Search Results (3,561)

Glazes primarily utilize raw minerals like kaolinite. However, considering sustainable development, employing industrial solid waste offers greener design solutions and high economic efficiency. This study employs multiple analytical methods, including XRF, XRD, and SEM, to investigate the feasibility of replacing traditional glaze materials entirely with solid waste. It elucidates the mechanisms underlying changes in texture and color resulting from alterations in microstructure and chemical composition. Research on five different ratios of ceramic glaze composed of fly ash, blast furnace slag, silica fume, coal gangue, and desulfurization gypsum reveals that the implementation of solid waste-based glazes is feasible. The glazes formed a SiO₂–Al₂O₃–CaO system surface, all exhibiting anorthite and diopside as the primary crystalline forms. The results are as follows: 1. The content of Ca and Mg depends on the overall proportion of elements, with a Ca threshold of approximately 28%. Below this threshold, characteristics such as surface roughness and porosity are observed. Above this threshold, as seen in G3 and G4, crystal distribution becomes more dense. 2. Si is the key factor controlling crystal variation. Sample G5 exhibits good crystal continuity. Visually, its color appears distinctly deep red. 3. Samples G1 and G2 both contain approximately 4.8 wt% Fe₂O₃, but G2 exhibits more crystalline precipitation. Visually, G2 appears more reddish-yellow than G1. Higher crystallinity yields superior coloration. Full article

A low-titanium-slag-based multi-solid-waste cementitious system was developed for cemented paste backfill. The cementitious binder was prepared from low-titanium slag (LTS), steel slag (SS), municipal solid waste incineration (MSWI) fly ash, and flue gas desulfurization gypsum (FGDG), while lead–zinc tailings were used as the aggregate for backfill materials preparation. The activation of low-titanium slag, proportion optimization, and strength development mechanisms were systematically investigated. Mechanical grinding effectively activated low-titanium slag, and its activity index reached 108% after 90 min of grinding at 28 d. Steel slag alone could not fully activate low-titanium slag in the ternary system, whereas the incorporation of MSWI fly ash significantly enhanced the synergistic activation effect. The quaternary system with 40% MSWI fly ash replacement showed higher cumulative heat release and better later-age strength. The optimum backfill proportion was a solid mass concentration of 81% with a binder-to-tailings ratio of 1:4, yielding a 28 d compressive strength of 11.07 MPa with satisfactory flowability and setting behavior. Microstructural results indicated that the continuous formation of ettringite and gel phases promoted pore refinement and matrix densification. Moreover, the leaching concentrations of Pb, Zn, Cr, and soluble Cl were all below the relevant groundwater quality limits. These results demonstrate a feasible route for the high-value co-utilization of low-titanium slag and MSWI fly ash in cemented backfill materials. Full article

This paper presents the numerical modeling and experimental testing of steel-reinforced columns composed of three types of concrete: reinforced cement concrete (RCC), geopolymer concrete (GPC), and geopolymer concrete incorporating quarry rock dust (GPCD). GPC columns were produced using fly ash (FA) and furnace slag (SG) in equal proportions (50% each), with the addition of 0.75% steel fibers by volume. In GPCD columns, 20% of SG was replaced with quarry rock dust (QRD). A total of twenty columns (200 mm × 200 mm × 1000 mm), designed for a compressive strength of 40 MPa (fc’), were tested under static loading. The experimental data were validated using finite element (FE) modeling in ABAQUS, where the Concrete Damaged Plasticity (CDP) model was adopted to describe concrete behavior. Calibration of the FE model for the control specimen was carried out by adjusting viscosity parameters, dilation angles, shape factors, plastic potential eccentricity, stress ratios, and mesh sizes. The calibrated control model was then employed for comparative analysis and validation against experimental results. For concentrically loaded columns, the predicted axial load and axial and lateral deflection responses closely matched the experimental observations. However, for eccentrically loaded columns, the FE model over-predicted the load-carrying capacity as well as axial and lateral deflections. The experimental findings indicate that both GPC and GPCD columns exhibited lower load-carrying capacities compared to RCC columns; however, the inclusion of steel fibers enhanced their performance. Overall, the proposed FE model demonstrated a good agreement with experimental observations, providing a reliable framework for predicting the structural behavior of geopolymer-based columns. Full article

The growing demand for sustainable construction has highlighted the need to effectively utilize solid waste materials in concrete production, yet achieving satisfactory workability, strength, and durability simultaneously remains challenging. A multi-parameter mix-design methodology is proposed for solid-waste-based self-compacting concrete (SCC). This method couples minimum water demand, control of paste film thickness, and multi-performance balancing. The ternary solid-waste powder system (silica fume, fly ash, and supersulfated solid-waste-based cement) was first optimized through minimizing water demand to achieve maximum packing density. The resulting composition was then blended with varying dosages of ordinary Portland cement (OPC) to form the final cementitious binder. Aggregate gradation was proportioned to minimize voids, and paste volume was determined using an equivalent-paste-film-thickness model. Under comparable mixture conditions, SCC with OPC contents of 70–40 wt.% and paste film thicknesses of 2.0–2.6 mm was evaluated for fresh performance, compressive strength, freeze–thaw resistance, and material cost. Mixtures with a paste film thickness of 2.4 or 2.6 mm satisfied the self-compactability criterion—the mix with 50 wt.% OPC and a paste film thickness of 2.4 mm showed the best overall performance balance, achieving higher 28 d strength than higher-OPC mixtures while improving freeze–thaw resistance and reducing cost. Results from TGA, XRD, ATR–FTIR, and SEM–EDS analyses indicated enhanced calcium hydroxide (CH) consumption, increased formation of C-(A)-S-H and ettringite, and a denser interfacial transition zone (ITZ), supporting the proposed multi-objective design approach. While the framework was validated for a specific ternary binder system, it provides a reproducible proportioning strategy applicable to a broader range of solid-waste-based concrete systems, with potential for extension to other waste streams and exposure conditions, thus supporting the development of more resource-efficient and environmentally sustainable concrete. Full article

The development of all-concrete liquefied natural gas (LNG) storage tanks is hindered by the susceptibility of conventional concrete to ultra-low temperature (ULT) cycling down to −70 °C. While redispersible polymer powder (RPP) and polypropylene (PP) fibers individually enhance performance, their combined effect in various mineral admixture systems remains unclear. This study investigates the synergy and selective compatibility in hybrid-modified concrete containing fly ash (FA), silica fume (SF), or slag (SG). Comprehensive assessments after 50 ULT cycles reveal that the efficacy of hybrid modification is intrinsically governed by the mineral admixture. Among all systems, the silica fume-based hybrid system (EPSF) exhibits the highest residual compressive strength (57.5 MPa), the lowest strength loss (6.7%), and the most balanced durability. Microstructural analysis reveals that this synergy arises from a dense matrix, continuous polymer network, and effective fiber bridging—achieved only when the mineral admixture enables uniform RPP distribution. In contrast, the FA system exhibits a strength–durability trade-off, with RPP localized at interfaces, while the SG system shows a polymer-activated hydration mechanism. Microstructural and nano-mechanical analyses confirm that RPP acts as a pore filler in cement, an interfacial modifier in FA, a cohesive network former in SF, and a hydration activator in SG. This work establishes that superior ULT resilience requires not merely additive modifications but a matrix-enabled synergy, providing a scientific basis for the rational design of cryogenic concrete. Full article

The production of cement is associated with significant CO₂ emissions, while the escalating volume of solid waste poses severe environmental challenges. To reduce the dependence on cement and fully utilize solid waste materials to address these challenges, this study prepared alkali-activated concrete by completely replacing cement with solid waste materials (slag, fly ash, and silica fume). Research was conducted on the optimization of material mix design and fiber reinforcement. From macro–micro perspectives and through advanced characterization methods (SEM, XRD, and TG), the action mechanism of activator concentration and precursor material content on alkali-activated concrete was revealed, as well as the influence law of glass fiber on material properties. Meanwhile, the optimal activator concentration, precursor material content and fiber content were determined. The results show that appropriately increasing the activator concentration and slag proportion can effectively promote the formation of cementitious products, thereby improving the mechanical properties of the material. However, excessive alkalinity will lead to an uncontrolled reaction and adverse effects. The addition of fibers significantly enhances the mechanical properties of the material, especially the flexural strength. When the fiber content is 1.8%, the flexural strength is increased by 45.16%. This work establishes a sustainable pathway for construction materials, while addressing industrial waste management and carbon neutrality goals. Full article

Fiber-reinforced cemented tailings backfill (FTB) has been widely adopted in underground mining operations as an effective solution for mitigating the brittleness of cemented tailings backfill (CTB) and ensuring compatibility with deep mining environments. Understanding the coupled effects of temperature and binder composition on the thermal–hydro–mechanical–chemical (THMC) behavior of FTB is essential for low-carbon mix design and practical application. To address this knowledge gap, this work presents a systematic investigation into the influences of curing temperature, binder type, and cement content on the rheological properties, compressive strength, and THMC-related parameters of FTB. The results demonstrate that elevated temperatures accelerate hydration, reducing flowability while significantly enhancing strength and pore structure refinement. Conversely, low temperatures preserve flowability but impede strength development. The incorporation of slag or fly ash as partial cement substitutes reduces rheological parameters; however, fly ash substitution tends to compromise ultimate strength. Multi-field performance monitoring further reveals the underlying coupling mechanisms among temperature evolution, hydration kinetics, matric suction, and mechanical strength development. Based on these insights, a low-carbon design strategy is proposed, emphasizing dynamic optimization of cement content according to ambient temperature. These findings offer a theoretical foundation for the sustainable proportioning and performance control of mine backfill materials. Full article

This study examines the utilisation of fly ash from the energy sector as a secondary raw material in cement composites, with the aim of improving sustainability while maintaining high mechanical performance. By partially replacing Portland cement with industrial by-products, the proposed approach supports resource efficiency and aligns cement composite production with circular economy principles. Three formulations were tested: a reference mix and mixes with 25% and 50% cement reduction. Compressive strength reached 41 MPa, confirming suitability for construction use. Chemical and textural properties were analysed using XRD, FTIR, TGA, and nitrogen adsorption (BET, BJH). The results showed structural modifications, including new crystalline phases and changes in porosity. XRD confirmed newly formed phases, while FTIR identified Si-O-Si and Al-O-Si bonds, indicating effective activation of fly ash. Reducing cement content increased surface area and mesoporosity, enhancing performance. The findings demonstrate that fly ash can serve as a sustainable substitute for Portland cement within a circular economy framework, supporting CO₂ emission reduction and resource conservation while enabling the production of durable and environmentally responsible cement composites. Full article

Construction and demolition activities generate over one-third of all waste produced within the European Union, with the largest fraction being mineral materials, and concrete representing up to 90% of this volume. In this context, the recycling of this type of waste is an important research topic with growing scientific and industrial relevance. While numerous studies have examined the influence of recycled concrete and other industrial waste on the technical performance of Portland cement-based composites, the antimicrobial resistance of these composites remains largely unexplored. Therefore, in this study we evaluate the effects of three different waste materials on the key properties of Portland cement mortar, as well as on its antimicrobial resistance; the investigated waste materials were fly ash (produced in thermal power plants), recycled concrete fines resulted from the mechanical processing of concrete waste generated in construction and demolition activities, as well as dried concrete slurry (a byproduct of concrete batching plants). The partial replacement of Portland cement with these concrete wastes slightly increased the mortar’s workability (up to 4.6%). However, it also led to an 11–12% reduction in compressive strength after 28 days of hardening. After 60 days of curing, the antimicrobial properties of these mortars were evaluated by assessing their effect on planktonic microbial growth and their anti-adherent capacity against the most common pathogenic strains (S. aureus, E. coli, P. aeruginosa, C. albicans, and C. parapsilosis). Antimicrobial assays were performed at two different concentrations of microbial suspensions, and the mortars exhibited significant antibiofilm properties against all strains, especially against E. coli. The study identified mortar formulations in which partial replacement of cement with construction, demolition, and industrial waste materials resulted in compressive strength and antimicrobial resistance comparable to those of conventional reference mortars. These findings highlight the potential to integrate recycled waste into Portland cement-based materials, supporting both structural integrity and microbial resistance and advancing sustainable construction practices. Full article

Fly ash is an effective supplementary cementitious material for reducing clinker consumption and carbon emissions, but its low early reactivity often results in delayed hydration and insufficient early-age strength. This study investigated the age-dependent role of graphene oxide (GO) in fly ash-blended cementitious materials by combining compressive strength testing with X-ray diffraction (XRD), thermogravimetric analysis (TG-DTG), ²⁹Si magic-angle spinning nuclear magnetic resonance (²⁹Si MAS NMR), and scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS). Fly ash replacement levels of 10%, 20%, and 30% were considered, and 0.07% GO was introduced to evaluate its effect at 3, 7, and 28 days. The results showed that fly ash reduced the 3-day compressive strength, whereas the strength differences became much smaller at 28 days. GO enhanced the compressive strength of all fly ash-blended mixtures. XRD and TG-DTG results showed that GO refined Ca(OH)₂ crystallization and reduced the retained CH content, indicating more effective CH utilization during hydration and pozzolanic reaction. At 28 days, the incorporation of 0.07% GO increased the compressive strength of the 30% fly ash mixture from 47.38 MPa to 56.58 MPa, while reducing the total CH content from 14.20% to 12.89%, indicating enhanced CH utilization and gel development. ²⁹Si MAS NMR further demonstrated that GO promoted a more mature and polymerized silicate gel structure, as evidenced by lower Q⁰ fractions, higher mean chain length, and higher proportions of more polymerized silicate species. SEM-EDS observations confirmed that GO led to a denser matrix, less dominant coarse CH, and lower Ca/Si and Ca/(Si + Al) ratios. Overall, GO improved the mechanical performance of fly ash-blended cementitious materials through coupled regulation of hydration products, silicate gel polymerization, and matrix densification. Full article

Food waste poses significant environmental, economic and public health challenges. The black soldier fly (Hermetia illucens) larvae (BSFL) represent a promising solution for organic waste valorisation, converting substrates into protein-rich biomass for animal feed and organic fertiliser. However, the use of food waste as an insect substrate remains prohibited in the European Union due to regulatory and safety concerns. This study evaluated the suitability of heterogeneous food waste for BSFL rearing under industrial conditions by comparing larval performance on a standard Gainesville diet (control) and a blend derived from local restaurant waste (test). The 14-day bioconversion assay assessed bioconversion rate (BCR), feed conversion ratio (FCR), survival rate, average growth rate, and nutritional composition. Compared with the control, the test group showed significantly improved (p < 0.001) BCR (18.34% vs. 11.02%), FCR (5.48 vs. 9.09 kg/kg), survival (69.29% vs. 51.30%), and growth (8.38 vs. 6.59 mg/day). Larvae reared on food waste also exhibited significantly higher protein (19.70% vs. 16.80%), fat (13.70% vs. 7.20%), ash (6.97% vs. 3.51%), carbohydrates (7.00% vs. 3.60%), and fibre (5.20% vs. 2.90%). Overall, heterogeneous food waste is a suitable substrate for BSFL, supporting agrifood sustainability; however, future research should focus on standardisation of these substrates. Full article

This study investigated the effects of water-to-binder ratio (W/B), fly ash content, pH value, and SO₄²⁻ concentration on the neutralization depth and compressive strength of fly ash concrete under acid rain erosion, as well as the influence of W/B, cement content, and fly ash content on the carbonation depth in a carbonation environment. The Grey correlation analysis method was employed to evaluate the relative significance of each factor. The results indicated that the neutralization depth increased with higher SO₄²⁻ concentration, W/B, and fly ash content, but decreased with elevated pH. The compressive strength declined with increases in W/B, fly ash content, and SO₄²⁻ concentration, and also decreased under lower pH conditions. Carbonation depth increased with greater W/B and fly ash content. Grey correlation analysis revealed that W/B exerted the greatest influence on neutralization depth in the initial stage of acid rain attack, while pH value was the most significant factor for compressive strength. At later stages, SO₄²⁻ concentration became the dominant factor for both. Fly ash content was the most significant factor affecting carbonation depth. Full article

Conventional cement-based foamed lightweight soil (FLS) faces cost and environmental challenges. This study develops a sustainable polyvinyl alcohol (PVA) fiber-reinforced solid waste-based FLS (PVA-SWFLS) by entirely replacing cement with a ternary system of red mud, granulated blast furnace slag, and fly ash. PVA fibers were incorporated to mitigate inherent brittleness and cracking. The effects of fiber content (0–0.9 vol%), length (3–15 mm), water–binder ratio (0.35–0.55), and wet density (550–950 kg/m³) on the fluidity and compressive strength were evaluated, along with analyses of microstructure and pore characteristics using scanning electron microscopy and mercury intrusion porosimetry. Findings reveal that fiber addition reduces flowability (up to 34.9%) but significantly bolsters compressive strength, depending on fiber content and length. For 0.3% and 0.5% contents, optimal fiber lengths of 12 mm and 9 mm were observed, respectively; the 28-day compressive strength reached a maximum of 2.97 MPa at the 0.3% content with 12 mm fibers. Beyond these optimal points, and particularly for higher contents (0.7–0.9%), strength decreased monotonically with increasing fiber length due to fiber agglomeration and reduced compactness. Furthermore, strength correlated positively with wet density and negatively with the water–binder ratio, while fluidity increased with both. The hierarchy of influence was identified as: fiber content > fiber length, and wet density > water–binder ratio, while all four parameters significantly governed fluidity. The stress–strain behavior under different parameter combinations was analyzed, and a parametric constitutive model was established to support practical applications. Full article

The development of eco-efficient construction materials requires optimisation strategies that reduce cement consumption, valorise industrial by-products, and enhance performance without increasing material demand. Clay–cement sealing suspensions used in geotechnical engineering offer significant sustainability potential due to their high mineral content and compatibility with supplementary cementitious materials such as siliceous fly ash. The early-age rheological properties are essential for the design of geotechnical sealing barriers, yet the influence of chemical additive sequencing on flow behaviour remains poorly understood. This study examines how the priority of sodium silicate addition—introduced either before cement and siliceous fly ash (the “Prior” series) or after them (the “After” series)—affects the flow curves, yield stress, thixotropy, and equilibrium shear stress of clay–cement–fly ash sealing suspensions. Ascending flow curves were fitted to the Casson, Herschel–Bulkley, and Ostwald–de Waele models, and a shear-rate-resolved thixotropic power density analysis was applied to decompose the hysteresis behaviour. The results demonstrate that the Prior series produces deflocculated colloidal clay networks with localised cementitious agglomerates, exhibiting lower shear stresses at low shear rates but markedly higher yield stress amplitudes and larger hysteresis loop areas. The After series yields more uniformly distributed nucleation–coagulation networks with smaller hysteresis loops and pronounced structural rebuilding at low shear rates during the ramp-down phase. These findings provide a physicochemical framework for tailoring the early-age rheology of clay–cement suspensions through controlled additive sequencing, with direct implications for pumpability, injectability, and post-placement structural recovery in geotechnical applications. Full article