•Waste concrete recycling materials (WCRMs) are used in SCC.•Workability and mechanical behaviors of SCC with WCRMs are investigated.•Substitution percentage of WCRMs in SCC is evaluated and ...recommended.
This paper evaluates the feasibility of preparing self-compacting concrete (SCC) by incorporating waste concrete recycling materials (WCRMs). Some or all of the natural materials were substituted with WCRMs, such as recycled coarse aggregate (RCA), recycled fine aggregate (RFA) and recycled powder (RP). Nine SCC mixtures were produced, including eight self-compacting recycled concrete mixes and one control mix without WCRMs. The SCC mixes were designed with four different RCA replacement rates (0%, 25%, 50% and 100%) along with a constant amount of RFA (10%) and varying percentages of RP (10% and 20%). The water/binder ratio was designed as 0.4 for all the SCC mixtures. The workability properties (e.g., flowability, viscosity and passing ability) and mechanical properties (e.g., compressive, splitting tensile and flexural strengths) of self-compacting recycled concrete were investigated. The findings indicate that the substitution ratio of WCRMs will affect the workability and mechanical behavior of SCC. This study demonstrates that the decline in the workability and mechanical behavior of self-compacting recycled concrete results from the cooperation of WCRMs. When natural materials are substituted and the amount of WCRMs is limited, the workability of self-compacting recycled concrete can satisfy the European standard EFNARC (2005). Meanwhile, this study also finds that the self-compacting recycled concrete can achieve acceptable mechanical performance when compared to the ordinary SCC without WCRMs.
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•Alkali-activated cements (AACs) based on construction wastes (CDW) are obtained.•High compressive strengths of up to 102MPa were obtained for AACs.•Blocks, pavers, roof tiles and ...tiles (building materials) were made from AACs.•The recycled of CDW through “Alkali activation technology” were demonstrate.
The goal of this study was to test the viability of using red clay brick waste (RCBW), concrete waste (CW) and glass waste (GW) to produce alkali-activated cements (AACs) that can be used to fabricate blocks, pavers, roof tiles and tiles. The alkaline activators used were solutions of either NaOH or NaOH and waterglass. Ordinary Portland cement (OPC) was mixed with RCBW and CW in proportions of up to 30% to create hybrid cements. The AACs obtained with the RCBW, the CW and the GW exhibited maximum compressive strengths (28days) of 102, 33 and 57MPa, respectively.
Urban mining is essential for continued natural resource extraction. The recovery of rare and precious metals （RPMs） from urban mines has attracted increasing attention from both academic and ...industrial sectors, because of the broad application and high price of RPMs, and their low content in natural ores. This study summarizes the distribution characteristics of various RPMs in urban mines, and the advantages and shortcomings of various technologies for RPM recovery from urban mines, including both conventional （pyrometallurgical, hydrometallurgical, and biometallurgical processing）, and emerging （electrochemical, supereritieal fluid, mechanochemical, and ionic liquids processing） technologies. Mechanical/physical technologies are commonly employed to separate RPMs from nonmetallic components in a pre-treatment process. A pyrometallurgical process is often used tbr RPM recovery, although the expensive equipment required has limited its use in small and medium-sized enterprises. Hydrometallurgical processing is effective and easy to operate, with high selectivity of target metals and high recovery efficiency of RPMs, compared to pyrometallurgy. Biometallurgy, though, has shown the most promise for leaching RPMs from urban mines, because of its low cost and environmental friendliness. Newly developed technologies electrochemical, supercritical fluid, ionic liquid, and mechanochemical have offered new choices and achieved some success in laboratory experiments, especially as efficient and environmentally friendly methods of recycling RPMs. With continuing advances in science and technology, more technologies will no doubt be developed in this field, and be able to contribute to the sustainability of RPM mining.
Manufacturers are increasingly taking positive actions to handle used products by adopting “recycling materials” (RM), “remanufacturing product” (RP) or the hybrid strategy combining with both RM and ...RP (RMP). Under each strategy, in addition to the optimal quantity and price of new product, manufacturers may also face important decisions on the optimal quantity and price of remanufactured product and (or) recycling materials. To address such challenging issues, we consider a manufacturer who sells a new product to consumers, and examine the optimal recovery strategy and associated decisions by developing three models, i.e., models without incorporating recovery strategy, with considering recovery strategy and both recovery strategy and government subsidy. We further explore the impacts of product quality and government subsidy on the optimal decisions. Our results show that, neither recovery strategy including not implementing recovery strategy is always superior to the others, which depends on cost savings from remanufacturing products and benefits of recycling materials. Interestingly, the manufacturer with a higher product quality prefers to choose RP but RM otherwise. Government subsidy increases the manufacturer’s profit under each recovery strategy. In general, government subsidy helps to increase consumer surplus but reduce environment impact. However, as government subsidy increases, the manufacturer may prefer to implement RMP rather than RP, which may result in less consumer surplus and more environmental impact. Therefore, a higher subsidy unexpectedly may lead to a lower social welfare. This suggests that, the government should design an appropriate and more practical subsidy policy to dispose used products.
Sustainability of metal recovery from E-waste Debnath, Biswajit; Chowdhury, Ranjana; Ghosh, Sadhan Kumar
Frontiers of environmental science & engineering,
12/2018, Letnik:
12, Številka:
6
Journal Article
Recenzirano
Metal recovery techniques from electronic waste reported in literature. Metal recovery processes followed in Industries from electronic waste. Sustainability analysis of metal recovery processes from ...electronic waste.
The issue of E-waste disposal is concerning all the stakeholders, from policymakers to the end users which have accelerated the research and development on environmentally sound disposal of E-waste. The recovery of metals (gold, tantalum, copper, iron etc.) from E-waste has become an important focus. The mechanical recycling, thermo-chemical processes like pyrolysis, pyro-, hydro- and bio- metallurgical processes can play important roles in the Metal Recovery from E-waste (MREW) technology. For the industrial application of the MREW technology, it is important to analyze the sustainability. In this paper, two case studies have been presented on E-waste recycling industries in India and China. Based on the literature data, an attempt has been made to assess qualitatively the overall sustainability of MREW technology considering the three pillars, i.e., environmental, economic and social. Two conceptual frameworks with (Option -2) and without (Option -1) pyrolysis for integrated MREW units have been developed and the generalized energy and environmental impact analysis has been made using the principles of LCA. The impacts of two options have been compared. Option 2 has been found to be more efficient and sustainable. It has been realized that climate change, fossil fuel depletion, water depletion, eutrophication, acidification, fresh and marine water ecotoxicity are possible impact categories. The recommendations based on the generalized assessment are in good agreement with the findings of previous researchers on individual steps of MREW unit. The findings of this paper are expected to be beneficial to researchers and stakeholders for research directions and decision making on MREW.
The rise in the awareness of climate change and the increasing environmental concerns has led to research in the areas of using the waste materials from Ready Mix Plants. This paper is an attempt to ...focus on the use of these wastes as using ready mix concrete plant waste aggregates obtained by crushing, and finding motorized assets of concretes complete by using many aggregates proportions with various proportions. Recycling materials is an efficient way to increase the life cycle of the material and contributes to environmental protection.
Study of Sound Absorbing Panels Used in Road Traffic Chiriac, Elena-Adelina; Bujoreanu, Carmen
Buletinul Institutului Politehnic din Iaşi. Secţia Construcţii de maşini/Buletinul Institutului Politehnic din Iaşi, Secţia Construcţii de maşini,
06/2023, Letnik:
69, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The noise pollution has a negative effect on the human body and in some situations, exposure to high levels of pollution can lead to serious health problems. Referring to current studies, we can see ...a high interest in finding solutions to reduce the effects of noise pollution, such as sound absorbing panels. The purpose of this paper is to present the current stage of development of sound absorbing panels and the absorption coefficient of the materials used. The article will provide information on different types of panels and materials used in their construction, as well as their mechanical properties. New discoveries in the field related to recyclable materials used in the construction of sound absorbing panels represent an additional point of interest, as the construction of such prototypes protects the environment. The use of waste in the construction process of sound absorbing panels can be considered sustainable a future method.
Currently, the inappropriate disposal of plastic materials, such as polyethylene terephthalate (PET) wastes, is a major environmental problem since it can cause serious damage to the environment and ...contribute to the proliferation of pathogenic microorganisms. To reduce this accumulation, PET-type bottles have been recycled, and also explored in other applications such as the development of membranes. Thus, this research aims to develop electrospun microfiber membranes from PET wastes and evaluate their use as an air filter media. The solution concentrations varied from 20 to 12% wt% of PET wastes, which caused a reduction of the average fiber diameter by 60% (from 3.25 µm to 1.27 µm). The electrospun filter membranes showed high mechanical resistance (4 MPa), adequate permeability (4.4 × 10
m
), high porosity (96%), and provided a high collection efficiency (about 100%) and low-pressure drop (212 Pa, whose face velocity was 4.8 cm/s) for the removal of viable aerosol nanoparticles. It can include bacteria, fungi, and also viruses, mainly SARS-CoV-2 (about 100 nm). Therefore, the developed electrospun membranes can be applied as indoor air filters, where extremely clean air is needed (e.g., hospitals, clean zones of pharmaceutical and food industry, aircraft, among others).
Cement production uses large quantities of natural resources and contributes to the release of CO2. In order to treat the environmental effects related to cement manufacturing, there is a need to ...improve alternative binders to make concrete. Accordingly, extensive study is ongoing into the utilization of cement replacements, using many waste materials and industrial. This paper introduces the results of experimental investigations upon the mortar study with the partial cement replacement. Fly ash, silica fume and glass powder were used as a partial replacement, and cement was replaced by 0%, 1%, 1.5%, 3% and 5% of each replacement by the weight. Compressive strength test was conducted upon specimens at the age of 7 and 28 days. Microstructural characteristic of the modified mortar was done through the scanning electron microscope (SEM) vision, and X-ray diffraction (XRD) analysis was carried out for mixes with different replacements. The tests results were compared with the control mix. The results manifested that all replacements present the development of strength; this improvement was less in the early ages and raised at the higher ages in comparison with the control specimens. Microstructural analysis showed the formation of hydration compounds in mortar paste for each replacement. This study concluded that the strength significantly improved by adding 5% of silica fume compared with fly ash and glass powder.
Climate change on Earth has been intensified after the industrial revolution, resulted from some factors such as an increase in ambient temperature, greenhouse gases of the atmosphere and ...environmental pollutants.Nowadays, sustainable solutions are developing to resolve this problem, and sustainable development, as one of these approaches is situated on the world’s top programs, in order to achieve the protection of the environment and natural resources, correct and efficient management and utilization of the basic, natural and financial resources and achieving an optimal consumption pattern. New forms and types of materials used in modern buildings such as eco-friendly materials have important effects on superiority of contemporary sustainable constructions. The eco-friendly materials were described in current study, while the dry wall was also investigated, which its use has increased dramatically due to the importance of speed in construction of buildings and pre-fabricated structures. Thus, the present study was designed to investigate the characteristics of dry wall and its effects on the environment. The production and consumption of dry wall evaluated based on LCA and how to recycle its waste was done according to WARM’s model. In the following, a residential building was studied and the simulation of traditional building and the building with dry wall was performed to evaluate the amount of carbon dioxide production and fuel consumption in both cases. The simulation was done in current situation and future conditions till the year 2100. The results of the research showed that, the use of dry wall in construction causes a reduction of about 60% in fuel consumption as well as a decline of 22.5% in carbon dioxide production. Considering the climate changes in future, simulation results showed that the range of variations in energy consumption and carbon dioxide production for a dry-built building would be very low in 2030, 2050 and 2100, while variations in energy consumption and the production of carbon dioxide were found to be remarkable for the traditional building in these years. In general, maintaining sustained conditions and a significant reduction in resource consumption in the next century, obtained by implementing a dry-built building suggests the importance of using these materials to achieve the principles of sustainable architecture.
•Eco-friendly materials and their advantages for using in buildings.•Effect of using drywall systems as an eco-friendly material on energy efficiency.•Effect of using drywall systems on CO2 production vs traditional materials.•Effect of using drywall systems on climate change vs effect of traditional materials.•All the outputs are the results of building energy simulation.
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