This study investigates the thermo-mechanical behaviour of alkali-activated concrete (AAC) incorporating a binary binder of fly ash and ground granulated blast-furnace slag under elevated-temperature exposure. The primary objective is to evaluate the influence of sodium hydroxide concentration on mechanical performance, residual strength, and thermal conductivity. Three AAC mixes were prepared with constant sodium silicate content (8

One of the most revolutionary technologies in contemporary building is three-dimensional concrete printing (3DCP), which allows for automated manufacture, minimizes material waste, reduces reliance on labor, and increases construction efficiency. Geopolymer-based binders have garnered a lot of interest among printable cementitious materials due to their significantly reduced carbon footprint, superior durability, chemical resistance, and capacity to use industrial by-products like fly ash, metakaolin, ground granulated blast furnace slag (GGBS), mining waste, and other supplementary cementitious materials. Advances in rheological control, fiber reinforcement, nanomaterial inclusion, extrusion-based and powder-based additive manufacturing techniques, the use of industrial waste, and the improvement of printable geopolymer composites' mechanical performance have all been documented in numerous studies. The literature that is currently available, however, is still very dispersed; instead of establishing integrated relationships among material composition, rheological evolution, printing parameters, interlayer bonding, durability, and structural performance, the majority of studies concentrate on isolated aspects like printability, rheology, strength development, or sustainability. Additionally, the widespread use of 3D printed geopolymer concrete is limited by the lack of defined mix design techniques, widely recognized printability indices, rheological characterization procedures, and long-term durability evaluation. By combining research on material design, rheological behavior, fresh-state performance, mechanical properties, fiber and nanomaterial modification, industrial waste valorization, sustainability evaluation, and structural applications, this review critically synthesizes recent advances in geopolymer-based additive manufacturing. Predictive mix-design frameworks, coupled rheology–printing models, standardized testing procedures, multi-scale durability evaluation, machine learning-assisted optimization, life-cycle assessment integrated with structural performance, and field-scale validation are among the significant research gaps identified by the critical analysis. Lastly, new research avenues are suggested to help develop geopolymer-based additive manufacturing systems for next-generation smart infrastructure that are dependable, sustainable, and economically feasible.

Urban Air Mobility, or UAM, is no longer a futuristic concept confined to science fiction. With several eVTOL aircraft nearing certification in the United States and Europe, the question for countries like India is not whether this technology will arrive, but whether we are ready for it. This paper proposes a practical assessment tool-the UAM Ecosystem Readiness Index (UAM-ERI)-designed specifically for the messy, complex realities of emerging economies. Unlike existing frameworks that assume a certain baseline of regulatory sophistication and infrastructure maturity, the UAM-ERI accounts for the institutional fragmentation, income disparities, and infrastructure gaps that characterize markets like India. The framework evaluates six interconnected dimensions: Regulatory Maturity, Infrastructure Preparedness, Technological Capability, Economic Viability, Social Acceptance, and Environmental Sustainability. Each dimension is weighted through an Analytical Hierarchy Process involving 18 domain experts. Applying this framework across five Indian metros-Delhi-NCR, Mumbai, Bengaluru, Hyderabad, and Chennai-the study finds that India's technology talent and market size represent genuine strengths, but regulatory clarity and physical infrastructure lag far behind. Bengaluru scores highest overall (0.548), yet even this puts it squarely in the "developing readiness" band. The paper closes with a phased 2026-2035 implementation roadmap grounded in these findings.

This study aims to explore how leaching impacts the microstructure of a selected fly ash-derived geopolymer and evaluate its potential for near-surface disposal of radioactive waste. The uniqueness of this geopolymer formulation is its ability to form an aluminosilicate network that remains resistant to structural changes upon contact with water. The leach index of base elements such as Ca, Al, Na and Si was between 11 and 13, suggesting that the formulation is superior to Portland cement or conventional hydraulic cement. Solid-state NMR reveals that the water-interacted specimen has no contamination of the zeolite phase and all the Na is incorporated into the aluminosilicate geopolymer gel network, which also confirms that the glassy network of the geopolymer is responsible for imparting low leachability of base elements from its structure, and there is no labile sodium available for exchange as in zeolites.

Porous materials are being studied for applications in the construction sector. Although porous concrete is currently produced using autoclave processing, the latter drastically reduces the chance of material sustainability due to energy consumption. Thus, research focusing on low-cost raw materials and efficient energy in making porous geopolymer is vital for porous geopolymer industrial implementation. The present study focuses on producing porous geopolymer from industrial wastes such as fly ash and calcium-containing slag at room temperature. The authors assessed the effects of incorporating granulated blast furnace slag, Linz Donawitz slag, and argon oxygen decarburization slag with fly ash on geopolymer properties. The developed geopolymer exhibited a bulk density range of 0.7-1.12 g/cm(3), compressive strength of 4-11 MPa, pore volume of approximately 30-75%, thermal conductivity of 0.1-0.4 W/mK, and pore size between 1 nm-1 mm. The mechanical strength of porous geopolymers is influenced by factors such as raw materials, pore size distribution, and porosity. Comparison with commercial products revealed favorable mechanical properties. The GBFS's glass content and reactivity are higher than AOD and LD slag. Pore size distribution suggests macropores size and isolated pores within geopolymer. A mathematical model is devised to calculate compressive strength, density, and average porosity. Using GaBi software (version 8.5.0.79) with an Indian extension database, the environmental benefits of porous and normal-weight building materials during transportation are evaluated. Additionally, the porous geopolymer's comprehensive cost is Indian Rupee9400/m(3).

In an attempt to develop glass ceramics during the direct cooling of molten blast furnace slag, its solidification and crystallization behavior are studied using the JMAK model and experimental techniques. The maximum rate of crystallization occurs at a higher heating rate (20 ℃/min). Mold materials (copper, iron, graphite, and sand) with different thermal conductivities are used to control the cooling rate of molten slag. XRD analysis shows that, in the slowest cooled sample, gehlenite, akermanite, and calcium aluminum magnesium silicate are formed as a crystalline phase (80

Ironmaking- steelmaking is a material and energy intensive process with a resource efficiency of only - 33 %. Resource efficiency enhancement requires recovering the wasted/unutilized material by-products and the energy associated with them in various forms. This review attempts to identify the material leakages and energy losses at each step of steelmaking (from iron ore mining) and explores approaches to plug the energy and material leakage; material efficiency brings in energy savings indirectly. Besides the material loss, accumulation of the byproducts (slime/tailings, steel slag, etc.), carbon emission, etc., cause environmental and ecological damage. The review discusses the prospects of slimes/tailings beneficiation through physical and physicochemical methods (often after some pretreatments). The manuscript also discusses the need to recover heat from molten slags (BF slag and BOF slag) to reduce the energy intensity. Further, it discusses the endeavors to overcome the latent hydraulic activity of granulated BF slag and ways to enhance the acceptability of BOF slag in different applications. A brief sum-up of global efforts towards net zero emission (in line with the Paris Declaration) through carbon recycling, low emission intensity processes, alternate fuels, etc., is included. Lastly, the authors list the challenges of the Indian iron & steel industry and the efforts from the government and steel industries towards achieving the projected crude steel production (300 million tons) without crossing the emission intensity thresholds (Paris Declaration). The endeavors strengthen the sustainability of the steel industry.

This paper investigates the behavior of feldspar-based geopolymer mortars under nitric acid, sulfuric acid attack and seawater attacks and provides an understanding of their degradation mechanisms. Geopolymer mortars were cast using feldspar quarry waste (pegmatite) altered with 20–30 wt

In order to overcome the brittle behavior of conventional geopolymers, of late, a paradigm shift towards development of hybrid geopolymers has commenced. This study describes hybrids synthesized by co-milling metakaolin and solid organics (epoxy resin: diglycidyl ether of bisphenol A and hardener: dicyandiamide) followed by alkali activation. The developed hybrid geopolymers exhibit enhanced mechanical and physical properties. Physical and mechanical properties of such hybrids depend on the extent of molecular-level interactions and microstructural evolution during geopolymerisation. Evolution of molecular structure from precursor stage (co-milled samples) to hybrid geopolymers is studied using transmission electron microscopy (TEM) and 27Al, 13C, 29Si solid-state nuclear magnetic resonance (NMR) spectroscopy. NMR and TEM analyses of the hybrid geopolymers illustrate the formation of Si–O–C bonds and uniform C distribution (with no phase separation); this confirms inorganic–organic chemical interactions during geopolymerisation. Detailed assessment of pore characteristics using TEM, mercury intrusion porosimeter, and Brunauer–Emmett–Teller reveal formation of a dense gel (with reduced pore size and pore volume) in hybrid geopolymer vis-à-vis MK-based inorganic geopolymer. The implication of such microstructural features on mechanical and physical properties is discussed. Lastly, the suitability of developed hybrids as fire-retardant materials used in mass transit applications is highlighted.

New challenges are arising everyday due to the waste management problems. Construction is one of the most important activities and it is seen as a real threat to sustainable development considering permanent use of limited natural resources and the disposal of huge amount of debris. Construction and demolition wastes contain aluminosilicates as major constituents. In this study an attempt has been made to investigate the mechanical effect of the addition of metakaolin and lime to synthesize geopolymer using construction waste. The compressive strengths of the geopolymer products developed at 28 days from brick dust, metakaolin and lime with activator solution were found 8.35, 21.30 and 25.0 MPa, respectively. Addition of metakaolin and lime had increased the compressive strength by more than 2.5 and 3.0 folds respectively in comparison to the product obtained from brick dust only. The FTIR spectra and SEM-EDX micrographs of the reaction had shown structural changes and formation of aluminosilicate hydrate and calcium silicate hydrate gel. Geopolymer synthesized from brick dust was found very hard ceramic like product with potential applications such as pavement blocks, tiles, retaining walls etc.

In this investigation, mechanical activation (MA) of pegmatite quarry wastes was perform via an eccentric vibratory mill to improve the geopolymeric reactivity. The MA at miscellaneous times (0 to 90 min) resulted in different activation degrees of samples with improved the fineness of particle size and specific surface area from 2.974 to 5.311 m2.g−1. Geopolymer binders were synthesized by partly replacing the pegmatite quarry waste with 12.5 wt% of metakaolin. The activating solution used was a mixture of 10 M NaOH and Na2SiO3 solution with a volume ratio of 1:1. Reaction kinetics, compressive strength, water absorption, chemical (FT-IR, XRD, 27Al and 29Si MAS NMR), and microstructural (SEM/EDS and TEM) analyses were done to characterize the obtained geopolymer binders. The microstructural characterization reveals that undissolved/unreacted particles decreased while the non-bridge particles increased with pegmatite milled. Under SEM/EDS and TEM, fineness of pegmatite particles is highlighted by the formation of more reaction product. As a result, the compressive strength of geopolymer binders improved from 22.3 to 51.6 MPa for 0 to 60 min of milling. From these results, there is feasibility of valorising feldspathic (pegmatite) quarry wastes as alternative aluminosilicate precursors to develop environmentally-friendly geopolymer binders. The resulting binders with high-strength and low water absorption (≤ 8.6%) associated to minimization of CO2-emissions can be used as potential candidate in structural applications.

In this comprehensive study, we explore the multifaceted world of green sustainable construction, highlighting innovative techniques and materials. This article presents an insightful exploration of green sustainable construction, focusing on the crucial aspects of architectural design, judicious material selection, and the adoption of optimal structural designs. Through comprehensive literature research supplemented by practical examples, it highlights several innovative construction methodologies that are at the forefront of green sustainable development. These include the use of lightweight framing, cladding systems, autoclaved aerated concrete (AAC), rammed earth, and straw bale construction, each contributing uniquely to environmental sustainability. The study brings to light the looming issue of raw material scarcity due to excessive exploitation, urging for sustainable material management in construction. It stresses the urgency of implementing effective pollution control measures within the construction sector, asserting that such practices are not just beneficial but essential for environmental conservation and sustainable development. This research contributes significantly to the field by providing a foundation for future exploration and advancements in sustainable construction practices.

Fly ash is a light byproduct produced when pulverized coal is burnt in suspension-fueled furnaces in power plants. Separating the recovered fly ash from the exhaust gases. Due to its distinct physical and chemical properties, it is utilized in a wide variety of industrial and building applications. These applications include the production of cement and concrete, the stabilization of liquid waste, and hydraulic mining backfill. Fly ash has the potential to enhance the physical and mechanical properties of aluminum castings, as well as reduce their costs and increase their densities, all while lowering their prices. This research investigated the effect of fly ash incorporation on the mechanical properties of the aluminum casting alloy ZA8. Investigated were the cast and heat-treated varieties of unreinforced ZA8 and its metal matrix composite of 15% ferrous, 20% nickel, 10% fly ash, and 10% magnesium carbide. According to the results, the quantity of fly ash in the melt affected the tensile and impact properties of the metal matrix composite. The loss of magnesium atoms in the matrix, which contributes to the strength of solid solutions, and porosity both contribute to the lower mechanical properties and impact resistance of the metal matrix composite.

This study’s main objective was to assess a newly built magnetorheological hammer for use in core and ultrasonic probe velocimetry (UPV) testing to determine the compressive strength of RC. By reusing or recycling existing materials, reinforced concrete has been found to reduce building costs and have a smaller negative impact on the environment. On the other hand, well-established techniques for determining material strength without breaking it include magnetorheological hammer and core testing. This study set out to determine the compressive strength of RC using the suggested methodology and compare the results to those attained using 150 mm core specimens. To do this, three different types of concrete were created. The OPC, river sand, and natural aggregate (crushed granite) were used to make concrete. These concrete mixtures, which contained aggregates no larger than 20 mm, were poured in order to evaluate a newly designed magnetorheological design using UPV, core, and hammer methods. Using this multi-faceted strategy, correlations between UPV, core testing, and magnetorheological (MR) hammer were also obtained. These results are more encouraging than those from the rebound hammer test, which showed that it was impossible to anticipate with any degree of accuracy the compressive strength of the RC.

Geopolymers in radioactive waste management have in recent times gained dominance in disposal module acceptance. Here is a comparative study on formulations prepared from industrial wastes to be utilized as radionuclide disposal barriers in near surface disposal facilities (NSDFs). Different tools such as isocalorimetry, compressive strength, chemical durability were utilized for screening the formulations. Water leaching of the samples shows that the release of the ions to the leachant is minimal. Durability studies in acids (H2SO4, HCl and HNO3) show that the samples are mostly acid resistant. X-ray tomography suggests low pore volume change over a period of 2 years. The study concludes that the NSDF requirement of low permeability of water and better chemical durability criterion is met by the optimized geopolymerization formulation.

Currently, the building industry is focusing on the requirement for high energy utilization. It is critical to optimize energy use by utilizing renewable resources. The use of phase-change materials in thermal energy storage systems is gaining popularity in passive applications for green buildings due to their innovative approach. The proposed work focuses on the incorporation of MWCNT additive sodium poly acrylate as PCM materials into the walls, panels, and roofs of passive structures, as well as the assessment of optimal energy consumption in green buildings via indoor environmental quality (IEQ). A novel framework was developed using the response surface method and the hill climbing technique to identify the most efficient use of energy output, charging time, and heat transfer rate based on the input phase such as input air condition temperature (25–28 °C), air conditioner flow rate (100–600 cfm) and relative humidity (35–55