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Search Results (337)

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Keywords = by-product aggregate

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37 pages, 3618 KiB  
Review
Lithium Slag as a Supplementary Cementitious Material for Sustainable Concrete: A Review
by Sajad Razzazan, Nuha S. Mashaan and Themelina Paraskeva
Materials 2025, 18(15), 3641; https://doi.org/10.3390/ma18153641 (registering DOI) - 2 Aug 2025
Abstract
The global cement industry remains a significant contributor to carbon dioxide (CO2) emissions, prompting substantial research efforts toward sustainable construction materials. Lithium slag (LS), a by-product of lithium extraction, has attracted attention as a supplementary cementitious material (SCM). This review synthesizes [...] Read more.
The global cement industry remains a significant contributor to carbon dioxide (CO2) emissions, prompting substantial research efforts toward sustainable construction materials. Lithium slag (LS), a by-product of lithium extraction, has attracted attention as a supplementary cementitious material (SCM). This review synthesizes experimental findings on LS replacement levels, fresh-state behavior, mechanical performance (compressive, tensile, and flexural strengths), time-dependent deformation (shrinkage and creep), and durability (sulfate, acid, abrasion, and thermal) of LS-modified concretes. Statistical analysis identifies an optimal LS dosage of 20–30% (average 24%) for maximizing compressive strength and long-term durability, with 40% as a practical upper limit for tensile and flexural performance. Fresh-state tests show that workability losses at high LS content can be mitigated via superplasticizers. Drying shrinkage and creep strains decrease in a dose-dependent manner with up to 30% LS. High-volume (40%) LS blends achieve up to an 18% gain in 180-day compressive strength and >30% reduction in permeability metrics. Under elevated temperatures, 20% LS mixes retain up to 50% more residual strength than controls. In advanced systems—autoclaved aerated concrete (AAC), one-part geopolymers, and recycled aggregate composites—LS further enhances both microstructural densification and durability. In particular, LS emerges as a versatile SCM that optimizes mechanical and durability performance, supports material circularity, and reduces the carbon footprint. Full article
26 pages, 4775 KiB  
Article
Effects of Partial Replacement of Cement with Fly Ash on the Mechanical Properties of Fiber-Reinforced Rubberized Concrete Containing Waste Tyre Rubber and Macro-Synthetic Fibers
by Mizan Ahmed, Nusrat Jahan Mim, Wahidul Biswas, Faiz Shaikh, Xihong Zhang and Vipulkumar Ishvarbhai Patel
Buildings 2025, 15(15), 2685; https://doi.org/10.3390/buildings15152685 - 30 Jul 2025
Viewed by 143
Abstract
This study investigates the impact of partially replacing cement with fly ash (FA) on the mechanical performance of fiber-reinforced rubberized concrete (FRRC) incorporating waste tyre rubber and recycled macro-synthetic fibers (MSF). FRRC mixtures were prepared with varying fly ash replacement levels (0%, 25%, [...] Read more.
This study investigates the impact of partially replacing cement with fly ash (FA) on the mechanical performance of fiber-reinforced rubberized concrete (FRRC) incorporating waste tyre rubber and recycled macro-synthetic fibers (MSF). FRRC mixtures were prepared with varying fly ash replacement levels (0%, 25%, and 50%), rubber aggregate contents (0%, 10%, and 20% by volume of fine aggregate), and macro-synthetic fiber dosages (0% to 1% by total volume). The fresh properties were evaluated through slump tests, while hardened properties including compressive strength, splitting tensile strength, and flexural strength were systematically assessed. Results demonstrated that fly ash substitution up to 25% improved the interfacial bonding between rubber particles, fibers, and the cementitious matrix, leading to enhanced tensile and flexural performance without significantly compromising compressive strength. However, at 50% replacement, strength reductions were more pronounced due to slower pozzolanic reactions and reduced cement content. The inclusion of MSF effectively mitigated strength loss induced by rubber aggregates, improving post-cracking behavior and toughness. Overall, an optimal balance was achieved at 25% fly ash replacement combined with 10% rubber and 0.5% fiber content, producing a more sustainable composite with favorable mechanical properties while reducing carbon and ecological footprints. These findings highlight the potential of integrating industrial by-products and waste materials to develop eco-friendly, high-performance FRRC for structural applications, supporting circular economy principles and reducing the carbon footprint of concrete infrastructure. Full article
(This article belongs to the Topic Sustainable Building Development and Promotion)
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15 pages, 2001 KiB  
Article
Study on the Impact of Lithium Slag as an Alternative to Washed Sand on Mortar Properties
by Xianliang Zhou, Wei Dai, Xi Zhu and Xiaojun Zhou
Materials 2025, 18(15), 3490; https://doi.org/10.3390/ma18153490 - 25 Jul 2025
Viewed by 212
Abstract
Lithium slag (LS), a by-product of lithium extraction processes, poses a significant disposal challenge during the rapid development of new energy technologies. In this study, LS was used to replace partially washed sand in the process of mortar production to compensate for the [...] Read more.
Lithium slag (LS), a by-product of lithium extraction processes, poses a significant disposal challenge during the rapid development of new energy technologies. In this study, LS was used to replace partially washed sand in the process of mortar production to compensate for the content of stone powder in sand. Five mortar mixes containing varying proportions of LS were prepared, and the macroscopic performance was evaluated. A comprehensive microscopic analysis, including microstructure observations, hydration product identification, and pore structure analysis, was conducted. The impact of LS on the chloride ion permeability of mortar was also investigated in this study. The results indicate that an increase in LS content gradually reduces the workability of the mortar, with a 39.29% decrease in fluidity when 40% of the sand is replaced with LS. Moreover, the compressive and flexural strengths of the mortar initially increase and then decrease with higher LS content. Microscopic tests reveal that 20% LS substitution significantly optimizes the pore structure of the mortar, resulting in a lower chloride ion permeability coefficient. Consequently, 20% LS substitution is recommended as the optimal dosage for use as fine aggregate in mortar. Full article
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18 pages, 3231 KiB  
Article
Investigation into the Properties of Alkali-Activated Fiber-Reinforced Slabs, Produced with Marginal By-Products and Recycled Plastic Aggregates
by Fotini Kesikidou, Kyriakos Koktsidis and Eleftherios K. Anastasiou
Constr. Mater. 2025, 5(3), 48; https://doi.org/10.3390/constrmater5030048 - 24 Jul 2025
Viewed by 175
Abstract
Alkali-activated building materials have attracted the interest of many researchers due to their low cost and eco-efficiency. Different binders with different chemical compositions can be used for their production, so the reaction mechanism can become complex and the results of studies can vary [...] Read more.
Alkali-activated building materials have attracted the interest of many researchers due to their low cost and eco-efficiency. Different binders with different chemical compositions can be used for their production, so the reaction mechanism can become complex and the results of studies can vary widely. In this work, several alkali-activated mortars based on marginal by-products as binders, such as high calcium fly ash and ladle furnace slag, are investigated. Their mechanical (flexural and compressive strength, ultrasonic pulse velocity, and modulus of elasticity) and physical (porosity, absorption, specific gravity, and pH) properties were determined. After evaluating the mechanical performance of the mortars, the optimum mixture containing fly ash, which reached 15 MPa under compression at 90 days, was selected for the production of precast compressed slabs. Steel or glass fibers were also incorporated to improve their ductility. To reduce the density of the slabs, 60% of the siliceous sand aggregate was also replaced with recycled polyethylene terephthalate (PET) plastic aggregate. The homogeneity, density, porosity, and capillary absorption of the slabs were measured, as well as their flexural strength and fracture energy. The results showed that alkali activation can be used to improve the mechanical properties of weak secondary binders such as ladle furnace slag and hydrated fly ash. The incorporation of recycled PET aggregates produced slabs that could be classified as lightweight, with similar porosity and capillary absorption values, and over 65% achieved strength compared to the normal weight slabs. Full article
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16 pages, 2206 KiB  
Article
Turning Waste into Wealth: Sustainable Amorphous Silica from Moroccan Oil Shale Ash
by Anas Krime, Sanaâ Saoiabi, Mouhaydine Tlemcani, Ahmed Saoiabi, Elisabete P. Carreiro and Manuela Ribeiro Carrott
Recycling 2025, 10(4), 143; https://doi.org/10.3390/recycling10040143 - 20 Jul 2025
Viewed by 266
Abstract
Moroccan oil shale ash (MOSA) represents an underutilized industrial by-product, particularly in the Rif region, where its high mineral content has often led to its neglect in value-added applications. This study highlights the successful conversion of MOSA into amorphous mesoporous silica (AS-Si) using [...] Read more.
Moroccan oil shale ash (MOSA) represents an underutilized industrial by-product, particularly in the Rif region, where its high mineral content has often led to its neglect in value-added applications. This study highlights the successful conversion of MOSA into amorphous mesoporous silica (AS-Si) using a sol–gel process assisted by polyethylene glycol (PEG-6000) as a soft template. The resulting AS-Si material was extensively characterized to confirm its potential for environmental remediation. FTIR analysis revealed characteristic vibrational bands corresponding to Si–OH and Si–O–Si bonds, while XRD confirmed its amorphous nature with a broad diffraction peak at 2θ ≈ 22.5°. SEM imaging revealed a highly porous, sponge-like morphology composed of aggregated nanoscale particles, consistent with the nitrogen adsorption–desorption isotherm. The material exhibited a specific surface area of 68 m2/g, a maximum in the pore size distribution at a pore diameter of 2.4 nm, and a cumulative pore volume of 0.11 cm3/g for pores up to 78 nm. DLS analysis indicated an average hydrodynamic diameter of 779 nm with moderate polydispersity (PDI = 0.48), while a zeta potential of –34.10 mV confirmed good colloidal stability. Furthermore, thermogravimetric analysis (TGA) and DSC suggested the thermal stability of our amorphous silica. The adsorption performance of AS-Si was evaluated using methylene blue (MB) and ciprofloxacin (Cipro) as model pollutants. Kinetic data were best fitted by the pseudo-second-order model, while isotherm studies favored the Langmuir model, suggesting monolayer adsorption. AS-Si could be used four times for the removal of MB and Cipro. These results collectively demonstrate that AS-Si is a promising, low-cost, and sustainable adsorbent derived from Moroccan oil shale ash for the effective removal of organic contaminants from aqueous media. Full article
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26 pages, 10465 KiB  
Article
Potential Use of Wastewater Treatment Plant Washed Mineral Waste as Flood Embankment Materials
by Jacek Kostrzewa, Łukasz Kaczmarek, Jan Bogacki, Agnieszka Dąbska, Małgorzata Wojtkowska and Paweł Popielski
Materials 2025, 18(14), 3384; https://doi.org/10.3390/ma18143384 - 18 Jul 2025
Viewed by 331
Abstract
Recycling washed mineral waste, generated as a byproduct of the mechanical wastewater treatment process, can be a beneficial alternative to widely used natural sand in construction. Studies on material from the Warsaw agglomeration, available in quantities sufficient for construction applications, demonstrated its high [...] Read more.
Recycling washed mineral waste, generated as a byproduct of the mechanical wastewater treatment process, can be a beneficial alternative to widely used natural sand in construction. Studies on material from the Warsaw agglomeration, available in quantities sufficient for construction applications, demonstrated its high usability in specific hydrotechnical applications. Key laboratory tests for material characterization included physical, permeability, mechanical, and chemical property analyses. The tested waste corresponds to uniformly graded medium sands (uniformity coefficient: 2.20) and weakly calcareous (calcium carbonate content: 2.25–3.29%) mineral soils with organic content ranging from 0.24% to 1.49%. The minimum heavy metal immobilization level reached 91.45%. At maximum dry density of the soil skeleton (1.78/1.79 g/cm3) and optimal moisture content (11.34/11.95%), the hydraulic conductivity reached 4.38/7.71 m/d. The mechanical parameters of washed mineral waste included internal friction angle (34.4/37.8°) and apparent cohesion (9.37/14.98 kPa). The values of the determined parameters are comparable to those of natural sands used as construction aggregates. As a result, washed mineral waste has a high potential for use as an alternative material to natural sand in the analyzed hydrotechnical applications, particularly for flood embankment construction, by applicable technical standards and construction guidelines. Full article
(This article belongs to the Section Construction and Building Materials)
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14 pages, 2816 KiB  
Article
A Colorimetric/Ratiometric Fluorescent Probe Based on Aggregation-Induced Emission Effect for Detecting Hypochlorous Acid in Real Samples and Bioimaging Applications
by Junliang Chen, Pingping Xiong, Huawei Niu, Weiwei Cao, Wenfen Zhang and Shusheng Zhang
Foods 2025, 14(14), 2491; https://doi.org/10.3390/foods14142491 - 16 Jul 2025
Viewed by 296
Abstract
Hypochlorous acid (HClO) serves as a biological mediator and is widely utilized as a disinfectant in food processing and water treatment. However, excessive HClO residues in food and environmental water raise concerns due to the potential formation of carcinogenic chlorinated byproducts and disinfection [...] Read more.
Hypochlorous acid (HClO) serves as a biological mediator and is widely utilized as a disinfectant in food processing and water treatment. However, excessive HClO residues in food and environmental water raise concerns due to the potential formation of carcinogenic chlorinated byproducts and disinfection byproducts (DBPs). Despite its importance, traditional methods for HClO detection often involve complex sample preparation, sophisticated instrumentation, and skilled operators. Herein, we report an aggregation-induced emission (AIE) small molecule fluorescent probe (NYV) that integrates colorimetric and ratiometric fluorescence responses for the detection of HClO. This probe exhibits high sensitivity, with a detection limit of 0.35 μM, a rapid response time of 1 min, and a wide linear range (0–142.5 μM), along with anti-interference capabilities, making it suitable for real-time monitoring. Furthermore, we have developed a portable solid-state sensor based on probe NYV for the rapid visual detection of HClO. The potential applications of this probe in real sample analysis and bioimaging experiments are demonstrated. Our findings contribute to the development of innovative fluorescent probes for HClO detection, with broad applications in food safety, environmental monitoring, and biomedical research on oxidative stress and ferroptosis. Full article
(This article belongs to the Section Food Analytical Methods)
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18 pages, 2954 KiB  
Article
Characterization of Carboxylated Cellulose Nanocrystals Isolated Through Oxalic Acid Hydrolysis from Solid Residues of Softwood-Derived Glycol Lignin Production
by Thi Thi Nge and Tatsuhiko Yamada
Molecules 2025, 30(14), 2922; https://doi.org/10.3390/molecules30142922 - 10 Jul 2025
Viewed by 317
Abstract
The efficient use of renewable lignocellulosic biomass has attracted wide interest, as it promises to reduce the environmental impact of fossil fuel consumption. A recently developed batch-scale process, which produces glycol lignin (GL) from softwood biomass, generates a considerable amount of cellulose-rich solid [...] Read more.
The efficient use of renewable lignocellulosic biomass has attracted wide interest, as it promises to reduce the environmental impact of fossil fuel consumption. A recently developed batch-scale process, which produces glycol lignin (GL) from softwood biomass, generates a considerable amount of cellulose-rich solid residues (SRs) as a byproduct. In this study, usable cellulose was isolated from SRs in the form of carboxylated cellulose nanocrystals (O-CNCs). The properties of O-CNCs were investigated to establish a possible integrated biomass utilization system based on the GL production technology. Three different forms of purified SRs—never-dried (N-Cel), freeze-dried (F-Cel), and vacuum-dried (V-Cel) cellulose—were subjected to oxalic acid (OA) hydrolysis at 95 °C for 4 h. The average length of O-CNCs ranged from 90 to 120 nm and the height ranged from 3 to 6 nm for separate particles and from 8 to 20 nm for aggregates. The carboxyl group content was 0.11–0.23 mmol/g O-CNCs. The overall results indicated that the yields, dimensions, surface charges, and thermal stability of the O-CNCs were largely influenced by the nature of the starting cellulose. In addition, O-CNCs prepared from recycled OA exhibited similar properties to those prepared from fresh OA. Full article
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17 pages, 3740 KiB  
Article
Experimental Study on the Activation Mechanism of Residual Slag Micro Powder After Recycled Aggregate of Waste Concrete
by Shengbo Zhou, Kai Zhang, Shengjie Liu, Li Gao, Jian Wang, Xiaojie Wang, Mengyao Cui and Lu Guo
Sustainability 2025, 17(13), 6046; https://doi.org/10.3390/su17136046 - 1 Jul 2025
Viewed by 382
Abstract
This study investigated sustainable activation strategies for residual slag micro powder derived from recycled waste concrete aggregates, aiming to advance circular economy principles in construction materials. An experimental study was carried out to explore the activation mechanisms of slag micro powder from recycled [...] Read more.
This study investigated sustainable activation strategies for residual slag micro powder derived from recycled waste concrete aggregates, aiming to advance circular economy principles in construction materials. An experimental study was carried out to explore the activation mechanisms of slag micro powder from recycled waste concrete aggregates to enhance its utility in building materials. Three methods—mechanical grinding, high-temperature calcination, and mechanical grinding–thermal activation—were evaluated comparatively. The results showed high-temperature calcination at 750 °C for 10 min proved most effective, achieving a 95.85% activity index. High-temperature calcination may contribute to the release of active SiO2 and Al2O3 substances of slag micro powder, thereby improving the hydration performance of slag micro powder and its cement mortar’s compressive strength. The flexural strength of cement mortar after different activation treatments was also analyzed. Mechanical grinding alone showed limited benefits, only achieving a less than 65.59% activity index, while the combined method negatively impacted the mechanical properties of cement mortar samples. An SEM (scanning electron microscope) and EDS (energy dispersive X-ray spectrometer) microstructural analysis supported these findings, highlighting enhanced hydration product formation after calcination at 750 °C for 10 min. This work may contribute to sustainable construction practices through the resource-efficient utilization of industrial by-products. Full article
(This article belongs to the Special Issue Sustainable Approaches for Developing Concrete and Mortar)
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15 pages, 3405 KiB  
Article
Influence of Al2O3 Additive on the Synthesis Kinetics of 1.13 nm Tobermorite, and Its Crystallinity and Morphology
by Raimundas Siauciunas, Liveta Steponaityte, Marius Dzvinka and Aivaras Kareiva
Materials 2025, 18(13), 3086; https://doi.org/10.3390/ma18133086 - 29 Jun 2025
Viewed by 358
Abstract
One of the effective types of heat-resistant insulating products with an operating temperature of 1050 °C is made from calcium silicates or their hydrates. These materials are made from synthetic xonotlite and 1.13 nm tobermorite. Various wastes and by-products from other industries can [...] Read more.
One of the effective types of heat-resistant insulating products with an operating temperature of 1050 °C is made from calcium silicates or their hydrates. These materials are made from synthetic xonotlite and 1.13 nm tobermorite. Various wastes and by-products from other industries can be used for the synthesis of the latter compound. However, such raw materials often contain various impurities, especially Al-containing compounds, which strongly influence the kinetics of 1.13 nm tobermorite formation and its properties. Using XRD, DSC, TG, and SEM/EDX methods, it was found that at the beginning of the hydrothermal synthesis, the Al2O3 additive promotes the formation of 1.13 nm tobermorite; however, it later begins to inhibit the recrystallization of semi-crystalline C-S-H(I)-type calcium silicate hydrate and pure, high-crystallinity 1.13 nm tobermorite is more easily formed in mixtures without the aluminum additive. Aluminum oxide also influence the morphology of 1.13 nm tobermorite. When hydrothermally curing the CaO–SiO2 mixture, long, thin fibers (needles) are formed within 24 h. Later, they thicken and form rectangular parallelepiped crystals. After adding alumina, the product produced by 24 h synthesis is dominated by agglomerates, the surface of which is partially covered with crystal plates. By extending the synthesis duration, amorphous aggregates are absent and the crystal shape becomes increasingly square. Full article
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26 pages, 5414 KiB  
Article
Microstructure and Mechanical Properties of Sustainable Concrete Incorporating Used Foundry Sand and Coal Bottom Ash
by Piotr Smarzewski
Sustainability 2025, 17(13), 5983; https://doi.org/10.3390/su17135983 - 29 Jun 2025
Viewed by 421
Abstract
This study investigates the potential for sustainable concrete production using industrial by-products: used foundry sand (UFS) and coal bottom ash (CBA). These materials were partially substituted for natural aggregates to reduce environmental impact and promote circular economy practices. UFS was used as a [...] Read more.
This study investigates the potential for sustainable concrete production using industrial by-products: used foundry sand (UFS) and coal bottom ash (CBA). These materials were partially substituted for natural aggregates to reduce environmental impact and promote circular economy practices. UFS was used as a replacement for fine aggregate, while both fine and coarse CBA were tested as substitutes for sand and gravel, respectively. The materials were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) to evaluate their mineralogical and microstructural properties. Six concrete mixtures were prepared with varying replacement levels (up to 70% total aggregate substitution) at a constant water-to-cement ratio of 0.50. Compressive strength tests were conducted at 28 days, supported by microstructural observations. Results showed that high levels of UFS and CBA led to reduced strength, mainly due to weak interfacial bonding and porous ash particles. However, moderate replacement levels (e.g., 20% fine CBA) maintained high strength with good structural integrity. The study concludes that both UFS and CBA can be used effectively in concrete when carefully dosed. The findings support the use of industrial waste in construction, provided that material properties are well understood and replacement levels are optimized. Full article
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25 pages, 1601 KiB  
Article
Effect of Steel Fibers on Shear Carrying Capacity of Rubberized Geopolymer Concrete Beams
by Divya S Nair and T Meena
Buildings 2025, 15(13), 2248; https://doi.org/10.3390/buildings15132248 - 26 Jun 2025
Viewed by 308
Abstract
Geopolymer concrete (GPC) offers reduced carbon emissions and employs industrial by-products such as fly ash and ground granulated blast furnace slag (GGBFS). In this study, the synergistic augmentation of shear carrying capacity in steel-fiber-reinforced rubberized geopolymer concrete (FRGC) incorporating industrial by-products such as [...] Read more.
Geopolymer concrete (GPC) offers reduced carbon emissions and employs industrial by-products such as fly ash and ground granulated blast furnace slag (GGBFS). In this study, the synergistic augmentation of shear carrying capacity in steel-fiber-reinforced rubberized geopolymer concrete (FRGC) incorporating industrial by-products such as fly ash, GGBFS, and recycled rubber for sustainable construction is investigated. The reinforced rubberized geopolymer concrete (RFRGC) mixtures contained 20% rubber crumbs as a partial replacement for fine aggregate, uniform binder, and alkaline activator. The findings revealed that 1.25% steel fiber achieved optimal hardened properties (compressive strength, flexural, and split tensile strength), with 12 M sodium hydroxide and oven curing achieving maximum values. An increase in molarity improved geopolymerization, with denser matrices, while oven curing boosted polymerization, enhancing the bonding between the matrix and the fiber. The effect of steel fiber on the shear carrying capacity of RFRGC beams without stirrups is also discussed in this paper. An increased fiber content led to an increased shear carrying capacity, characterized by an improvement in first crack load and a delayed ultimate failure. These results contribute to sustainable concrete technologies for specifically designed FRGC systems that can balance structural toughness, providing viable alternatives to traditional concrete without compromising strength capacity. Full article
(This article belongs to the Section Building Materials, and Repair & Renovation)
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17 pages, 6578 KiB  
Article
Research on the Influence Law and Mechanism of Regenerated Ceramic Tile Form and Replacement Rate on the Mechanical Properties of Ultra-High-Performance Concrete
by Xiuying Yang, Yiwu Xing, Zhen Wang, Shixin Duan, Guodong Zhao, Jie Song and Zhaohui Xiao
Materials 2025, 18(13), 3028; https://doi.org/10.3390/ma18133028 - 26 Jun 2025
Viewed by 346
Abstract
Ultra-high-performance concrete (UHPC) has gained widespread application across various domains owing to its superior properties. Nevertheless, the high cement content and associated costs present challenges, including significant shrinkage of the cement matrix and economic considerations. Using industrial by-products or waste to replace some [...] Read more.
Ultra-high-performance concrete (UHPC) has gained widespread application across various domains owing to its superior properties. Nevertheless, the high cement content and associated costs present challenges, including significant shrinkage of the cement matrix and economic considerations. Using industrial by-products or waste to replace some raw materials is one of the effective solutions. Meanwhile, China’s ceramic industry generates a large amount of waste every year. Applying ceramics in UHPC can effectively solve these problems. This study explores the use of recycled tile waste as a sustainable alternative to reduce the use of natural aggregates and cement and enhance the performance of UHPC. To investigate the impact of recycled ceramics on the mechanical properties of UHPC, three preparation methods were employed: (1) single incorporation of ceramic tile aggregate (CTA) to replace fine aggregates (0–100%), (2) single incorporation of ceramic tile powder (CTP) to replace cementitious materials (0–20%), and (3) dual incorporation of both CTA and CTP. The effects of different preparation methods and substitution rates on mechanical properties were evaluated through compressive and flexural strength tests, and microstructure analyses were conducted by scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP). The test results show that the compressive strength and flexural strength of UHPC increased with an increase in the ceramic particle substitution rate and reached the maximum value at a 100% substitution rate. On the contrary, ceramic powder substitution initially reduced the compressive strength, and it slightly recovered at a substitution rate of 10%. However, the bending strength decreased with an increase in the substitution rate of the ceramic powder. When ceramic particles and ceramic powder were used in combination, the compressive strength was the highest when 100% ceramic particles and 20% ceramic powder were used as substitutes. The maximum flexural strength occurred when 100% ceramic particles or 5% ceramic powder was used as a substitute. This study demonstrates that recycled ceramic waste can effectively enhance the mechanical properties of UHPC, providing a sustainable solution for reducing cement consumption and improving the performance of concrete. Full article
(This article belongs to the Section Construction and Building Materials)
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35 pages, 10135 KiB  
Article
Constitutive Model for Plain and Steel-Fibre-Reinforced Lightweight Aggregate Concrete Under Direct Tension and Pull-Out
by Hasanain K. Al-Naimi and Ali A. Abbas
Fibers 2025, 13(7), 84; https://doi.org/10.3390/fib13070084 - 23 Jun 2025
Viewed by 414
Abstract
In the present study, a programme of experimental investigations was carried out to examine the direct uniaxial tensile (and pull-out) behaviour of plain and fibre-reinforced lightweight aggregate concrete. The lightweight aggregates were recycled from fly ash waste, also known as Pulverised Fuel Ash [...] Read more.
In the present study, a programme of experimental investigations was carried out to examine the direct uniaxial tensile (and pull-out) behaviour of plain and fibre-reinforced lightweight aggregate concrete. The lightweight aggregates were recycled from fly ash waste, also known as Pulverised Fuel Ash (PFA), which is a by-product of coal-fired electricity power stations. Steel fibres were used with different aspect ratios and hooked ends with single, double and triple bends corresponding to 3D, 4D and 5D types of DRAMIX steel fibres, respectively. Key parameters such as the concrete compressive strength flck, fibre volume fraction Vf, number of bends nb, embedded length LE and inclination angle ϴf were considered. The fibres were added at volume fractions Vf of 1% and 2% to cover the practical range, and a direct tensile test was carried out using a purpose-built pull-out test developed as part of the present study. Thus, the tensile mechanical properties were established, and a generic constitutive tensile stress–crack width σ-ω model for both plain and fibrous lightweight concrete was created and validated against experimental data from the present study and from previous research found in the literature (including RILEM uniaxial tests) involving different types of lightweight aggregates, concrete strengths and steel fibres. It was concluded that the higher the number of bends nb and the higher the volume fraction Vf and concrete strength flck, the stronger the fibre–matrix interfacial bond and thus the more pronounced the enhancement provided by the fibres to the uniaxial tensile residual strength and ductility in the form of work and fracture energy. A fibre optimisation study was also carried out, and design recommendations are provided. Full article
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17 pages, 6242 KiB  
Article
Eco-Efficient Mortars with High-Content Construction, Waste-Derived Aggregates Functionalized via Nano-TiO2 for NOx Abatement
by Xiu-Cheng Zhang and Xue-Fei Chen
Processes 2025, 13(6), 1944; https://doi.org/10.3390/pr13061944 - 19 Jun 2025
Viewed by 279
Abstract
This study elucidates the photocatalytic NOx abatement efficacy of eco-efficient mortars incorporating construction waste-derived aggregates functionalized with nano-TiO2. The research findings demonstrate a positive correlation between NOx abatement efficiency and nano-TiO2 substitution ratio, with recycled glass sand (RG)-based panels exhibiting [...] Read more.
This study elucidates the photocatalytic NOx abatement efficacy of eco-efficient mortars incorporating construction waste-derived aggregates functionalized with nano-TiO2. The research findings demonstrate a positive correlation between NOx abatement efficiency and nano-TiO2 substitution ratio, with recycled glass sand (RG)-based panels exhibiting superior performance compared to standard sand and recycled clay brick sand (RCBS)-based counterparts. The employment of ultrasonic dispersion as a nano-TiO2 incorporation method yields enhanced abatement efficiency relative to direct mixing, attributable to improved photocatalyst dispersion and surface area accessibility. The loading capacity of nano-TiO2 on recycled aggregates is observed to be positively influenced by the concentration of nano-TiO2 solution, with recycled clay brick sand demonstrating the highest loading capacity. RG-RCBS panels are shown to exhibit higher NOx abatement efficiency than standard sand (SS)-RCBS panels, with an optimal substitution ratio of 40% glass sand identified for maximizing abatement efficacy in RG-RCBS systems. A decline in NOx abatement efficiency is observed with increasing NOx flow rate and concentration, attributable to reduced pollutant residence time and excess pollutant load exceeding the panels’ processing capacity. Prolonged curing time also results in diminished abatement efficiency, due to microstructural alterations within the mortar matrix and the accumulation of photocatalytic reaction byproducts. Collectively, these findings underscore the potential of recycled aggregate-based mortars, in conjunction with nano-TiO2, as a viable eco-efficient strategy for NOx abatement, highlighting the critical influence of material selection, photocatalyst loading, and operational parameters on system performance. Full article
(This article belongs to the Section Materials Processes)
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