Cleaner Materials最新文献

In recent times, the continuous growth of construction and demolition (C&D) activities have resulted in increases in the utilization of natural resources as well as global C&D waste production. A major part of C&D waste produced is dumped in landfills worldwide although some countries have adopted good recycling and reuse facilities to generated C&D waste. Based on an extensive critical review of published literature on the topic including global C&D waste recycling statistics and composition of generated wastes, this paper identifies key physical, mechanical, and geotechnical characteristics of recycled C&D waste aggregates specific to use as pavement base or subbase materials. Recycled aggregates typically have sufficient CBR, abrasion resistance, compressive strength and resilient modulus in accordance with various road standard specifications, which enable their applications for pavement base and subbase layer construction. Recycled aggregates typically have higher water absorption and lower specific gravity values than virgin aggregates. Furthermore, this study evaluates the feasibility and effectiveness of recycled aggregates in pavement base and subbase layers based on the detailed laboratory investigations. Additionally, case studies involving large-volume utilization of recycled aggregates for field-scale pavement construction are presented facilitating the broader adoption of recycled materials in sustainable construction of road pavements. These studies document crucial insights into its real field performance in terms of strength, durability and longevity. Finally, authors have discussed the potential challenges, research gaps and future insights on the use of recycled aggregates in pavement construction. The use of recycled aggregates in pavement construction still has some barriers and challenges such as availability in bulk quantity especially at the field scale and absence of road standards for application, which require further research and practical developments to promote the sustainable use of these materials in the future.

Concrete manufacturing is highly resource-intensive and is a major source of greenhouse gas emission. Accelerating depletion of natural resources such as sand, which is the primary material for aggregate in concrete manufacture is a growing problem. At the same time, the disposal of vast volumes of non-biodegradable plastic waste poses a global environmental challenge. The incorporation of aggregates derived from municipal plastic waste to substitute for sand has the potential to help address both issues, while at the same time mitigating greenhouse gas emission. This study examines the potential of municipal polyethylene terephthalate (PET) plastic waste as a fine aggregate in concrete manufacturing. The primary focus was on PET aggregates with non-uniform and uniform shapes ranging in size from 2.36 to 4.75 mm. In the concrete mixtures, 0 %, 30 %, and 50 % of the fine natural aggregate by volume were replaced with fine PET aggregate with a water to cement ratio of 0.40. The obtained results showed a reduction in compressive and splitting tensile strength when compared to control specimens. However, replacing 30 % of fine natural aggregate with PET (both uniform and non-uniform shapes) significantly improved chloride resistance by 13 % and 12 %, respectively, while also enhancing the bond between cement paste and PET particles. This study characterizes the material properties of PET concrete, which represents a promising method for reusing municipal plastic waste and mitigating environmental concerns in concrete production.

Recycled coarse aggregate concrete enables the creation of environmentally friendly and cost-effective mixes. It helps address the disposal problem of demolition concrete waste, meeting demand while improving product functionality and reusability. The abundance of obsolete buildings in cemeteries contributes to Construction and Demolition waste. Recycled Concrete Aggregate (RCA) from demolished structures can be utilized as aggregates, albeit with concerns about its impact on compressive strength due to absorption issues. This review aimed to study and develop the different Artificial Intelligence (AI) model for the prediction of the compressive strength of concrete with varying RCA content and natural coarse aggregate content as input parameters while compressive strength as output parameter. The range of the input parameters is 0 % to 100 % while the range output parameter is 28 MPa to 70.3 MPa. Experimental data from literature articles used to train and validate the model development. Engineers and researchers can utilize these models to predict compressive strength by changing the input parameters. XGBoost Regression Model performed well with R² 0.93594 followed by Random Forest Model with R² 0.92766, and Gradient Boosting Model with R² 0.90616 respectively. Ridge Regression, Lasso Regression, and Linear Regression Models were not performed well in predicting the compressive strength of RCA concrete with R² 0.57657, 0.57558, 0.57675 respectively. ANN also performed significant in prediction of RCAC compressive strength with R² 0.8039. Future research could focus on optimizing the mechanical properties of concrete containing RCA using AI models. Furthermore, the study extends its analysis to explore the application of AI in predicting the strength of various types of concrete, highlighting the versatility and potential of AI-driven approaches in enhancing concrete mix design.

Soil erosion poses a significant challenge to environmental management, threatening ecosystem health and sustainable development. Urgent action is required to implement effective erosion control measures within comprehensive environmental management strategies. This study investigates the effectiveness of sand crusts induced by Na₂CO₃-activated materials in mitigating soil erosion during various rainfall and windstorm events. The study evaluates the erodibility of Na₂CO₃-activated crusts under varying wind speeds (30, 60, 90, and 120 km/h) and rainfall intensities (30, 60, 90, and 120 mm/h) across 1 to 15 events. Surface strength is measured using penetrometer tests, and the microstructure of the formed crusts is examined through X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and energy-dispersive X-ray spectroscopy (EDS). The results underscore the effectiveness of Na₂CO₃-activated crusts in erosion control, with treated soil showing significantly reduced erosion compared to untreated soil under both wind and rainfall conditions. Penetrometer tests revealed a significant increase in surface strength, and microstructural analysis identified the formation of albite, anorthite, and brucite crystals, as well as various forms of calcite and portlandite phases in the treated soil. This study endorses Na₂CO₃-activated materials as a superior method for mitigating wind and rainfall erosion, highlighting their remarkable efficacy, eco-friendly properties, abundance of raw materials, straightforward implementation, and cost-effectiveness.

In this research, a new type of natural fiber-rubber-cement (FRC) composite for roofing applications is presented. This composite was made with Portland cement, coated oil palm fibers, and modified waste tire rubber powders. The implementation of fiber coating and rubber modification methods has resulted in a more effective blending and binding of the fibers and rubber powders with the cement paste. This has notably improved the adhesion between the fibers and cement, as well as between the rubber powders and cement within the composite. The FRC composite demonstrated significantly lower water absorption and thermal conductivity, with reductions of 85% and 18%, respectively, compared to the fiber-cement (FC) composite lacking rubber powders. Additionally, the FRC composite exhibited improvements in flexural strength and noise reduction coefficient by 10% and 20%, respectively, in comparison to the FC composite. Thus, incorporating rubber powders can enhance the properties of the FC composite. Consequently, the FRC composite is proposed as a viable alternative roofing material suitable for use in energy-efficient buildings.

Recent advancements in the development of low-emission materials have become a global imperative to achieve net-zero emissions in efforts to limit the effects of climate change. The materials transition agenda not only aims to substitute emission-intensive materials but also incorporates emission reduction efforts into goods and applications. Natural fiber composites have received attention from both commercial and research communities because of their inherent eco-friendliness, lower cost, and lower energy consumption during processing than their synthetic counterparts. Additionally, rubber-reinforced polymer composites have generally shown promising results, particularly in resisting sudden deformation. Although studies combining waste rubber with natural fibers in polymer composites are nascent, with limited existing literature, this area demonstrates remarkable potential for the substitution of traditional synthetic composites. Therefore, this review outlines the recent developments in polymer composites incorporating the use of natural fibers and rubber in various forms. The use of rubber as a filler has been shown to enhance tensile strength and impact performance while enhancing the surface finish, however, conflicting studies were identified. Hybridizing waste rubber and natural fibers presents a promising path to further enhance the mechanical performance of composite materials. Emphasis has been placed on the use of fillers in various forms and on their inclusion in thermoset matrices. The future outlook and research opportunities are also presented in this review.

Today, the biggest challenge faced by the refining industries globally is the production of environmentally friendly fuels with a high amount produced annually to meet the needs of markets due to the sharp regulations imposed environmentally with allowable sulfur levels in diesel fuel. This study examines the most recent developments in solid sorbent adsorption and catalytic oxidization techniques for desulfurizing diesel fuel. Reviewing the benefits, limitations, and future potential of each technique for desulfurizing liquid fuels using solid catalysts constructed using waste from agriculture. Activated carbon is one of these carbon materials; however, the traditional methods of producing activated carbon are time-consuming and costly. Activated carbon has impressive characteristics such as low concentration of ash, enormous surface area, permeability, ease of being activated, and high compressive strength, thereby rendering this an ideal substrate for the synthetic production of heterogeneous catalysts. Because they are in charge of igniting the substances that oxidize, their supported catalysts are crucial to the oxidation process. Various types of homogeneous and heterogeneous catalysts such as metal oxides, ionic liquids, polyoxometalates, and organic acids have been used to form oxidative desulfurization (ODS) systems. Therefore, to enhance the efficiency of catalytic ODS process some modifications must be taken into account. These adjustments may involve doping the catalyst’s surfaces with metal oxides or increasing the catalyst’s surface area when combined with sulfur compounds. In addition to reviewing the preparation conditions for carbon waste-based activated carbon catalysts, this work also carried out the desulfurization procedures to remove substances containing sulfur. Overall, the comprehensive review of carbon wastes into activated carbon catalysts with conventional and microwave heating shows promises in addressing two pressing environmental issues: agriculture waste management and reducing the ODS cost through the production of a sustainable fuel-efficient catalyst. This review explores the environmental feasibility of agro-waste as a waste-to-energy (solid carbon) technology. The use of agro-waste as a source to produce activated carbon catalysts mitigates the environmental impact associated with traditional waste disposal avenues, such as incineration and landfilling.

Concrete is a widely used construction material with notable environmental challenges. One primary concern is its reliance on nonrenewable resources. Additionally, the production of cement, its key ingredient, results in significant carbon emissions. To address these issues, the industry is increasingly considering geopolymer. This alternative stands out due to their sustainable nature and innovative use. Geopolymer effectively consume inorganic waste by utilizing it as one of its ingredients. This approach reduces the need for traditional waste disposal, as geopolymer is also applicable as construction materials. It also confronts the challenges of limited landfill space and the increasing disposal costs. However, there is a challenge in using raw, untreated waste for geopolymer production. These materials often require further processing to ensure their compatibility. This review explores into the potential of using various inorganic waste like fly ash, slag, rice husk ash, palm oil ashes as source material for geopolymer synthesis. Additionally, this paper also explores the potential of petroleum sludge, as one of the least utilized waste materials. Examination of its treatment, disposal techniques, and impact on the geopolymer matrix were reviewed and included in this paper. Overall, the findings highlight the benefits of leveraging waste materials. Another significant advantage is the availability of various source materials for geopolymer production, many of which are sourced from industrial, agricultural, and municipal waste streams, thereby promoting waste recycling, and reducing environmental impacts.

Geopolymer concrete emerges as a sustainable and durable alternative to conventional concrete, addressing its high carbon footprint and enhanced durability. The distinct properties of geopolymer concrete, governed by supplementary cementitious materials and alkaline activators, promise reduced environmental impact and improved structural resilience. However, its complex composition complicates the prediction of mechanical properties such as the elastic modulus, crucial for structural applications. This study introduces an innovative approach using the eXtreme Gradient Boosting (XGBoost) technique integrated with the multi-objective grey wolf optimizer to model the elastic modulus of geopolymer concrete. By dynamically selecting influential features and optimizing model accuracy, this methodology advances beyond traditional empirical models, which fail to capture the nonlinear interactions intrinsic to geopolymer concrete. Utilizing a comprehensive database gathered from extensive literature, 22 potential variables were examined that influence geopolymer concrete’s elastic modulus. After mitigating multicollinearity and optimizing hyperparameters via Bayesian optimization, six XGBoost models were developed with different combinations of input variables, revealing compressive strength and total water content as pivotal predictors. The findings illustrate the models’ precision, with the trade-off between prediction accuracy and model simplicity visualized through the relationship between the number of input variables and prediction error. The study culminates in a user-friendly graphical user interface that enables easy prediction of geopolymer concrete’s elastic modulus and fosters educational engagement. This interface, available online, underscores the practicality and accessibility of advanced machine learning predictions. Overall, this research not only provides a robust predictive framework for geopolymer concrete’s elastic modulus using optimized input variables but also enhances the understanding of its underlying determinants, contributing to the advancement of sustainable construction materials.

The direct manufacturing of rubber products from natural rubber latex through 3D printing, particularly extrusion in air, faces challenges in creating intricate shapes. Research suggests that utilizing 3D printing with extrusion in a support medium, known as direct ink writing (DIW), is effective for crafting complex-shaped rubber products. However, few studies have explored 3D printing natural rubber as a support medium. This study focuses on formulating a support medium for the DIW printing of natural rubber by incorporating triethanolamine (TEA) and alcohol in varying proportions. Key characteristics, such as viscosity, were assessed for each formulation, along with essential printing parameters, such as speed and flow rate. A suitable support liquid consisting of TEA (2.5 g), alcohol (160 g), Carbopol (1.5 g), and water (200 g) was determined for DIW printing natural rubber. The optimal settings were determined to be a nozzle size of 0.85 mm, a speed of 30 mm/s, and a flow rate of 30 mm³/s. Comparative results from the forming process indicate that 3D-printed rubber specimens exhibit poorer mechanical properties than traditionally molded specimens, owing to material uniformity. The vulcanized rubber system with the EV pattern exhibited superior mechanical characteristics. The developed support medium for DIW printing shows potential for use in intricate natural rubber products; however, further exploration of additional parameters is crucial for advancing complex-shaped natural rubber manufacturing using 3D printers.