Utilization Of Industrial Waste Research Articles

Lodo do Curtimento de couro em Argamassa: Valorização Sustentável

Purpose: This study aims to investigate the valorisation of sludge from Leather Tannery Wastewater Treatment Plants (LTWWTP) by incorporating it into cement mortars. Theoretical framework: The substantial quantity of waste generated by industries coupled with the scarcity of natural resources calls for the analysis, development, and implementation of treatment methods to recover and reuse materials, thereby minimising the environmental impact of waste disposal. The leather tanning industry, a significant polluter due to its use of hazardous and heavy materials, requires sustainable solutions for waste management. One promising approach is the incorporation of waste into cementitious matrices. Method: Three scenarios were examined: low-moisture sludge, ash obtained via incineration, and wet oxidation. Test specimens were prepared with varying proportions of cement replacement (0, 3, 5, 7, and 10%), and their flexural and compressive strengths were evaluated. Additionally, chemical analyses were conducted to assess solubility. Results and Conclusion: The results indicate that sludge can be used in small proportions without compromising the mechanical strength of the mortar. Substituting 10% cement with ash using the INC-2 incineration method improved mortar quality, exhibiting a higher compressive strength of 41 MPa and minimal water absorption (3.28%). Research implications: Drawing from these promising findings, it can be confidently asserted that utilising WWTP sludge in mortar is a practical, eco-conscious solution for civil construction. Furthermore, it is a pivotal step towards addressing the challenge of hazardous sludge disposal. Originality/value: The findings from this research will contribute to sustainable waste management practices and pave the way for responsible and eco-friendly utilisation of industrial waste in cementitious materials, thus minimising environmental burdens.

Preparation and alkali excitation mechanism of coal gangue-iron ore tailings non-sintering ceramsite

Non-sintering ceramsite is known for its simplicity in preparation technology and low production costs. The efficient utilization of industrial solid waste for non-sintering ceramsite production has garnered significant attention in green building materials within the framework of low carbon and environmental protection principles. This study focuses on preparing non-sintering ceramsites using non-active solid waste materials, specifically coal gangue and iron ore tailings. Firstly, a single-factor test was conducted to determine the optimal dosage of coal gangue and iron ore tailings. Subsequently, orthogonal tests were performed to investigate the influence of fly ash, NaOH, and aluminum powder on the mechanical properties of non-sintering ceramsite. Finally, the alkali excitation mechanism was elucidated through X-ray diffraction and SEM electron microscope scanning. The results reveal that the optimal proportions for coal gangue and iron ore tailings are 10 % and 35 %, respectively. Among the factors examined, NaOH dosage exerts the most significant impact on the compression strength and bulk density of non-sintering ceramsite, while aluminum powder dosage has the greatest effect on the 1-hour water absorption of the material. The optimal mixing ratio was determined with a total solid waste dosage of 73 %, meeting the national 600-grade standard for non-sintering ceramsite across all performance criteria. Furthermore, the alkali excitation process effectively activates the reactivity of fly ash and coal gangue. This activation leads to the generation of calcium alumina and C-S-H gel, along with other hydration products, which intertwine to form a dense gel structure. This structural enhancement further contributes to the improved performance of non-sintering ceramsite.

EDITORIAL NOTES: APPLICATION OF COMPUTATIONAL/ARTIFICIAL INTELLIGENCE IN CONCRETE STRUCTURES AND MATERIALS

In recent years, the application of computational/artificial intelligence (CI/AI) in concrete structures and materials has gained popularity as evident in the search in the SCOPUS database using these keywords. The integration of CI/AI in concrete structures marks a significant advancement in civil engineering, offering innovative solutions across various stages of infrastructure development. From analysis and design to construction, monitoring, and maintenance, CI/AI technologies revolutionize traditional practices, enabling engineers to optimize concrete structures for enhanced performance, durability, and sustainability. Material design and optimization in concrete have also been propelled forward by CI/AI technologies. Traditional methods rely on trial-and-error, but CI/AI models analyze vast datasets to identify optimal mixtures with superior properties and resistance to environmental factors. Utilization of supplementary cementitious materials and industrial wastes introduces complexities, addressed by CI/AI's predictive capabilities for short- and long-term concrete properties. By minimizing waste and energy consumption, CI/AI-driven design fosters environmentally friendly formulations while ensuring structural integrity. Overall, CI/AI enhances prediction, optimization, and monitoring, ushering in a new era of resilient and sustainable concrete materials. These advancements also contribute to sustainable development by optimizing material usage, reducing waste, and improving energy efficiency, underscoring CI/AI's transformative potential in shaping the future of concrete structures and materials.

Synthesis and Surface Strengthening Modification of Silica Aerogel from Fly Ash.

This study focuses on using activated fly ash to preparate silica aerogel by the acid solution-alkali leaching method and ambient pressure drying. Additionally, to improve the performance of silica aerogel, C6H16O3Si (KH-570) and CH3Si(CH3O)3 (MTMS) modifiers were used. Finally, this paper investigated the factors affecting the desilication rate of fly ash and analyzed the structure and performance of silica aerogel. The experimental results show that: (1) The factors affecting the desilication rate are ranked as follows: hydrochloric acid concentration > solid-liquid ratio > reaction temperature > reaction time. (2) KH-570 showed the best performance, and when the volume ratio of the silica solution to it was 10:1, the density of silica aerogel reached a minimum of 183 mg/cm3. (3) The optimal process conditions are a hydrochloric acid concentration of 20 wt%, a solid-liquid ratio of 1:4, a reaction time of two hours, and a reaction temperature of 100 °C. (4) The optimal performance parameters of silica aerogel were the thermal conductivity, specific surface area, pore volume, average pore size, and contact angle values, with 0.0421 W·(m·K)-1, 487.9 m2·g-1, 1.107 cm3·g-1, 9.075 nm, and 123°, respectively. This study not only achieves the high-value utilization of fly ash, but also facilitates the effective recovery and utilization of industrial waste.

The Role of Chemical Activation in Strengthening Iron Ore Tailings Supplementary Cementitious Materials

The preparation of iron ore tailings (IOTs) into supplementary cementitious materials (SCMs) is an effective approach to achieve value-added utilization of industrial solid waste. This study systematically investigates the hydration pattern and strength development of Portland cement systems with the incorporation of IOTs, steel slag (SS), granulated blast-furnace slag (GBFS), and fly ash (FA) under the action of different chemical additives. The hydration products, and microstructure and pore structure of the SCMs are analyzed using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and mercury intrusion porosimetry. The findings of this study demonstrate that chemical activation plays a significant role in the strength development of SCMs. Among the five chemical activators tested, Triethanolamine (TEA) had the greatest influence on mechanical properties. The maximum compressive strength of the SCMs at 28 days was 42.9 MPa at a dosage of 1%. Specifically, the addition of TEA promotes volcanic ash reactions, and the high fineness of SCM provides nucleation sites for hydration products. Interactions between the volcanic ash reaction and the complexation reaction of TEA have a positive effect on compressive strength development. This research expands the potential for IOTs SCMs through chemical activation methods for value-added applications.

Mechanical performance, impact behavior and environmental assessment of coal furnace slag based low-carbon ultra-high performance engineered cementitious composites (UHP-ECC)

This study aimed to optimize the utilization of industrial solid waste through developing a high-performance cement-based composite material (UHP-ECC), incorporating coal furnace slag (CFS) and waste rubber powder (RP). The investigation concentrated on the effects of introducing 10% RP into UHP-ECC and replacing ordinary Portland cement (OPC) with CFS at varying proportions (0%, 20%, 40%, 60%) on mechanical properties, impact resistance, and sustainability. The mixtures underwent a comprehensive characterization, including mechanical tests, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), to clarify hydration mechanisms and microstructural features. The results revealed that the addition of 10% rubber led to flaws, resulting in a minor reduction in compressive strength from 143.2 MPa to 132.2 MPa. Substituting 20% with CFS resulted in a denser matrix, raising the compressive strength to 135.5 MPa. CFS decreased the initial cracking strength and matrix fracture toughness, with tensile strain peaking at 8.05% and narrower crack widths. More CFS content yielded a slight decrease in peak impact force but induced more fine cracks and enhancing ductility. Moreover, as CFS is a waste product generated at high temperatures, the mixture demonstrated outstanding impact performance at 150 °C, absorbing rather than converting more energy into kinetic energy. Comparative analysis against similar mixtures highlighted UHP-ECC's strengths in embodied carbon, embodied energy, and material cost. The Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) assessment identified the CFS40-R10 as better mixture, achieving a balance between mechanical performance, cost-effectiveness, and sustainability. Microscopic analysis revealed that up to 40% CFS facilitated hydration, and the 60% CFS mixture exhibited the lowest total mass loss at high temperatures.

Investigating the impact of alkaline activator on the sustainability potential of geopolymer and alternative hybrid materials

Geopolymer binders are considered highly sustainable due to their utilization of industrial wastes. However, previous studies highlight the limited industrial-scale applications of geopolymers. Therefore, this study critically investigates the strength, cost, and environmental impact of geopolymers and alternative hybrid cement mixes to provide a complete picture for the sustainability analysis. Geopolymers and hybrid cement mixes are designed with varying proportions of alkaline activator (sodium hydroxide 5–25 wt%) and ordinary Portland cement (OPC) (15–35 wt%) respectively for the comparative analysis. The strength characteristics of designed mixes have been assessed by analyzing their compressive strength and microstructure. A comparative economic assessment has been made by contemplating the manufacturing and production costs of different materials used in geopolymer and hybrid cement mixes. ReCiPe Midpoint Life cycle assessment (LCA) has been performed to examine the environmental performance by considering the manufacturing and production processes of various binder and aggregate materials used in geopolymer and hybrid cement mixes. Mechanical and microstructural analysis shows that hybrid cement mix with 35 wt% of OPC yields the highest strength due to the formation of excess calcium aluminum silicate hydrate (C-A-S-H) and calcium silicate hydrate (C–S–H) gels than geopolymer mix containing 25 wt% of NaOH. Economic and life cycle assessment reveals that the geopolymer mix with 5 wt% NaOH offers the lowest cost and environmental impact as compared to others containing higher proportions of alkaline activator and OPC. Owing to the conflicting nature of the results, multi-criteria decision making approach has been used which presents the hybrid cement mix (with 35 wt% OPC) as the optimal and sustainable solution for the construction applications. The study's findings offer a sustainable direction for the construction industry by suggesting the application of hybrid concretes.

A detailed review study on utilization of mine and industrial wastes for backfill strengthening

A detailed review study on utilization of mine and industrial wastes for backfill strengthening

Waste to Resource: Surface Modification of Electric Arc Furnace Flue Dust by Ball Milling and In Situ Carbonization

In this article, instead of synthesizing the electrode active material using expensive precursors that lead to high carbon emissions to the atmosphere during fabrication, an alternative engineering approach is presented for the utilization of the electric arc furnace flue dust, which is an industrial waste, as anode material in lithium-ion batteries. In this scope, firstly ball milling of the flue dust with citric acid is applied and then in situ carbonization conditions are optimized by pyrolyzing the mixture at different temperatures (600 °C and 750 °C) and times (4 h and 6 h). Every sample delivers capacities greater than graphite. Structural, morphological, and chemical characterization results demonstrate that the designed method not only promotes the formation of a nanometer-thick carbon layer formation over the particles but also induces partial phase transformation in the structure. The best performance is achieved when citric acid is used as the carbon source and the ball-milled powder is treated at 600 °C for 4 h in nitrogen (C6004): It delivers 714 mAh g−1 capacity under a current load of 50 mA g−1 after 100 cycles. This research is expected to set an example for the utilization of different industrial wastes in high value-added applications, such as energy storage.Graphical

Micro-assessment of heavy metal immobilization within alkali-activated copper tailings-slag geopolymer

To address the challenge of mitigating heavy metal pollution stemming from the utilization of industrial solid wastes like copper tailings, this study focused on the development of copper tailings-granulated blast furnace slag (CT-GBFS) geopolymer through alkali activation. The primary objective was to effectively immobilize heavy metals, specifically copper (Cu) and zinc (Zn), within the geopolymer. This investigation encompassed an exploration of how Cu and Zn impacted the mechanical properties of CT-GBFS geopolymer, along with an analysis of the leaching behavior of these heavy metals in various environmental conditions. The study also delved into the underlying mechanisms responsible for immobilizing these heavy metals. The experimental findings revealed that the inclusion of up to 2% heavy metals could enhance the mechanical properties of geopolymer. However, as the heavy metal content increased, a detrimental effect on the mechanical properties became evident. Furthermore, CT-GBFS geopolymer exhibited excellent heavy metal immobilization capabilities across different environmental conditions. Specifically, the immobilization rate for copper exceeded 98%, while zinc exhibited an immobilization rate exceeding 93%. The geopolymer has a physical encapsulation fixation mechanism for both Cu and Zn. Additionally, copper was observed to form a covalent bond with non-bridging oxygen in the geopolymer, manifesting as a Si–O–Cu structure, thereby effectively immobilizing the metal. Conversely, zinc was immobilized within the geopolymer through ionic bonding. In conclusion, the technology proposed in this study represents a significant step toward achieving the safe and resourceful utilization of copper tailings by effectively immobilizing heavy metals, thus mitigating their environmental impact.

Microwave co-pyrolysis of industrial sludge and waste biomass: Product valorization and synergistic mechanisms

Microwave co-pyrolysis of textile dyeing sludge (TS) and furfural residue (FR) was investigated in this study. Comprehensive pyrolysis index (CPI) was employed to investigate pyrolysis performance and FR addition significantly improved co-pyrolysis. Product distribution showed that increasing FR ratio enhanced the bio-oil and gas with significant reduction in biochar. For bio-oil, FR addition neutralized the strong alkalinity and inhibited the formation of nitrogen compounds. Moreover, bio-oil maintained a very low oxygenates content (0.97–5.97%). For biochar, co-pyrolysis was favorable for the enrichment of C and H and mitigated the potential contamination. FR addition increased the calorific value and contributed to pore development of biochar. Online inspection displayed that co-pyrolysis drastically restrained the release of sulfur-compounds and nitrogenates in volatile, while enhanced the production of alkanes, aldehydes, and ketones. Moreover, the interaction between TS and FR was influenced by their major components. For heavy metals (HMs), Er was at low risk for most HMs and FR addition ratios of 40 and 80 wt% appeared to be more favorable. Principal component analysis (PCA) showed that FR addition changed the decomposition behavior and affected co-pyrolysis process. This study also evaluated the co-pyrolysis synergistic mechanisms of TS and FR. Overall, microwave co-pyrolysis is a novel and effective method to reduce environmental pollution and produce high-quality products, providing new insights for the low consumption and efficient utilization of industrial solid waste.

Feasibility of Preparing Steel Slag–Ground Granulated Blast Furnace Slag Cementitious Materials: Synergistic Hydration, Fresh, and Hardened Properties

Steel slag and GBFS are wastes generated during the steel and iron smelting process, characterized by their considerable production rates and extensive storage capacities. After grinding, they are often used as supplementary cementitious materials. However, the intrinsic slow hydration kinetics of steel slag–GBFS cementitious material (SGM) when exposed to a pure water environment result in prolonged setting times and diminished early-age strength development. The incorporation of modifiers such as gypsum, clinker, or alkaline activators can effectively improve the various properties of SGM. This comprehensive review delves into existing research on the utilization of SGM, examining their hydration mechanisms, workability, setting time, mechanical strengths, durability, and shrinkage. Critical parameters including the performance of base materials (water-to-cement ratio, fineness, and composition) and modifiers (type, alkali content, and dosage) are scrutinized to understand their effects on the final properties of the cementitious materials. The improvement mechanisms of various modifiers on properties are discussed. This promotes resource utilization of industrial solid wastes and provides theoretical support for the engineering application of SGM.

Influence of chlorine on co-processing of hazardous wastes in brick kilns

Brick kiln co-treatment is a novel industrial hazardous wastes (IHWs) utilization process. However, the effects of chlorine (Cl) in wastes on heavy metals (HMs) during this process are overlooked. This study investigated the stabilization/solidification (S/S) and volatilization, as well as long and short-term leaching, of HMs in Cl-containing bricks. The results indicated enhanced formations of stable mineral phases (NiFe2O4, Ni2SiO4, Cd3Al2Si3O12, CdSiO3, FeCr2O4, Cr2O3, CuFe2O4, and CuAl2O4) in bricks at a low sintering temperature (800 °C) due to the affinity between Cl and HMs. By comparing HM concentrations before and after sintering in bricks, the study observed that Cl's presence significantly elevated the volatilization rates for Cd and Cu by 30.8% and 14.2%, respectively. In contrast, the effect on volatilization for Ni and Cr was not significant. Additionally, utilizing the NEN 7375 method, the cumulative leaching rates of Ni, Cd, Cr, and Cu over a 64-day experiment under extremely acidic conditions were 0.22%, 7.18%, 0.01%, and 1.46%, respectively. Similarly, higher short-term leaching rates of Cd (4.03%) and Cu (5.73%) than those of Ni (0.94%) and Cr (0.08%) were observed. This finding might be attributed to the lower stability of the Cd and Cu solid phases under acidic environments compared to those of Ni and Cr. Surface wash-off, dissolution, and diffusion were the processes governing HM leaching from bricks. The 10-year projections revealed a minimal release of HMs during future extended leaching, implying the successful S/S of HMs. This study provides a reference for assessing the environmental impacts of brick kiln co-processing of Cl-containing IHWs.

A sustainable temperature-swing process for CO2 capture and mineralization at below 100 °C using a recyclable chelating agent and bottom ash

Industrial waste utilization for carbon dioxide (CO2) mineralization offers a highly promising approach to significantly reduce CO2 emissions; however, it faces the challenge of consumption of huge amounts of chemicals without their recovery. This study proposes an improved CO2 mineralization process that employs a highly recyclable solution of environmentally friendly chelating agent, N,N-Dicarboxymethyl glutamic acid (GLDA) enriched with NaHCO3 and involves the temperature swing-facilitated dissolution and carbonation of Ca-bearing industrial wastes under ambient pressure and low temperature (<100 °C). Using bottom ash collected from plastic incineration as a representative solid waste, this study emphasizes the significance of temperature control during the Ca extraction and carbonation processes. Ambient temperatures prove favorable for efficient Ca extraction from incinerator bottom ash, while a relatively higher temperature (95 °C) is recommended for subsequent Ca carbonation; the carbonation process was then self-promoted due to the pH increase from carbonation. Subsequently, the solution was efficiently regenerated after use for CO2 capture. Across five CO2 mineralization cycles using the same solution, a comparable CaCO3 generation efficiency was demonstrated, suggesting the high recyclability of the solvent and sustainability of this approach. Although heavy metal accumulation was observed in the extraction solution during cycling, it did not negatively affect the Ca extraction and heavy metal-free CaCO3 was successfully produced. Overall, the proposed CO2 mineralization process utilizing the recyclable GLDA solution has significant potential as a green technology crucial for the global pursuit of CO2 mitigation.

Pozzolanic performance and characteristic analysis of binary blended cement incorporating ceramic polishing sludge

The waste generated during ceramic polishing is typically disposed of in landfills rather than being recycled within the production facility, potentially causing environmental harm. This study aims to enhance industrial waste utilization and reduce CO2 emissions in the cement industry by investigating the feasibility of incorporating ceramic sludge from polishing processes into an innovative binary blended cement. Different binders were prepared with varying amounts of ceramic polishing sludge (CPS), ranging from 10% to 50%, and tested against the ASTM C595 standards. The results were compared with those of ordinary Portland cement (OPC). This approach involves evaluating the pozzolanic activity and conducting an advanced characterization assessment of CPS and binary blended ceramic polishing sludge cement (CPSC) paste. This study employed a combination of physical, mechanical, and chemical tests, including setting time, particle size distribution (PSD), Brunauer-Emmett-Teller (BET) specific surface area, compressive strength, X-ray diffraction (XRD), scanning electron microscopy (SEM), heat of hydration, and differential scanning calorimetry/thermogravimetric analysis (DSC/TGA). The results indicated that CPS can be used as a pozzolanic material to create innovative binders with properties comparable to those of OPC. The Strength Activity Index (SAI) values affirmed the pozzolanic properties of CPS, exceeding 75% for up to 40% CPS replacement. Incorporating CPS in the blended cement resulted in a slower rate of cement hydration, leading to prolonged setting times and reduced early strength development. Although the compressive strength decreased with increasing CPS content, it remained within the acceptable ASTM C595 limits with up to 50% replacement. Nevertheless, the optimal replacement level of OPC with CPS was determined to be 50%. Furthermore, CPS substitution reduced the dry density and improved the water absorption and apparent porosity, reflecting microstructural changes. The SEM images revealed that the blended CPSC had a lower apparent porosity than the pure OPC. The DSC/TGA analysis demonstrated that the blended cement had a lower calcium hydroxide content and higher silica than pure OPC.

Comparative Studies of Microstructural, Mechanical and Tribological behaviour of A319 alloy cast in solid waste mold and conventional sand Mold

Abstract This study investigates the potential of utilizing industrial solid waste (blast furnace slag, ferrochrome slag, and red mud) as mold materials to improve the solidification rate and wear resistance of A319 alloy. Unlike conventional molds such as silica sand and olivine sand, industrial solid waste poses an eco-friendly alternative, contributing to waste valorization. The motivation for this research drives the need for sustainable and efficient waste management practices in the industrial sector. By exploring the utilization of industrial solid waste as a mold material, study aims to address the current challenges in disposal, reduce environmental impact, and enhance the overall performance of A319 alloy through improved solidification and wear resistance. The experimental phase involved multi-factor reciprocating sliding wear tests conducted on a sample using a linear reciprocating tribometer, employing a steel ball as a counter face. The investigation of reciprocating wear characteristics aimed to assess the correlations between solidification rate and wear properties of a specimen cast in an industrial solid waste mold as well as a sand mold. Notably, tribological test results revealed a low wear rate of 3.3 mg/Km for the blast furnace slag mold. The scanning electron microscopy (SEM) image of the wear surface showed adhesive wear mechanisms. This study contributes valuable insights into the potential environmental and performance advantages of repurposing industrial solid waste for foundry applications.

Research Progress on the Performance of Aerated Concrete

Abstract: With continuous attention to energy-saving emission reduction and ecological protection, people gradually realize the excellent performance of aerated concrete in energy saving, material saving, industrial solid waste utilization and other aspects, and the research of aerated concrete pays more and more attention. Aerated concrete with its own lightweight, high strength, heat insulation, heat preservation and environmental protection advantages, has been widely promoted and applied in green buildings. This paper summarizes the green characteristics of aerated concrete and discusses the application prospect of aerated concrete.

Converting industrial waste into valuable Zn2SiO4/SiO2 nanosheets for highly effective organic dye removal

As a common industrial waste, fly ash is conventionally used as a concrete additive, resulting in the wastage of silicon and aluminium materials and environmental pollution. In this study, we innovatively utilize fly ash waste to synthesize Zn2SiO4/SiO2 nanosheets, which are employed as effective adsorbents for purifying organic dyes such as methylene blue, rhodamine B, and congo red. The Zn2SiO4/SiO2 nanosheets, with a large specific surface area of approximately 81.21 m2 g−1, exhibit enhanced adsorption capacity for organic dyes, in contrast to pure fly ash with a specific surface area of only ∼1.06 m2 g−1. Notably, the Zn2SiO4/SiO2 nanosheets demonstrate a remarkable adsorption capacity of 124.50 mg g−1 for methylene blue, which is ∼120 times higher than pure fly ash. The adsorption kinetics are analyzed using Langmuir and Freundlich models, shedding light on the adsorption mechanism of the Zn2SiO4/SiO2 adsorbent. This study presents an efficient ‘waste-to-treasure’ approach, advocating for the secondary utilization of industrial waste to alleviate environmental pollution.

Study on preparation and activation enhancement effect of cold bonded multi-solid waste wrap-shell lightweight aggregates (SWSLAs) with low cement content

Cement production consumes large amounts of depleted resources and energy, and causes environmental pollution. In order to reduce cement consumption and realize the closed-loop recycling of solid waste, cold bonded solid waste wrap-shell lightweight aggregates (SWSLAs) with a sextuplet blended system composed of dredged sediments, mineral powder, steel slag, phosphogypsum, fly ash, and a minimal amount of cement were prepared. Through the single-factor experiment, the influences of the types and dosages of solid wastes in the nuclear phase of SWSLAs (SWSLAs-NP) and shell phase of SWSLAs (SWSLAs-SP) on the strength and water resistance were explored, and the optimum ratio was obtained. On this basis, the influence of the types and amounts of activators incorporated in SWSLAs on the physical properties of aggregates was studied, and the primary microstructure of the aggregate was characterized. Our results showed that the optimal ratio of solid waste in the SWSLAs-NP was: 40 wt% of dredged sediments, 24 wt% of mineral powder, 18 wt% of steel slag, and 18 wt% of phosphogypsum. The optimal weight ratio of cement and solid waste in the SWSLAs-SP was 5:95. The resulting aggregate had a bearing capacity of single grain of 73.83 N and a water-resistance coefficient of 0.67. After the above aggregates were treated with Na2SO4 (activator) at 2%, the bearing capacity and water-resistance coefficient of the aggregates increased by 47.00% and 11.94%, respectively. The performances were even better than that of the aggregate composed of100w cement in the shell phase. Microstructural observations demonstrated that the structure of the raw material was reconstructed under the action of Na2SO4, and the raw materials reacted with each other, and thus the densification of the aggregate and its core-shell interface structure was enhanced, which improved the comprehensive performance of the aggregate. This study represents a step toward efficient utilization of industrial solid wastes.

Performance Analysis of Self-Compacting Concrete with Use of Artificial Aggregate and Partial Replacement of Cement by Fly Ash

Artificial aggregate (AF), i.e., silico manganese (SiMn) slag aggregate, is a byproduct of ferromanganese and silico manganese alloy production. The utilization of industrial waste and industrial byproducts in construction has increased the aim of conserving natural resources to nurture a pollution-free environment. The current study examines the performance of the use of artificial aggregate (AF) and partial replacement of cement with fly ash (FA). The properties of fresh concrete, as well as the compressive and flexural strength and split tensile strength of concrete were evaluated. Seven mix proportions were prepared for M30-grade concrete. The first was a control mix (with 0% AF and FA), three other mixes contained varying amounts of AF (20%, 40%, and 60%) as a partial replacement of CA with AF. The average compressive strength of the control SCC was found to be 32.87 MPa (megapascals) at the age of 28 days, and after replacing 20% natural aggregate with artificial aggregate, the compressive strength increased by 8.27%, whereas for 40% and 60% replacement, it decreased by 4.46% and 12.55%, respectively. Further investigation was performed on the optimum value obtained by replacing 20% of CA with AF. At this percentage, cement was replaced by FA at (15%, 25%, and 35%) where at 15%, the average compressive strength increased by 7.41%, whereas for 25% and 35% replacement, it decreased by 7.47% and 17.19%, respectively. For SCAF20 and SCF15, all strengths were at maximum due to the increase in its density. The findings show that the development of advanced construction materials is environmentally sustainable.