industry, it was produced in a big quantity, which need careful management to be recycled for protection of the environment against pollution. Utilization of PDK is very lacking, and there were no studies for using in the preparation of geopolymer as an adsorbent for heavy metal removal from wastewater. GP was used for the removal of Cr, Cd, and Pb from synthetic industrial wastewater by the adsorption technique. FTIR spectrum indicates a peak at 977 cm−1 due to Si–O–Si and Si–O–Al bonds confirming the formation of geopolymer. The effects of various parameters such as temperature, pH, contact time, and metal ion concentration were tested to stand over the most favorable conditions for adsorption. A total of 100% removal was achieved at a pH = 6.0, temperature = 25 °C, and initial concentration = 40 mg/L for a contact time of 60 min using a dosage of 0.2 g/L. The adsorption data validated Freundlich adsorption model. The values of Freundlich constant value, R2 were greater than 0.99 indicating the adsorption of metal ions onto the geopolymer to be highly favorable. High adsorption capacity has been achieved for Pb, Cd, and Cr (105.6 mg/g for Pb, 150 mg/g for Cd, 125 mg/g for Cr). The adsorption process followed pseudo-1st-order kinetics yielding high correlation coefficient and the adsorbed amount at equilibrium. More than 95% of adsorption was achieved at room temperature supports the effectiveness of metal ions adsorption on the geopolymer. This work helps for the reuse of the industrial waste of alum industry through the synthesis of a geopolymeric adsorbent, which can be applied successfully for removal of the Pb, Cd, and Cr ions from the polluted water.

This research explores the effectiveness of eggshell powder (ESP) and polypropylene (PP) fiber in geopolymer (GP) mortars. It examines how various doses of ESP, ranging from 0% to 25%, and two volumes of PP fibers, at 0.1% and 0.2% (by volume), impact the workability, mechanical and physical characteristics, and microstructure of GP mortars. Assessments were made for workability, apparent porosity, water absorption, and flexural and compressive strengths, along with microstructural evaluations. Using ESP as a substitute for metakaolin (MK) at 15% and 25% (by weight) improved the flexural and compressive strengths by 22.9%, 22.5%, 37.1%, and 50.7%, respectively. Using PP fiber resulted in flexural strength improvements of up to 97%. These findings deepen the understanding of ESP’s potential as a partial replacement for MK in geopolymer mortar, provide insights on material enhancement, and demonstrate superior mechanical and durability properties.

Geopolymers (GPs), as promising alternatives to ordinary Portland cement (OPC)-based concrete, have gained interest in the last 20 years due to their enhanced mechanical properties, durability, and lower environmental impact. Synthesized from industrial by-products such as slag and fly ash, geopolymers offer a sustainable solution to waste management, resource utilization, and carbon dioxide reduction. However, similarly to OPC, geopolymers exhibit brittle behavior, and this characteristic defines a limit for structural applications. To tackle this issue, researchers have focused on the characterization, development, and implementation of fiber-reinforced geopolymers (FRGs), which incorporate various fibers to enhance toughness, ductility, and crack resistance, allowing their use in a wide range of structural applications. Following a general overview of sustainability considerations, this review critically analyzes the structural performance and capability of geopolymers in structural repair applications. Geopolymers demonstrate notable potential in new construction and repair applications. However, challenges such as complex mix designs, the availability of alkaline activators, curing temperatures, fiber matrix compatibility issues, and limited standards are restricting its large-scale adoption. The analysis and consolidation of an extensive dataset would support the viability of geopolymer as a durable and sustainable alternative to what is currently used in the construction industry, especially when fiber reinforcement is effectively integrated.

Microwave curing has proven to be a highly effective method for enhancing the structural integrity, compressive strength, and heavy metal immobilization performance of geopolymer (GP) gels. For fly ash-based GP gels, optimal compressive strength (126.84 MPa) and minimal heavy metal ion leaching (0.01 mg/L) were achieved under microwave irradiation at 100 W for 75 s. Similarly, metakaolin-based GP gels reached peak compressive strength (76.84 MPa) and reduced heavy metal leaching (0.44 mg/L) under 440 W irradiation for 60 s. Microwave energy significantly accelerates geopolymerization by promoting the aggregation of dispersed particles, rapidly forming a dense, block-like matrix. This accelerated densification enhances the mechanical properties of GP gels within minutes. Moreover, the dense matrix structure effectively encapsulates heavy metal ions, minimizing their leaching through a combination of physical encapsulation and chemical bonding. In summary, microwave treatment significantly enhances both mechanical performance and heavy metal immobilization, offering a practical pathway for sustainable applications.

This work reflects both the synthesis and the characterization of a novel catalyst obtained by functionalizing geopolymers through the grafting of an amino group onto their surface. Expanded perlite (PE) was chosen as the primary raw material due to its high availability, low cost, and environmental compatibility. Its favorable structure and reactivity with alkaline agents make it an excellent candidate for geopolymer (GP) formation. Subsequently, 3-aminopropyltrimethoxysilane (APTMS) was grafted onto the GP surface to obtain a modified geopolymer catalyst (GPM). The modification enhanced the geopolymer's functionality, making it efficient, eco-friendly, safe, and reusable. Characterization by XRD, SEM, EDX, and TGA confirmed successful grafting and improved the thermal stability of the resulting GPM catalyst. The catalytic efficacy of this novel catalyst was explored for the first time in the synthesis of substituted 4H-chromene, using a direct, straightforward, and highly efficient one-step procedure within a multicomponent reaction. This reaction combines various aldehydes, malononitrile, and β-diketone in ethanol at ambient temperature. The catalyst enabled excellent yields ranging from 90 to 98% under mild and eco-friendly conditions. The resulting 4H-chromene derivatives were confirmed via melting point, FT-IR, 1H NMR, and 13C NMR analyses. Moreover, the GPM catalyst demonstrated high recyclability, maintaining over 90% of its catalytic activity after five consecutive cycles. To complement the experimental findings, DFT calculations (B3LYP/6-31G(d,p)) were performed, providing insight into the electronic properties, including frontier molecular orbitals and molecular electrostatic potentials. These results highlighted the most reactive molecular regions, supporting the potential of the synthesized chromene derivatives in pharmaceutical applications and drug design. Overall, the study demonstrates the effectiveness, sustainability, and broader applicability of the newly developed heterogeneous GPM catalyst. These findings highlight the potential of geopolymer-based catalysts as sustainable alternatives in green chemistry and showcase their versatility for future applications in synthetic and medicinal chemistry.

This research developed an alkali-activated geopolymer (GP) cement using powdered granite waste (GW), blast furnace slag (BFS), and Zirconium aluminum Layered double hydroxide (Zr–Al–CO3 LDH). The alkali-activation reactions were promoted using NaOH and Na2SiO3 (1:1) as an alkaline activator. The durability of various GP mixes was tested by examining their mechanical properties against firing up to 800 °C and exposure to high doses of gamma rays. Results indicated that incorporating up to 30% granite powder into the GP mixture resulted in faster setting times: initial setting time decreased by 20%, and final setting time decreased by 33%. This improvement is attributed to the acceleration of alkali-activation reactions and the increased stiffness of the paste, which is due to the surplus soluble silicon ions released from the granite powder. Replacing BFS with 10% GW led to an improvement in strength by approximately 4–6%. However, increasing the replacement ratio resulted in a decline in mechanical properties. Enhancing the 80% BFS and 20% granite waste (GW) mixture with 0.5–1% of Zr–Al–CO3 LDH significantly increased compression resistance by 37% and 25% at all stages of the alkali activation process. This enhancement in compression resistance is attributed to the nano-filling effect of Zr–Al–CO3 LDH and its ability to improve the bonding between the BFS and granite particles. Furthermore, BFS (blast furnace slag) reinforced with LDH (layered double hydroxide) showed no loss of strength during durability tests against gamma-ray irradiation at doses up to 1000 kGy. Additionally, it demonstrated thermal stability when fired at temperatures up to 800 °C, in contrast to the GP mix made solely from BFS. This behavior is mainly due to the combined action of granite particles, which serve as energy storage and thermal insulating materials, with the nano-filling and/or absorptivity properties of Zr–Al–CO3 LDH within the GP matrix which reinforces the geopolymer structure to endure the detrimental impacts of these demanding environments.

The demand of concrete is increasing day by day for satisfying the need of development of infrastructure facilities. It is well established fact that the production of OPC not only consumes significant amount of natural resources and energy but also releases substantial quantity of carbon dioxide to the atmosphere. Therefore, it is essential to find alternatives to make the concrete environment friendly. Geo polymer is an inorganic alumino-silicate compound, synthesized from fly ash. The fly ash, one of the source materials for geo polymer binders, is available abundantly in India. Hence it is essential to make the efforts to utilize this by-product in concrete manufacturing. This investigation describes the experimental work conducted by casting 20 geo polymer concrete mixes to evaluate the effect of various parameters affecting the compressive cube size100 mm x 100mm x 100mm, Beam size100mm×150mm×1000strength in order to enhance its overall performance. The test results show that compressive strength increases with increase in the curing time, curing temperature, rest period, concentration of sodium hydroxide solution and decreases with increase in the ratio of water to geopolymer solids by mass & admixture dosage, respectively. The addition of naphthalene based superplasticizer improves the workability of fresh geopolymer concrete. It was further observed that the water content in the geopolymer concrete mix plays significant role in achieving the desired compressive strength. Geopolymer Concretes (GPCs) are a new class of concrete based on an inorganic alumino-silicate possessing the advantages of rapid strength gain, elimination of water curing, good mechanical and durability properties and sustainable alternative to Ordinary Portland Cement (OPC). This paper describes experimental investigation on behaviour of reinforced GPC beams subjected to monotonic static loading. The overall dimensions of the GPC beams. The specimens were produced from a mix incorporating Fly ash and GGBS, which was designed for a compressive strength of 40MPa at 28 days. Key Words: Geopolymer, alumino-silicate

Municipal solid waste incineration fly ash (MSWI FA) is a hazardous waste that must be kept in special landfills due to the high amounts of chlorides, sulfates, and heavy metals. The granulation of MSWI FA could be used as a solidification/stabilization (S/S) of fly ash to immobilize hazardous chemical elements and to reduce dust emissions. In this work for granulation, three different binders were used: calcium aluminate cement (CAC), geopolymer (GEO), and Portland cement (PC). Chemical (XRF), mineral (XRD), granulometric compositions, and leaching of prepared granules are presented in the article. Furthermore, the impact of different binders on bulk density, compressive strength, and granule structure was analyzed. The results show that the granules with CAC binder have the best initial compressive strength (about 10 MPa), but these granules were destroyed after the leaching test or connection with water. The geopolymer as a binder did not provide the required compressive strength and immobilization of harmful elements. Granules with a Portland cement binder have a suitable compressive strength, a slight leaching of chemical elements, and good durability in the alkaline and acidic environment; they are also resistant to freezing and thawing cycles.

This study aims to assess the ammonium (NH4+) removal ability of geopolymer made from laterite. The results showed that the NH4+ adsorption efficiency of laterite-based geopolymer (GL) was 9 times higher than raw laterite (LR). GL demonstrated a rapid increase in NH4+ adsorption efficiency in the first 30 minutes, followed by a 90-minute gradual increase and stabilization. The NH4+ adsorption isotherm of GL well fitted with both Langmuir and Freundlich models with a maximum adsorption capacity of 5.28 mg/g. The adsorbent dosage has influenced the adsorption capacity of GL, with the optimal ratio of adsorbent and solution volume being 10g/L. The SEM morphology structure of LR and GL indicates an increase in the surface area owing to higher regions of rough structures in GL compared to LR, contributing to the increment of NH4+ adsorption capacity. These findings emphasize the potential of ammonium removal of laterite-based geopolymer in an aqueous environment.

The usage of geopolymer-based materials (GPBMs) in concrete structures has been broadly promoted by the current construction sector. GPBMs have an outstanding influence on enhancing concrete mechanical properties. Geopolymers (GPs) also have a potential impact on reducing the carbon dioxide emissions emitted by the current cement production procedure. Therefore, this paper aims to evaluate the impact of some variables that affect green and mechanical properties of fly ash-based geopolymer concretes (FA–GPCs), i.e., different silica fume (SF) contents, alkaline activator solution (AAS) percentages, sodium silicate-to-sodium hydroxide (SS/SH) ratios, sodium hydroxide (NaOH) molarity, and additional water. A slump test was used to evaluate the concrete workability to assess the green properties of the designed fly ash-geopolymer concrete mixes (FA–GPCMs). The 14- and 28-day compressive strengths were used to evaluate the concrete’s mechanical properties. Results indicate that the workability of prepared FA–GPCMs reduced with improving SF content (5% to 30%), SS/SH ratio (1% to 3%), and NaOH molarity (10 M to 16 M), while reducing alkaline activator percentages to 35% resulted in a decrease in the FA–GPCMs’ workability. Also, increasing SF replacement percentages from 5% to 15% in FA–GPCMs resulted in significant 14- and 28-day FA–GP compressive strength enhancements compared to FA–GPCM produced with 0% SF, while SF contents of 20%, 25%, and 30% led to a decline in the 14- and 28-day FA–GPC compressive strength compared to that of G1–SF15%.

This research delves into an in-depth exploration of two distinct approaches to additive manufacturing for creating 3D filters based on sodium geopolymers (GP): direct 3D printing through paste extrusion and reverse 3D printing using sacrificial polymeric templates. The investigation encompasses a comprehensive characterization of GP filters in both their fresh and hardened states. By employing rheology measurements during the fresh state analysis, a clear printability zone for formulations used in direct 3D printing is identified. In both printing methods, an extensive assessment of the structure and porosity of the resultant hardened GP filters is conducted, employing Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM) and 3D X-ray microtomography analyses. This study illuminates the distinct advantages and limitations associated with each manufacturing technique in the context of potential industrial applications of porous filters. Moreover, it underscores the potential for these filters to be further tailored for specific industrial uses through complementary chemical functionalization, thereby paving the way for innovation in the field of advanced filtration and environmental solutions.

The aim of this study was to prepare and assess the effectiveness of a geopolymer doped with multi-walled carbon nanotubes functionalized with carboxyl groups (GEO+MWCNT) for removing lead (Pb(II)) and anthracene (ANT) from rainwater. Characterization of the GEO+MWCNT demonstrated an increased specific surface area and microporosity compared to the pristine geopolymer (GEO). Adsorption experiments revealed that GEO+MWCNT achieved higher removal efficiencies for Pb(II) and ANT compared to GEO alone. The maximum removal rates of lead and anthracene by GEO+MWCNT were 100% and 87.5%, respectively, compared to 71.5% and 76.2% for GEO. For GEO+MWCNT, lead removal was 78.2% in anthracene-containing solutions and 86.7% in anthracene-free rainwater. The optimal removal of Pb(II) occurred at pH 8. The adsorption kinetics followed a pseudo-second-order model, indicating a complex mechanism involving physical adsorption, chemisorption, and electrostatic attraction. These findings suggest that geopolymers, particularly when combined with MWCNT-COOH, have significant application potential for rainwater purification processes.

Effect of cation in sodium/potassium-based geopolymer coatings for the fire protection of steel structures