Search Results (1,054)

The development of carbon-neutral construction materials has stimulated interest in alkali-activated systems for the valorization of industrial non-hazardous waste. This study proposes an original comparative approach to assess the cementing reactivity of several wastes, including black and white fly ash, bottom ash, fine glass dust, and float-glass polishing sludge, through their use as partial replacements for metakaolin (MK). Formulations containing 5–50 wt% of fine waste powders (<45 μm) were prepared and mechanically compared with a reference MK-based geopolymer. Formulations containing waste additions to the reference geopolymeric paste were also evaluated to investigate their role as aggregates/fillers. Mechanical testing identified float-glass polishing sludge as the most reactive precursor, achieving a compressive strength of 25 MPa at 10 w% addition, compared with 16 MPa for the reference material. Bottom ash and black and white fly ash reached approximately 19–21 MPa at 5–10% replacement or addition. Conversely, bottom ash at substitution levels above 5% reduced mechanical performance owing to its high crystallinity and unfavorable Si/Al molar ratio. Microstructural characterization by XRD, FT-IR, density measurements, and SEM was correlated with the observed cementing activity. These results provide a basis for performance-based design criteria aimed at the sustainable valorization of locally available industrial by-products in alkali-activated materials. Full article

Offshore buried-hill reservoirs are potential targets for integrated CO₂-enhanced oil recovery and geological storage. However, the early-stage response of clay-rich granitic gneiss under reservoir conditions remains poorly constrained. We conducted 7-day static experiments with an illite-rich mineral powder assemblage at 125 °C and 35 or 50 MPa using synthetic formation water. Complementary granitic gneiss discs were reacted at 50 MPa for surface observations. The powders were characterized by XRD, FTIR, and XPS and the discs by SEM–EDS. XRD indicated lower relative abundances of illite after reaction and more pronounced changes in several carbonate and clay phases at 50 MPa. FTIR showed the attenuation of structural O–H, carbonate, and aluminosilicate-related bands, while XPS indicated surface elemental redistribution. SEM–EDS revealed mineral-selective surface alteration and localized particle accumulation. Quartz appeared less reactive than clay minerals and calcite over the experimental duration. The particles may include redeposited fines or secondary products, but their phase identity remains unresolved. Together, the observations characterize early-stage mineralogical and surface responses relevant to evaluating CO₂–rock interactions in clay-rich buried-hill reservoirs. Their consequences for injectivity and long-term storage require direct petrophysical and geomechanical evaluation. Full article

Bottom slag (BS), a coal combustion by-product, is an underutilized aluminosilicate resource with potential for alkali activation. In this study, the physicochemical characteristics of BS, including its chemical composition, mineralogy, morphology, and activity index, were systematically evaluated, and ground BS was blended with ground granulated blast-furnace slag (GGBFS) to prepare alkali-activated binders. The effects of BS content on mechanical properties, reaction products, and microstructural evolution were investigated using compressive strength tests and multi-scale characterization techniques. The results showed that BS contains abundant amorphous aluminosilicate phases with low residual carbon and exhibits considerable latent cementitious activity despite its relatively low intrinsic reactivity. The mechanical performance of the binders was strongly governed by precursor composition. Incorporating 20–40 wt.% BS achieved the optimum balance between precursor reactivity and strength development, whereas higher BS contents significantly inhibited alkali activation reaction because of the dilution of reactive glassy phases. Strength development was closely associated with the formation of C-(A)-S-H and N-A-S-H gels and the development of a dense microstructure. These results demonstrate that the synergistic activation of BS and GGBFS provides an effective route for producing low-carbon alkali-activated binders while enabling the high-value utilization of coal-fired BS. Full article

This paper investigates the possibility of pressure-assisted thermomechanical consolidation and thermal treatment without applied pressure during the low-temperature consolidation of oil-saturated aluminosilicate sorbents for their subsequent application in the conditioning of liquid oil-containing radioactive waste (RAW). The Premium and Absorbent sorbents saturated with transformer oil not containing radionuclides were used as model RAW systems. It was established that pressure-assisted thermomechanical consolidation leads to the formation of a denser structure and a reduction in hydrocarbon-phase losses compared with thermal treatment without applied pressure. For Premium, mass losses decreased from 0.74 to 0.35 g (by 53%), and for Absorbent, from 0.75 to 0.47 g (by 37%), and the consolidated samples were characterized by a more homogeneous microstructure and increased resistance to exudation. It was established that the efficiency of hydrocarbon-phase retention is determined by both the treatment conditions and the mineral composition of the sorbent. The obtained results indicate the prospects of low-temperature pressure-assisted thermomechanical consolidation at a temperature of 150 °C, a pressure of 1.5 MPa, and a holding time of 20 s for the conditioning of oil-containing RAW without the use of additional binding components. Full article

The cement industry is a major source of global CO₂ emissions, driving the development of low-carbon alternatives such as geopolymers. This study examines geopolymer binders produced from ceramic brick waste (CBW) and metakaolin waste (MKW), evaluating their fresh and hardened properties as well as their performance under elevated temperatures. Five binder compositions were formulated by progressively replacing CBW with MKW (25–100 wt.%). The alkaline activator ratio (Na₂SiO₃/NaOH = 1.5) and NaOH molality (8 M) were kept constant. Fresh-state behavior was evaluated using Suttard viscometry and Vicat testing, while hardened-state performance was assessed through compressive and flexural strength, softening coefficient, and drying shrinkage. Thermal resistance was examined at 200, 400, 600, and 800 °C, supported by XRD, FT IR, and SEM analyses. The present study investigates how waste-derived aluminosilicate precursors with differing crystallinity and reactivity affect geopolymerization mechanisms and high-temperature phase evolution. MKW-rich binders were found to form highly reactive amorphous gels, resulting in superior early mechanical strength, whereas CBW-rich binders retained thermally stable crystalline phases that enhanced resistance to structural degradation at elevated temperatures. The MKW-rich formulation (F5) demonstrated the highest ambient mechanical performance, reaching 82.8 MPa after curing at 200 °C, due to intensified secondary geopolymerization. In contrast, the CBW-only binder (F1) exhibited superior thermal stability, maintaining a compressive strength of 46.4 MPa even after exposure to 800 °C. These findings establish a clear structure–property relationship between precursor mineralogy, gel chemistry, and high-temperature performance, offering valuable insights for the tailored design of waste-derived geopolymers with optimized thermal and mechanical properties. Full article

Lithium aluminosilicate (LAS) ultra-low-expansion glass ceramics are core materials for precision optical systems, whose quality and dimensional stability are critically constrained by the uniformity of the coefficient of thermal expansion (CTE). This work proposes a nondestructive ultrasonic immersion pulse reflection (UIPR) method for rapid and low-cost characterization of the CTE in LAS glass ceramics. Key parameters of the ultrasonic measurement system are optimized via finite element method (FEM) simulations and experimental validation. Employing the correlation method, the ultrasonic longitudinal wave velocity is measured in LAS glass ceramic samples with distinctly different CTE values. The proposed method achieves an ultrasonic longitudinal wave velocity measurement uncertainty of 0.49 m/s, contributing 4.78 ppb/°C to the overall uncertainty of ultrasonic CTE determination. Within the investigated sample set, a negative relationship is observed between ultrasonic longitudinal wave velocity and the mean CTE (0–50 °C). The linear fit yields a slope of −9.75736 (ppb/°C)/(m/s), with a Pearson correlation coefficient of −0.84303. Featuring noncontact and nondestructive capabilities, this method lays a solid methodological foundation for CTE evaluation and efficient iterative optimization of material fabrication processes. Meanwhile, it shows great potential for rapid full-aperture characterization of CTE uniformity in large-size LAS glass ceramics. Full article

This review critically evaluates glass-ceramics derived from aluminosilicate solid wastes through the linked framework of raw-material chemistry, the processing route, microstructure, thermal performance, and environmental safety. Waste-derived CaO–Al₂O₃–SiO₂ (CAS) and CaO–MgO–Al₂O₃–SiO₂ (CMAS) systems currently provide the most developed basis for dense and porous building products, whereas evidence for other compositional systems remains less mature. Across these materials, phase assemblage, residual-glass connectivity, crystallized pore-wall integrity, and pore structure jointly govern thermal stability, heat transfer, dimensional stability, cracking behavior, and mechanical-property retention after high-temperature treatment. Bulk crystallization and powder sintering are the principal demonstrated preparation routes, although their applicability depends strongly on waste composition, glass-forming ability, and processing windows. Future studies should integrate multi-source waste design, low-energy processing, standardized thermal and mechanical characterization, long-term leaching assessment, and life-cycle analysis to establish reliable performance and environmental boundaries for practical applications. Full article

Zeolites are crystalline microporous aluminosilicates whose tunable porosity, ion-exchange capacity, surface charge, and chemical robustness make them versatile materials at the biointerface. This review surveys three converging domains of zeolite biomedicine. First, haemostasis and wound healing, where water adsorption and Ca²⁺ release drive procoagulant activity, from the QuikClot generation to strategies that mitigate the exothermic response and to flexible zeolite–textile dressings. Second, the separation, immobilization, and sensing of biomolecules, where external surface area, hierarchical porosity, and surface chemistry—rather than intracrystalline sieving alone—govern the interaction with proteins and nucleic acids in complex matrices. Third, the emerging design of zeolite-based theranostic platforms integrating drug delivery, imaging, and stimuli-responsive therapy, enabled by the transition from bulk crystals to surface-engineered nanozeolites. Across all three domains, a single lesson recurs: the biological behaviour of zeolites is governed by the external surface rather than by molecular sieving, and the chemical integrity of the framework under working conditions is a design parameter that is reported only sporadically. We further show that the theranostic literature reaching in vivo validation is dominated by zeolite-like imidazolate frameworks, whereas the evidence for aluminosilicate zeolites remains largely in vitro—the gap that most urgently needs closing. The successes of ZIFs should therefore be read as structural inspiration for zeolite design rather than as direct evidence for aluminosilicate clinical translation. Full article

The mounting requirement for sustainable construction materials has augmented the development of geopolymer binders incorporating agricultural wastes. Unlike the previous studies on individual agricultural ashes, this study investigates the viability of combined use of sugarcane bagasse ash (SCBA) and jackfruit leaf ash (JLA) in fly ash-ground granulated blast furnace slag (GGBFS)-based geopolymer binders under ambient curing conditions. Five mixtures with varying proportions of SCBA and JLA were evaluated for their fresh (flow, setting time, fresh density and rise in temperature), hardened (compressive strength and flexural strength) and microstructural characteristics (FESEM-EDS, XRD, FTIR and TG/DTG analyses). The incorporation of 10% SCBA and 10% JLA of the total binder (M3 mixture) was found to produce best performing performance, resulting in a maximum 28-day compressive strength of 64.83 MPa and flexural strength of 7.25 MPa, corresponding to increments of 36.5% and 73.0%, respectively, over the control mix. The formation of a dense reaction matrix along with enhanced geopolymerization and thermal characteristics were also observed for the best performing mixture through microstructural studies. The outcome of this investigation reveals that the utilization of agricultural ashes (SCBA and JLA) can be an efficient supplementary aluminosilicate precursor to develop high-performance geopolymer binders. Full article

Cement production is associated with substantial carbon dioxide (CO₂) emissions due to the high material and energy intensity of Portland clinker manufacture. Partial clinker replacement with supplementary cementitious materials is one of the most promising strategies for reducing the carbon footprint of cement; however, the thermal activation of aluminosilicate raw materials does not always yield highly reactive products. In this study, a pillaring approach is proposed as a controlled method for modifying the structure of clays and unlocking their latent reactivity. Different clay types—namely, kaolinitic, montmorillonitic, and illite–chlorite clays—were sequentially treated with an aluminum sulfate solution and calcined at 650 °C. Their phase composition and microstructure were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM), while specific surface area was determined by BET analysis and pozzolanic activity. The results showed that pillaring doubled the specific surface area of montmorillonitic (2:1) and illite–chlorite (2:1:1) clays. Replacing 30% of clinker with pillared clays and limestone increased the compressive strength to 86.5 MPa and the flexural strength to 34.6 MPa. The developed low-carbon composite cements also exhibited high durability: the density of the hardened cement mortar increased to 2.410 g/cm³, the strength loss after 200 freeze–thaw cycles decreased to ≤5.5%, and the sulfate resistance coefficient (Ks) increased to 0.98 (with minimal expansion of the samples <0.02%). The proposed approach makes it possible to reduce the carbon footprint of cement by 25–30% while enabling the use of locally available raw materials for the production of competitive low-carbon green cements. Reported reductions of this order are broadly consistent with the known effect of lowering clinker content through supplementary cementitious materials in blended cement systems. Full article

The production of carbonaceous materials from agro-food byproducts, i.e., olive stone and molasses alone or in combination with aluminosilicate minerals, i.e., zeolite, was investigated. Two different dyes, i.e., methylene blue (MB) and C-phycocyanin (C-PhC) contained in Spirulina extract, were used for the examination of the adsorptive properties of the materials. The combination of the Brunauer–Emmett–Teller surface area, X-ray diffraction, and X-ray photoelectron spectroscopy provides a comprehensive profile of composite sorbents. Several key factors, including initial dye concentration, pH, contact time, temperature, and sorbent, were investigated. All the produced adsorbents have shown a highly disordered carbon structure with specific surface areas between 16 and 1211 m²/g. The elemental composition analysis revealed the presence of C-C, C-H, C-O, C=O, O-C=O, and (CO₃)²⁻ bonds during high-resolution C1s and O1s deconvolution and detected the elements Al, Si, Na, Ca, K, Na, and S, confirming the aluminosilicate framework of the zeolitic structure of the materials. The examined conditions showed the best MB and C-PhC adsorption results at pH 8, temperatures of 50 °C and 40 °C, respectively, an initial concentration of 0.5 mg/L for MB and 32 mg/L for Spirulina extract (SE), and a sorbent dosage of 2.0 g/L C/MB or SE solution. The adsorbents produced were applied to the removal of C-PhC from industrial waste. To conclude, this research underscores the viability and high efficiency of repurposing agricultural waste into carbonaceous composite sorbents to eliminate dyes from wastewater. Full article

One-part geopolymer has emerged as a promising alternative to ordinary Portland cement. In this study, the effect of CaO dosage on the compressive strength of one-part geopolymers was systematically investigated, and its underlying modification mechanism was revealed via multi-scale characterizations including XRD, FTIR, TG, NMR and nitrogen adsorption–desorption. The results show that the compressive strength of the samples at all curing ages exhibits a trend of sharp initial decrease, followed by a slight rebound, and then a secondary decline with the increase in CaO dosage. All CaO-containing specimens exhibit significantly lower strengths than the CaO-free reference. Specifically, the reference sample achieves the highest 28-day compressive strength of 56.6 MPa. The strength of the sample at each curing age drops to the minimum at 5% CaO dosage, with a 28-day strength of only 17.9 MPa. Partial strength recovery of the sample is achieved at 7.5% CaO dosage. The strength deterioration is mainly attributed to the rapid hydration of CaO, which consumes free water and reactive silicon and hinders the generation of N-A-S-H gel rather than directly disrupting the aluminosilicate network. Meanwhile, the hydration products are continuously carbonated to form calcium carbonate, and the carbonation-induced volume expansion at excessive dosage may induce microcracks in the matrix that impair the structural integrity. Only at a moderate dosage of 7.5% CaO can a slight strength rebound be realized through the possible formation of C-S-H-type phases and the pore-filling effect. This study provides a theoretical basis for the material design and performance regulation of one-part geopolymers. Full article

To enhance the application value of sand washing residue mud (SWRM) and mitigate its adverse environmental impacts, this study focuses on the resource utilization of SWRM. The research employed a combined mechanical–thermal activation method to enhance the activity of SWRM and utilized the mixed optimal design module to design and optimize the mixing ratio of SWRM-based LC3 cement. The results showed that within a ball-milling time range of 3–9 min, as the ball-milling time increased, the specific surface area increased, the median particle size D₅₀ decreased, and the particle size was mainly concentrated within the range of 0.1–30 μm; the specific surface area of the washed sand residue after 3 min of grinding reached 1080 m²/kg, with D₅₀ being 3.50 μm, which met the requirements for making cementitious materials. After thermal activation at temperatures ranging from 450 °C to 950 °C for the 3 min ground SWRM, the 28 d activity index showed a trend of increasing first and then decreasing with the increase in calcination temperature, and the 28 d activity index reached the maximum of 79.3% at a calcination temperature of 650 °C. The optimal mixing ratio of the AC70 group’s SWRM-based LC3 cement obtained through the mixing design was: cement clinker 66.5%, desulfurized gypsum 3.5%, activated SWRM 15%, and limestone powder (LP) 15%. The 28 d compressive strength of the AC70 group’s SWRM-based LC3 cement was 34.1 MPa, with initial setting and final setting times of 170 min and 240 min respectively, and the volume stability was qualified. The microscopic test results indicated that under the synergistic effect of alkali and salt, the silicate and aluminosilicate tetrahedral structures in the active sand-washed mud (ASWRM) decomposed, forming a C-(A)-S-H network structure, which was the main source of strength for the SWRM-based LC3 cement in the later stage. The ecological benefit calculation and analysis showed that compared with ordinary Portland cement of the same grade, the AC70 group’s SWRM-based LC3 cement had a 27.6% reduction in implicit energy consumption, a 44.1% reduction in carbon emissions, and a 25% reduction in cost. This study provides an innovative approach for the high value-added resource utilization of SWRM. Full article

Problematic fine-grained soils exhibit low strength and inadequate durability, highlighting the need for sustainable stabilization using eco-friendly binders. This study examined the strength development and durability of a natural CH soil (NSs) stabilized with fly ash (FA) based geopolymer exposed to sulfate attack and freeze–thaw (F–T) cycles. The effects of FA content (0–40%) and NaOH molarity (0–10 M) on unconfined compressive strength (UCS) were evaluated after 1, 7, 28 and 56 days of curing. Durability was assessed separately under accelerated laboratory conditions after 1, 3, 5, 7 and 11 F–T cycles and 7, 28 and 56 days of sulfate exposure. In non-activated specimens, FA contents of up to 30% enhanced the UCS primarily through the microfiller effect and possible time-dependent pozzolanic reactions. Alkali activation promoted the development of a compact binding matrix through the dissolution and polycondensation of aluminosilicate precursors, with the microstructural and chemical observations being consistent with the possible formation of C-(A)-S-H and/or N-A-S-H-type reaction products. F30M8 exhibited the highest strength, reaching a 56-day UCS of 1488.58 kPa compared with 282.46 kPa for untreated NSs. F30M8 retained approximately 94% of its UCS after 11 F–T cycles and 92% after 56 days of sulfate exposure. XRD, FTIR, and SEM-EDX analyses provided evidence of aluminosilicate restructuring and the development of a dense microstructure under alkaline activation. This refined matrix may have contributed to limiting sulfate- and ice-crystal-induced deterioration, thereby helping to preserve the structural integrity of the FA-based geopolymer-stabilized NS specimens, whereas untreated and non-activated FA-stabilized specimens disintegrated under sulfate exposure. These findings indicate that FA-based geopolymer stabilization has considerable potential for natural CH soil under the laboratory exposure conditions investigated in this study. Full article

This study developed alkali-activated binders based on biomass power plant ash (BPPA) and ground granulated blast furnace slag (GGBFS) for potential application in coal-mine goaf backfilling. Five precursor proportions, ranging from 100% BPPA to 100% GGBFS, were investigated to clarify the influence of precursor composition on fresh properties, mechanical performance, reaction-product evolution and microstructural development. Increasing the GGBFS content reduced slump and shortened both initial and final setting times, indicating accelerated precursor dissolution and early structural build-up. Compressive strength increased nonlinearly with GGBFS incorporation. Multiscale characterization consistently demonstrated that GGBFS promoted the transformation of the initially quartz-rich and weakly reactive BPPA system into a calcium-rich aluminosilicate binding matrix. This transformation was accompanied by changes in the Si-O-T bonding environment, increased formation of hydrated reaction products and progressive filling and bridging of the spaces between residual precursor particles. Consequently, the hardened matrix evolved from a porous particle-supported structure containing isolated reaction regions into a compact gel-supported network that contributed to more effective stress transfer within hardened matrix. Among the investigated mixtures, the formulation containing 25% BPPA and 75% GGBFS exhibited a favorable combination of BPPA utilization, processability, and mechanical performance, indicating its potential for further evaluation in coal-mine goaf backfilling applications. Full article