Sustainable Geopolymer Research Articles

Enhanced mechanical and self-healing properties of rice husk ash-incinerated sugarcane press mud biogeopolymer pastes.

This study examines the use of rice husk ash (RHA) and incinerated sugarcane press mud (ISPM) as precursors in the lime/pozzolan geopolymer system and the effect of the bacterium Lysinibacillus sp. WH on the mechanical properties and microstructures. The RHA-to-ISPM ratio was varied, and the geopolymer pastes were cured at ambient temperature. The results show that an increase of ISPM content up to 5% improves strength and reduces water absorption and voids, while higher ISPM levels beyond 5% degrade the quality of geopolymer paste. An increase in ISPM content reduces setting times due to an increase amount of calcium in the pastes. Notably, the addition of bacteria resulting in a reduction of setting times has been proved for the first time in this work. Moreover, the addition of bacteria can enhance all mechanical properties and introduce self-healing abilities, with microcracks healing within < 20 days of treatment, regardless of mix proportions. Microstructural studies, using a scanning electron microscope (SEM), Fourier Transform Infrared Microscopy (FT-IR), X-ray diffraction (XRD), and Rietveld refinement analysis, reveal that bacteria increase cristobalite, and decrease quartz, thus resulting in strength enhancement of geopolymer pastes. Furthermore, this work is the first to provide evidence that bacteria tend to reduce the efflorescence formation as confirmed by a decrease in gaylussite. These findings pave ways to the production of more sustainable geopolymer systems via upcycling wastes and prolonging service life due to bacterial activity.

Recycling E-waste CRT glass in sustainable geopolymer concrete for radiation shielding applications

Waste cathode ray tube (CRT) glass, enriched with heavy metal of Pb, is classified as hazardous waste and needs to be disposed of harmlessly. This study recycles waste CRT glass as heavy aggregate in sustainable geopolymer concretes (GCs) to enhance its γ-ray shielding performance. It also comprehensively evaluates its macro-performances, microstructure, and environmental and economic impacts. The results demonstrate that the compressive strength of GCs decreases with the dosage of CRT glass. The generation of geopolymer gel is hindered by excessive CRT glass. Besides, the compatibility between CRT glass and the geopolymer matrix is poor. Both factors influence the strength development of CRT glass-incorporated GCs. The compressive strength of GCs with 50 % CRT glass aggregate exceeds 30 MPa, meeting the requirements for building materials. Due to the increase in the density and the introduction of heavy nuclei Pb, the γ-ray shielding performance of GCs is 9 % higher than that of normal concrete. In terms of economic and environmental benefits, this approach realizes the value-added recycling of CRT glass, avoiding the disposal cost of CRT glass. Besides, due to the utilization of sustainable geopolymer as cementitious materials, the carbon footprint of designed CRT glass-enhanced radiation shielding GCs is even 34 % lower than that of normal concrete. This study highlights the advantages of geopolymer and CRT glass in developing sustainable radiation shielding materials for nuclear technology and medicine fields.

Attack of discarded soda-lime glass with sodium aluminate for the manufacturing of sustainable geopolymer components

Attack of discarded soda-lime glass with sodium aluminate for the manufacturing of sustainable geopolymer components

Investigating the influence of various metakaolin combinations with different proportions of pond ash and Alccofine 1203 on ternary blended geopolymer concrete at ambient curing.

This paper explores the use of a ternary blended geopolymer concrete (TBGPC) incorporating metakaolin (MK), pond ash (PA), and Alccofine 1203 (AF). Three combinations of MK (25%, 50%, and 75%) with varying proportions of PA and AF were prepared, validating against M30 grade cement concrete (CC). TBGPC was prepared with an 8 molarity sodium hydroxide, sodium silicate to sodium hydroxide ratio of 2.0, liquid to binder ratio of 0.5, and an ambient curing mode. For CC, a water to cement ratio of 0.42 and water curing mode were adopted. The mechanical properties and durability behavior of TBGPC and CC specimens were evaluated through compressive strength, rapid chloride penetration test, permeability test, sorptivity test, and water absorption test. The M50P35A15 mix demonstrated remarkable compressive strength improvements, showing a 203% increase over the CC mix at 1day and 250% by 3days. This trend continued with a 155% increase at 7days, 68% at 28days, and 52% at 90days, consistently outperforming the CC mix. Additionally, microstructure characteristics of the M50P35A15 mix were analyzed through SEM studies, providing validation for the observed strength development. Notably, M50P35A15 mix demonstrated substantially higher early and later strength gain. This enhancement in strength was attributed to the gradual densification of the microstructure over time and the formation of additional NASH and CASH gel in M50P35A15 mix. At 28days, the M50P35A15 mix exhibited excellent durability characteristics, with a Coulomb value of 1008, permeability of 10mm, sorptivity of 0.45mm/√min × 10-4, and water absorption of 1.07%. This study demonstrates the potential of MK, PA, and AF as viable materials for sustainable geopolymer concrete, offering a low-carbon alternative to traditional cement concrete with superior strength and durability aspects.

Sustainable Geopolymer Concrete for Pavements: Performance Evaluation of Recycled Concrete Aggregates in Fly Ash-Based Mixtures

This study investigates the feasibility of incorporating recycled concrete aggregates (RCA) into fly ash-based geopolymer concrete for sustainable pavement applications. The research evaluates RCA’s physical and mechanical properties compared to virgin coarse aggregates (VCA) and assesses the performance of geopolymer concrete mixtures with up to 40% RCA replacement. Aggregate characterization revealed that RCA exhibited higher water absorption (4.39%), crushing value (20.9%), impact value (28.2%), and abrasion value (26.1%) compared to VCA, yet these values remained within acceptable limits for pavement applications. Geopolymer concrete specimens were tested for compressive strength, water absorption, abrasion resistance, and chloride ion permeability. Results indicated that increasing RCA content led to a gradual decrease in compressive strength, from 40.16 MPa to 33.52 MPa, while water absorption increased from 5.2% to 6.8%. Abrasion resistance declined as RCA content rose, and chloride ion penetrability increased from 1687 to 2196 coulombs. However, mixtures with up to 20% RCA replacement met the strength and durability criteria required for pavement construction. This study demonstrates the potential for utilizing RCA in geopolymer concrete pavements, offering a sustainable solution for waste management and resource conservation in the construction industry.

Comprehensive evaluation of microstructure and mechanical performance of sustainable ambient-cured alkali-activated composites

Cement is one of the building materials that is most frequently utilized in the construction field. However, the cement industry contributes significantly to the production of greenhouse gases. Therefore, many works have focused on improving sustainable construction materials that could contribute to decreasing greenhouse gas emissions. This study aimed to design a sustainable geopolymer mortar (GPM) made of fly ash (FA) and ground-granulated blast furnace slag (GGBS), which would be suitable for repairing damaged concrete structures. The work focused on investigating the effect of GGBS percentage, alkaline activator ratio, and superplasticizer dosage on the compressive strength, setting time, and workability of an ambient-cured GPM. The results of this research indicated that the compressive strength of GPM improved with the increase in GGBS percentage until a certain limit. However, the workability and setting time deteriorated with the increase in GGBS percentage. Increasing the alkaline activator ratio contributed to improving the compressive strength, workability, and setting time of GPM up to specific levels, but then they started to reduce. Superplasticizer dosage contributed to enhancing the compressive strength, workability, and setting time of GPM. This study found that the optimum FA/GGBS-based GPM that may be used in repair applications contains 50% GGBS, 50% FA, and 5% superplasticizer. The silica sand/binder ratio and alkaline activator ratio were 2.75 and 1.0, respectively. The compressive strength at 1 day, setting time, and workability of the optimum mix were about 12.70 MPa, 20 min, and 138.75 mm, respectively. The XRF, XRD, TGA, and SEM analyses were useful tools used to interpret the effects of the alkaline activator ratio on the fresh and mechanical properties of GPM.

Improving the Performance of Soil Using Sustainable Geopolymer

Improving the Performance of Soil Using Sustainable Geopolymer

Compatibility of sustainable geopolymer based on artificial neural network

Compatibility of sustainable geopolymer based on artificial neural network

Geopolymer composites reinforced with silverskin fibers from the coffee industry waste

This paper aims to develop sustainable geopolymer composites reinforced with silverskin fibers derived from coffee industry waste. Geopolymer and geopolymer composites were synthesized from blast furnace slags (BFS) with a solid/liquid (alkaline solution) ratio of 1.4. A sodium metasilicate/sodium hydroxide (Na2SiO3/NaOH) mixture at a mass ratio of 2.5 served as the alkaline activator in the geopolymerization process. The composites were evaluated by incorporating 2%, 3%, and 5% by weight of silverskin fibers, which were used in their natural form (SGCn), after treatment with sodium hydroxide (SGCNaOH), and after treatment with sodium hydroxide followed by a steam explosion process (SGCSE).Characterizations of the geopolymer composites included X-ray fluorescence analysis (XRF) for elemental oxide identification, Fourier transform infrared spectroscopy (FTIR) for functional group detection, and thermogravimetric analysis (TGA) for thermal stability assessment. The influence of fibers on the hardness of the geopolymer materials was evaluated using hardness scale measurements. Morphologies, microstructures, and elemental compositions were analyzed through field emission gun scanning electron microscopy with energy dispersive X-ray spectroscopy (FEG-SEM/EDS).The results demonstrate that the incorporation of silverskin fibers, especially those treated with NaOH and subjected to steam explosion, significantly enhances the thermal stability of geopolymer composites. The 5% NaOH-treated fiber composite exhibited the highest Tmax and Tend, indicating superior thermal stability. Additionally, the 5% SGCNaOH composite showed the highest residual mass, further supporting the enhanced thermal stability of these composites.Unlike other fibers, which showed a decrease in hardness, the addition of SGCSE fibers maintains a relatively high hardness in the geopolymer composites. The 2% SGCSE composite exhibited an average hardness equal to that of the pure geopolymer at 66 Shore D.These findings underscore the potential of using treated silverskin fibers to develop more thermally stable, cost-effective, and sustainable geopolymer materials. By utilizing industrial residues and waste, these advanced materials can be applied in the production of construction and building materials, contributing to both environmental sustainability and economic efficiency.

Waste valorization: Sustainable geopolymer production using recycled glass and fly ash at ambient temperature

This research explores the reutilization of waste glass powder (GP) and class F fly ash (FA) in the development of an advanced geopolymer, focusing on reducing natural resource consumption to serve as a green alternative for conventional concrete material. Investigating mix ratios of GP-to-FA (0-to-1), activated with 2–12 M NaOH, followed by ambient temperature curing, this study mainly assesses strength (compressive, and flexural) and durability at different ages. Mechanical properties concerning reaction kinetics and Al/Si ratio, reveal that GP initially acts as an inert filler with slow reaction kinetics, while significant strength improvement at later ages is attributed to the reaction between GP and FA. Optimal performance is achieved with a geopolymer mixture featuring a GP-to-FA ratio of 1:3 (Al/Si ratio of 0.51) and an 8 M NaOH solution, resulting in the highest compressive strength of 40 MPa and superior durability. Microstructural analysis (SEM-EDS, and 29Si MAS NMR) identifies the reacting product as calcium/sodium aluminate silicate hydrate (C/N-(A)-S-H) gel within the geopolymer matrix. Leaching tests further underscore potential environmental concerns related to excessive alkali leaching, necessitating meticulous mix design management. Embodied energy and carbon footprint assessments confirm the environmental friendliness of the GP-FA-based geopolymer. Overall, this research demonstrates the feasibility of producing effective geopolymers from dry waste at ambient temperature, emphasizing the potential synergy between waste glass recycling and the concrete industry towards sustainable construction practices.

Developing geopolymer concrete using fine recycled concrete powder and recycled aggregates

To develop a sustainable geopolymer concrete (GC), the efficacy of using fine recycled concrete powder (FRCP) and recycled aggregates (RA) as partial replacements for fly ash (FA) and natural aggregates (NA), respectively, was investigated. The compressive strengths of different GCs were measured. The durability performance was assessed by means of capillary suction tests, initial surface absorption tests and acid attack performed at ambient curing. The compressive strength of the GC made with 50% RA (both coarse and fine) and FRCP was found to be comparable to that of GC made with NA. Similarly, the inclusion of FRCP in the GC mixes resulted in a pore-blocking effect, restricting water ingress to the GC through capillary suction and surface absorption, even with the use of 50% coarse RA and 25% fine RA. The results demonstrated that sustainable GC can be developed using appropriate doses of FRCP and RA.

Compressive and tensile strength estimation of sustainable geopolymer concrete using contemporary boosting ensemble techniques

Abstract Geopolymer concrete (GPC) serves as an environmentally conscious alternative to traditional concrete, offering a sustainable solution for construction needs. The ability to make on-site changes is dependent on the concrete’s strength after casting, which must be higher than the target value. To anticipate the concrete’s strength before it is poured is, thus, quite helpful. Three ensemble machine learning (ML) approaches, including gradient boosting, AdaBoost regressor, and extreme gradient boosting, are presented in this work as potential methods for forecasting GPC’s mechanical strength that incorporates corncob ash. To determine which modeling parameters are crucial, sensitivity analysis was employed. When the compressive strength and split-tensile strength of GPC were tested with ensemble ML models, R 2 values of more than 90% were discovered between the predicted and actual results. Statistics and a k-fold analysis based on the error and coefficient of determination were used to verify the developed models. Slag amount, curing age, and fine aggregate quantity were the three mix proportions that had the most impact on GPC’s mechanical strength, as shown in the sensitivity analysis. The results of this study demonstrated that ensemble boosting approaches could reliably estimate GPC mechanical strength. Incorporating such procedures into GPC quality control can yield significant improvements.

Development of sustainable geopolymer with excavation soil powder as precursor: Cementitious properties and thermal-activated modification

One of the focal and challenging issues in the research on sustainable building materials pertains to the recycling of construction excavation soil. This paper developed the sustainable geopolymer containing waste soil powder (WSP) from the construction excavation soil as a precursor. The WSP contains a large number of inert components, while more active components were generated in 600–1200 °C thermoactivated WSP. Substituting WSP for metakaolin (MK) negatively impacts the alkali-activated polymerization reaction of MK-based geopolymer paste, but the geopolymer paste containing thermal-activated WSP has better micro-properties than the geopolymer paste containing un-treated WSP. Mixing WSP raises the drying shrinkage of geopolymer mortar, while the drying shrinkage is reduced with the addition of 600–800 °C thermal-activated WSP. The maximum drying shrinkage of geopolymer mortar with 75 % 800°C-activated WSP is 36.6 % lower than that of plain geopolymer mortar. Substituting WSP for MK causes a reduction in the strength and permeability resistance of geopolymer mortar. At the constant replacement rate of WSP, the geopolymer mortar containing thermal-activated WSP has better strength and permeability resistance than the geopolymer mortar containing un-treated WSP. At 100 % replacement rate of WSP, the sustainable geopolymer mortar made with 1200 °C thermal-activated WSP still has good compressive strength (36.38 MPa). The waste soil-concrete powder (WSPC) also serves as an alternative precursor for sustainable geopolymer materials. Substituting WSPC for 100 % MK in geopolymer is feasible, and the geopolymer made with 800 °C thermal-activated WSPC is much greater than the geopolymer made with un-treated WSPC. Optimizing WSP/WSPC substitution rate and thermal activation temperature can achieve the sustainable geopolymer materials with good performance.

Abrasion Resistance and Microstructural Properties of Sustainable Geopolymer Mortar Produced with Hybrid Blends of GGBFS and Various Earth Materials

Abrasion Resistance and Microstructural Properties of Sustainable Geopolymer Mortar Produced with Hybrid Blends of GGBFS and Various Earth Materials

Feasibility of Using Recycled Materials in Construction Materials

The increasing amount of solid waste has become a significant environmental issue that has garnered significant attention and concern. In an effort to mitigate the adverse effects commonly associated with prominent sectors and simultaneously promote credibility in the energy- and resource-intensive realms of development and construction, significant endeavors have been directed towards competitive areas of strength for the purpose of recycling, with the ultimate goal of utilizing such materials in sustainable development products. The present study provides an overview of the ongoing evaluations pertaining to the utilization of conventional and enhanced solid waste for the production of geo-polymer composites. Great attention is devoted to the implementation of these geo-polymer composites. The primary findings of this study revealed that both ordinary and sophisticated solid waste have the potential to be integrated into geo-polymer composites in various forms, such as precursor, complete, additive, reinforcement fiber, or filler material. The findings indicate that the utilization of such waste may have a negative impact on certain properties of geo-polymer composites. However, this issue can be mitigated through the implementation of an open degree plan and appropriate treatment techniques, which can facilitate the recycling process. In conclusion, a concise discourse is presented to acknowledge the significant need for future research and enhancement in advancing the utilization of solid waste materials in the emerging sustainable geo-polymer industry. This study proposes an improved ecological solution for managing municipal and industrial solid waste by transforming waste materials into environmentally friendly construction materials with consistent properties. Special attention is given to the overall performance of geo-polymer composite products. The primary findings of this study reveal that urban and industrial solid waste can be efficiently incorporated into geo-polymer composites through the use of precursors, aggregates, additives, reinforcing fibers, or filler materials. The results indicate that while the inclusion of waste materials may negatively impact certain properties of geo-polymer composites, a well-designed protocol and effective treatment approach can mitigate these adverse effects and facilitate the recycling process. Finally, a brief dialogue is presented to differentiate the key needs in forthcoming research and development aimed at enhancing the utilization of solid waste materials in the upcoming sustainable geopolymer sector. This study provides guidance for the sustainable management of urban waste by transforming waste materials into environmentally friendly construction materials.

Assessment of thermal and mechanical properties of fly ash based geopolymer blocks with a sustainability perspective using multi-criteria decision-making approach

Owing to the raising consciousness about the environment, geopolymers are slowly gaining the trust of researchers globally as the potential alternatives for the conventional building materials. Though, geopolymer emit far less CO2 than conventional building materials, the distance between the source and production site for a particular raw material can have significant impact on the environment. Thus, apart from meeting the mechanical and physical requirement of a building material, it must satisfy the sustainability requirement as well. Therefore, a combination of experimental and analytical method is adopted to select the optimal design mix to produce sustainable geopolymer block which fulfills the performance requirements as well. While compressive and flexural strength test were performed on the geopolymer block made using fly ash (FA) as the primary precursor and glass powder (GP) and steel slag (SS) as the partial replacement to ascertain its mechanical performance, physical performance was assessed by conducting tests like water absorption, bulk density, and thermal conductivity. The sustainability of geopolymer block is assessed by computing sustainability index based on embodied energy, global warming potential and global temperature potential. Multi-criteria decision making (MCDM) approach is then used to select the most optimal mix for geopolymer block production based on the mechanical, physical and sustainability index of each mix for geopolymer. A combination of FA-SS prepared with 14 M NaOH was found to be most sustainable based on the MDCM approach.

Impact of Alkaline Concentration on the Mechanical Properties of Geopolymer Concrete Made up of Fly Ash and Sugarcane Bagasse Ash

Geopolymer concrete (GPC) is a novel and environmentally friendly type of concrete that eliminates the use of cement, resulting in a significant reduction in carbon emissions and a more sustainable construction material. Alkaline activators are used in GPC to achieve rapid strength development. The most popular alkaline activators are sodium/potassium silicate and sodium/potassium hydroxide, which are known contributors to carbon emissions, hence limiting the advantages of GPC; therefore, reducing the amount of these alkaline activators that contribute to carbon emissions is necessary for developing a more sustainable geopolymer concrete. In this study, the influence of the variation in sodium hydroxide molarities on the performance of fly ash/sugarcane bagasse ash-based-geopolymer concrete was investigated. The different molarities used were 10 M, 12 M, 14 M, and 16 M sodium hydroxide solutions. In addition, the effect of sugarcane bagasse ash content (0%, 5%, 10%, 15%, and 20%) on the fresh and hardened geopolymer concrete properties were examined. The slump test, compression test, split tensile test, and flexure test were conducted on the cast samples. The results of this study showed that raising the concentration of NaOH from 10 M to 16 M while maintaining a sodium silicate to sodium hydroxide ratio of 2.5 resulted in a 3.75–10.2% improvement in compressive strength after 28 days. It is worth noting that, even at a concentration of 10 M, the concrete still achieved high strength.

Red-mud additive geopolymer composites with eco-friendly aggregates

Geopolymers have an increasing importance and a crucial task in engineering, especially structural engineering. Geopolymers are sustainable composites with low carbon emissions rather than cement composites. It leads to be an alternative to cement composites and the structure of geopolymer composites can allow to utilize various industrial and non-industrial wastes and by-products. In this point, there is an unclarity of waste material contributions to the geopolymeric composites and this issue is worth to study and an area of ongoing research. In this paper, it is aimed to produce red mud additive sustainable geopolymer composites with various eco-friendly fillers (brick powder, waste marble powder, glass powder, ceramic powder, and rice husk ash). 28 mixtures were designed, many specimens produced, and tested. In the first step of the experimental stage, the physical, the mechanical and the durability properties were determined and evaluated. At second, the best geopolymer composites were determined with a multi-criteria decision-making method (MCDM). 22 geopolymer parameters were employed in MCDM. As a results, 25% marble dust, 25% brick powder, 75% ceramic powder, 50% rice husk ash and 50% glass powder were the optimum ratios to obtain maximum compressive strength in terms of waste types and the highest compressive strength is obtained for 25% brick powder among the results. The best geopolymer composite was determined as GWGP50 with 50% glass powder + 50% recycled aggregate in a holistic manner with TOPSIS. Results showed that geopolymer GWGP50 had aspects that were open to development.

Sustainable Geopolymer Structural Insulation Panels Obtained with the Addition of Power Plant Ash and Furnace Slag with Potential Uses in the Fabrication of Specialized Structures

The paper describes the process of obtaining geopolymer composites using raw materials from critical waste, i.e., mixed power plant ash and furnace slag powder. Using such geopolymer composites, structural insulation panels were made in the laboratory, which were subjected to tests specific to construction applications. At the same time, some special properties, such as sound insulation and electromagnetic shielding properties for special applications, were tested. The results obtained from the functional tests led to the conclusion that the panels made of geopolymer composites provided both sound and electromagnetic attenuation values clearly superior to those obtained from autoclaved cellular concrete, brick, or concrete structures, which encourages us to suggest such material concepts for complex shielding purposes. The sustainability of the technology for producing such geopolymer composites was fully demonstrated from the economic, environmental, and social perspectives.

Data-driven approach for sustainable geopolymer mortar production with treated sewage sludge

ABSTRACT This paper highlights an innovative approach to address the environmental challenges associated with waste management and construction materials. The study presents a new technique for utilising treated sewage sludge in the production of eco-friendly geopolymer mortar. Sewage sludge is a byproduct generated from wastewater treatment plants that poses significant environmental issues due to its disposal problems. Geopolymer mortar, on the other hand, is a sustainable construction material that can be produced by activating industrial waste materials, such as fly ash, using alkaline activators. By integrating machine learning algorithms and data visualisation techniques, this study optimises the mix parameters of geopolymer mortar while simultaneously reducing the negative impact of sewage sludge disposal. The experimental results show that sewage sludge ash can replace fly ash and fine aggregate in 1:3 geopolymer mortar by up to 30% and 20%, respectively, without any toxic or heavy metal residues. The compressive and flexural strength of the sludge-based mortar were comparable to ordinary geopolymer mortar, while water absorption and drying shrinkage were similar to control specimens. This research offers a unique solution to promote sustainability in waste management and construction industry by utilising waste materials, including fly ash and treated sewage sludge, for geopolymer production.