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Special Issue "Recycled Materials"

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A special issue of Materials (ISSN 1996-1944).

Deadline for manuscript submissions: closed (15 June 2014)

Special Issue Editors

Guest Editor
Prof. Dr. Guillaume Habert

ETH Zurich Institute for construction and Infrastructure management Chair of Sustainable Construction Wolfgang-Pauli-Strasse, 15 IBI/HIL F 27.3 CH-8093 Zürich Switzerland
Website | E-Mail
Guest Editor
Dr. Viola John

ETH Zurich Institute for construction and Infrastructure management Wolfgang-Pauli-Strasse, 15 IBI/HIL F 28.3 CH-8093 Zürich Switzerland
Website | E-Mail

Special Issue Information

Dear Colleagues,

In the context of sustainable development and sustainable utilization of materials, the issue of recycling is of particular interest. There are huge amounts of material resources and embodied energy stored in existing building stocks and landfill worldwide. In order to reduce the exploitation of further primary resources and energy in the future, such resources from the human technosphere must be effectively made available for future use. Unfortunately, current concepts of material recycling often do not allow for a true cradle-to-cradle perspective during a material’s lifecycle. Instead, in many cases downcycling of high quality to low-quality material is the only available option. The main focus of the forthcoming special issue is therefore to present inspiring cutting edge concepts and innovative applications of sustainable material recycling and upcycling. We want to show our readers that, by thinking outside the box, it is possible to make a change for a better and more sustainable future development. For this purpose, we intend to collect state-of-the-art research articles and reviews on recycling in engineering, material science and Life Cycle Assessment (LCA) as well as original strategies for reuse, recycling and upcycling which help to “close the loop”.

Dr. Viola John
Prof. Dr. Guillaume Habert
Guest Editors

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed Open Access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1400 CHF (Swiss Francs).

Keywords

  • material recycling
  • material upcycling
  • cradle-to-cradle
  • life cycle assessment (LCA)
  • sustainable development

Published Papers (24 papers)

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Research

Open AccessArticle The Fire Resistance Performance of Recycled Aggregate Concrete Columns with Different Concrete Compressive Strengths
Materials 2014, 7(12), 7843-7860; doi:10.3390/ma7127843
Received: 10 July 2014 / Revised: 22 November 2014 / Accepted: 27 November 2014 / Published: 8 December 2014
Cited by 2 | PDF Full-text (2082 KB) | HTML Full-text | XML Full-text
Abstract
In order to ascertain the fire resistance performance of recycled aggregate concrete (RAC) components with different concrete compressive strengths, four full-scaled concrete columns were designed and tested under high temperature. Two of the four specimens were constructed by normal concrete with compressive strength
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In order to ascertain the fire resistance performance of recycled aggregate concrete (RAC) components with different concrete compressive strengths, four full-scaled concrete columns were designed and tested under high temperature. Two of the four specimens were constructed by normal concrete with compressive strength ratings of C20 and C30, respectively, while the others were made from recycled coarse aggregate (RCA) concrete of C30 and C40, respectively. Identical constant axial forces were applied to specimens while being subjected to simulated building fire conditions in a laboratory furnace. Several parameters from the experimental results were comparatively analyzed, including the temperature change, vertical displacement, lateral deflection, fire endurance, and failure characteristics of specimens. The temperature field of specimens was simulated with ABAQUS Software (ABAQUS Inc., Provindence, RI, USA) and the results agreed quite well with those from the experiments. Results show that the rate of heat transfer from the surface to the interior of the column increases with the increase of the concrete’s compressive strength for both RAC columns and normal concrete columns. Under the same initial axial force ratio, for columns with the same cross section, those with lower concrete compressive strengths demonstrate better fire resistance performance. The fire resistance performance of RAC columns is better than that of normal concrete columns, with the same concrete compressive strength. Full article
(This article belongs to the Special Issue Recycled Materials)
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Open AccessArticle Characteristics of Indium Tin Oxide (ITO) Nanoparticles Recovered by Lift-off Method from TFT-LCD Panel Scraps
Materials 2014, 7(12), 7662-7669; doi:10.3390/ma7127662
Received: 13 June 2014 / Revised: 27 October 2014 / Accepted: 17 November 2014 / Published: 27 November 2014
Cited by 8 | PDF Full-text (527 KB) | HTML Full-text | XML Full-text
Abstract
In this study, indium-tin-oxide (ITO) nanoparticles were simply recovered from the thin film transistor-liquid crystal display (TFT-LCD) panel scraps by means of lift-off method. This can be done by dissolving color filter (CF) layer which is located between ITO layer and glass substrate.
[...] Read more.
In this study, indium-tin-oxide (ITO) nanoparticles were simply recovered from the thin film transistor-liquid crystal display (TFT-LCD) panel scraps by means of lift-off method. This can be done by dissolving color filter (CF) layer which is located between ITO layer and glass substrate. In this way the ITO layer was easily lifted off the glass substrate of the panel scrap without panel crushing. Over 90% of the ITO on the TFT-LCD panel was recovered by using this method. After separating, the ITO was obtained as particle form and their characteristics were investigated. The recovered product appeared as aggregates of particles less than 100 nm in size. The weight ratio of In/Sn is very close to 91/9. XRD analysis showed that the ITO nanoparticles have well crystallized structures with (222) preferred orientation even after recovery. The method described in this paper could be applied to the industrial recovery business for large size LCD scraps from TV easily without crushing the glass substrate. Full article
(This article belongs to the Special Issue Recycled Materials)
Open AccessArticle Potential Soil Contamination in Areas Where Ferronickel Slag Is Used for Reclamation Work
Materials 2014, 7(10), 7157-7172; doi:10.3390/ma7107157
Received: 5 June 2014 / Revised: 4 October 2014 / Accepted: 7 October 2014 / Published: 23 October 2014
PDF Full-text (1386 KB) | HTML Full-text | XML Full-text
Abstract
This study aims to analyze contamination with the use of soil reclaimed with ferronickel slag (FNS). In order to investigate any contamination due to FNS disposal, soils were collected from three sites. The contamination analysis was done on these samples through a series
[...] Read more.
This study aims to analyze contamination with the use of soil reclaimed with ferronickel slag (FNS). In order to investigate any contamination due to FNS disposal, soils were collected from three sites. The contamination analysis was done on these samples through a series of laboratory tests. Furthermore, laboratory tests simulating field conditions were performed in a soil chamber. In the lab test, three leaching agents, namely fresh water, acidic water and seawater, were used. The soil samples used were sand and silt with a relative density of 40% and a compaction ratio of 90%, respectively. The pH of the effluent discharged from the experimental soil chamber was also analyzed. After leaching, soil samples were subjected to analysis. The results showed that pH was higher in the silt than in the sand. The results of the laboratory tests exhibited that leaching of hazardous elements from FNS is limited, so that it can be used as a substitute for natural aggregate in the cement industry or construction applications. Full article
(This article belongs to the Special Issue Recycled Materials)
Open AccessArticle Application of Various NDT Methods for the Evaluation of Building Steel Structures for Reuse
Materials 2014, 7(10), 7130-7144; doi:10.3390/ma7107130
Received: 11 June 2014 / Revised: 8 August 2014 / Accepted: 11 October 2014 / Published: 22 October 2014
Cited by 1 | PDF Full-text (990 KB) | HTML Full-text | XML Full-text
Abstract
The reuse system proposed by the authors is an overall business system for realizing a cyclic reuse flow through the processes of design, fabrication, construction, maintenance, demolition and storage. The reuse system is one of the methods to reduce the environmental burden in
[...] Read more.
The reuse system proposed by the authors is an overall business system for realizing a cyclic reuse flow through the processes of design, fabrication, construction, maintenance, demolition and storage. The reuse system is one of the methods to reduce the environmental burden in the field of building steel structures. These buildings are assumed to be demolished within approximately 30 years or more for physical, architectural, economic and social reasons in Japan. In this paper, focusing on building steel structures used for plants, warehouses and offices without fire protection, the performance of steel structural members for reuse is evaluated by a non-destructive test. First, performance evaluation procedures for a non-destructive test, such as mechanical properties, chemical compositions, dimension and degradation, are shown. Tensile strengths are estimated using Vickers hardness measured by a portable ultrasonic hardness tester, and chemical compositions are measured by a portable optical emission spectrometer. The weldability of steel structural members is estimated by carbon equivalent and weld crack sensitivity composition using chemical compositions. Finally, the material grade of structural members of the building steel structure for reuse is estimated based on the proposed procedures. Full article
(This article belongs to the Special Issue Recycled Materials)
Open AccessArticle Valorization of Waste Obtained from Oil Extraction in Moringa Oleifera Seeds: Coagulation of Reactive Dyes in Textile Effluents
Materials 2014, 7(9), 6569-6584; doi:10.3390/ma7096569
Received: 12 June 2014 / Revised: 2 September 2014 / Accepted: 4 September 2014 / Published: 12 September 2014
Cited by 4 | PDF Full-text (513 KB) | HTML Full-text | XML Full-text
Abstract
Moringa oleifera seeds contain about 40% of highly valued oil due to its wide range of applications, from nutritional issues to cosmetics or biodiesel production. The extraction of Moringa oil generates a waste (65%–75% of seeds weight) which contains a water soluble protein
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Moringa oleifera seeds contain about 40% of highly valued oil due to its wide range of applications, from nutritional issues to cosmetics or biodiesel production. The extraction of Moringa oil generates a waste (65%–75% of seeds weight) which contains a water soluble protein able to be used either in drinking water clarification or wastewater treatment. In this paper, the waste of Moringa oleifera extraction was used as coagulant to remove five reactive dyes from synthetic textile effluents. This waste constitutes a natural coagulant which was demonstrated to be effective for the treatment of industrial reactive dyestuff effluents, characterized by alkaline pH, high NaCl content and hydrolyzed dyes. The coagulation yield increased at high NaCl concentration, whereas the pH did not show any significant effect on dye removal. Moringa oleifera showed better results for dye removal than the conventional treatment of coagulation-flocculation with FeCl3 and polyelectrolyte. Treated water can be reused in new dyeing processes of cotton fabrics with high quality results. Full article
(This article belongs to the Special Issue Recycled Materials)
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Open AccessArticle Upgrade Recycling of Cast Iron Scrap Chips towards β-FeSi2 Thermoelectric Materials
Materials 2014, 7(9), 6304-6316; doi:10.3390/ma7096304
Received: 13 June 2014 / Revised: 26 August 2014 / Accepted: 1 September 2014 / Published: 4 September 2014
PDF Full-text (1647 KB) | HTML Full-text | XML Full-text
Abstract
The upgrade recycling of cast-iron scrap chips towards β-FeSi2 thermoelectric materials is proposed as an eco-friendly and cost-effective production process. By using scrap waste from the machining process of cast-iron components, the material cost to fabricate β-FeSi2 is reduced and the
[...] Read more.
The upgrade recycling of cast-iron scrap chips towards β-FeSi2 thermoelectric materials is proposed as an eco-friendly and cost-effective production process. By using scrap waste from the machining process of cast-iron components, the material cost to fabricate β-FeSi2 is reduced and the industrial waste is recycled. In this study, β-FeSi2 specimens obtained from cast iron scrap chips were prepared both in the undoped form and doped with Al and Co elements. The maximum figure of merit (ZT) indicated a thermoelectric performance of approximately 70% in p-type samples and nearly 90% in n-type samples compared to β-FeSi2 prepared from pure Fe and other published studies. The use of cast iron scrap chips to produce β-FeSi2 shows promise as an eco-friendly and cost-effective production process for thermoelectric materials. Full article
(This article belongs to the Special Issue Recycled Materials)
Open AccessArticle Microstructural Analysis and Rheological Modeling of Asphalt Mixtures Containing Recycled Asphalt Materials
Materials 2014, 7(9), 6254-6280; doi:10.3390/ma7096254
Received: 12 June 2014 / Revised: 17 August 2014 / Accepted: 27 August 2014 / Published: 2 September 2014
Cited by 4 | PDF Full-text (2655 KB) | HTML Full-text | XML Full-text
Abstract
The use of recycled materials in pavement construction has seen, over the years, a significant increase closely associated with substantial economic and environmental benefits. During the past decades, many transportation agencies have evaluated the effect of adding Reclaimed Asphalt Pavement (RAP), and, more
[...] Read more.
The use of recycled materials in pavement construction has seen, over the years, a significant increase closely associated with substantial economic and environmental benefits. During the past decades, many transportation agencies have evaluated the effect of adding Reclaimed Asphalt Pavement (RAP), and, more recently, Recycled Asphalt Shingles (RAS) on the performance of asphalt pavement, while limits were proposed on the amount of recycled materials which can be used. In this paper, the effect of adding RAP and RAS on the microstructural and low temperature properties of asphalt mixtures is investigated using digital image processing (DIP) and modeling of rheological data obtained with the Bending Beam Rheometer (BBR). Detailed information on the internal microstructure of asphalt mixtures is acquired based on digital images of small beam specimens and numerical estimations of spatial correlation functions. It is found that RAP increases the autocorrelation length (ACL) of the spatial distribution of aggregates, asphalt mastic and air voids phases, while an opposite trend is observed when RAS is included. Analogical and semi empirical models are used to back-calculate binder creep stiffness from mixture experimental data. Differences between back-calculated results and experimental data suggest limited or partial blending between new and aged binder. Full article
(This article belongs to the Special Issue Recycled Materials)
Open AccessArticle Pre-Saturation Technique of the Recycled Aggregates: Solution to the Water Absorption Drawback in the Recycled Concrete Manufacture
Materials 2014, 7(9), 6224-6236; doi:10.3390/ma7096224
Received: 18 June 2014 / Revised: 20 August 2014 / Accepted: 27 August 2014 / Published: 1 September 2014
Cited by 5 | PDF Full-text (866 KB) | HTML Full-text | XML Full-text
Abstract
The replacement of natural aggregates by recycled aggregates in the concrete manufacturing has been spreading worldwide as a recycling method to counteract the large amount of construction and demolition waste. Although legislation in this field is still not well developed, many investigations demonstrate
[...] Read more.
The replacement of natural aggregates by recycled aggregates in the concrete manufacturing has been spreading worldwide as a recycling method to counteract the large amount of construction and demolition waste. Although legislation in this field is still not well developed, many investigations demonstrate the possibilities of success of this trend given that concrete with satisfactory mechanical and durability properties could be achieved. However, recycled aggregates present a low quality compared to natural aggregates, the water absorption being their main drawback. When used untreated in concrete mix, the recycled aggregate absorb part of the water initially calculated for the cement hydration, which will adversely affect some characteristics of the recycled concrete. This article seeks to demonstrate that the technique of pre-saturation is able to solve the aforementioned problem. In order to do so, the water absorption of the aggregates was tested to determine the necessary period of soaking to bring the recycled aggregates into a state of suitable humidity for their incorporation into the mixture. Moreover, several concrete mixes were made with different replacement percentages of natural aggregate and various periods of pre-saturation. The consistency and compressive strength of the concrete mixes were tested to verify the feasibility of the proposed technique. Full article
(This article belongs to the Special Issue Recycled Materials)
Open AccessArticle Life Cycle Assessment of Completely Recyclable Concrete
Materials 2014, 7(8), 6010-6027; doi:10.3390/ma7086010
Received: 15 June 2014 / Revised: 13 August 2014 / Accepted: 15 August 2014 / Published: 21 August 2014
Cited by 8 | PDF Full-text (2203 KB) | HTML Full-text | XML Full-text
Abstract
Since the construction sector uses 50% of the Earth’s raw materials and produces 50% of its waste, the development of more durable and sustainable building materials is crucial. Today, Construction and Demolition Waste (CDW) is mainly used in low level applications, namely as
[...] Read more.
Since the construction sector uses 50% of the Earth’s raw materials and produces 50% of its waste, the development of more durable and sustainable building materials is crucial. Today, Construction and Demolition Waste (CDW) is mainly used in low level applications, namely as unbound material for foundations, e.g., in road construction. Mineral demolition waste can be recycled as crushed aggregates for concrete, but these reduce the compressive strength and affect the workability due to higher values of water absorption. To advance the use of concrete rubble, Completely Recyclable Concrete (CRC) is designed for reincarnation within the cement production, following the Cradle-to-Cradle (C2C) principle. By the design, CRC becomes a resource for cement production because the chemical composition of CRC will be similar to that of cement raw materials. If CRC is used on a regular basis, a closed concrete-cement-concrete material cycle will arise, which is completely different from the current life cycle of traditional concrete. Within the research towards this CRC it is important to quantify the benefit for the environment and Life Cycle Assessment (LCA) needs to be performed, of which the results are presented in a this paper. It was observed that CRC could significantly reduce the global warming potential of concrete. Full article
(This article belongs to the Special Issue Recycled Materials)
Open AccessArticle Experimental Study on the Seismic Performance of Recycled Concrete Brick Walls Embedded with Vertical Reinforcement
Materials 2014, 7(8), 5934-5958; doi:10.3390/ma7085934
Received: 11 June 2014 / Revised: 6 August 2014 / Accepted: 6 August 2014 / Published: 19 August 2014
Cited by 3 | PDF Full-text (2958 KB) | HTML Full-text | XML Full-text
Abstract
Recycled concrete brick (RCB) is manufactured by recycled aggregate processed from discarded concrete blocks arising from the demolishing of existing buildings. This paper presents research on the seismic performance of RCB masonry walls to assess the applicability of RCB for use in rural
[...] Read more.
Recycled concrete brick (RCB) is manufactured by recycled aggregate processed from discarded concrete blocks arising from the demolishing of existing buildings. This paper presents research on the seismic performance of RCB masonry walls to assess the applicability of RCB for use in rural low-rise constructions. The seismic performance of a masonry wall is closely related to the vertical load applied to the wall. Thus, the compressive performance of RCB masonry was investigated firstly by constructing and testing eighteen RCB masonry compressive specimens with different mortar strengths. The load-bearing capacity, deformation and failure characteristic were analyzed, as well. Then, a quasi-static test was carried out to study the seismic behavior of RCB walls by eight RCB masonry walls subjected to an axial compressive load and a reversed cyclic lateral load. Based on the test results, equations for predicting the compressive strength of RCB masonry and the lateral ultimate strength of an RCB masonry wall were proposed. Experimental values were found to be in good agreement with the predicted values. Meanwhile, finite element analysis (FEA) and parametric analysis of the RCB walls were carried out using ABAQUS software. The elastic-plastic deformation characteristics and the lateral load-displacement relations were studied. Full article
(This article belongs to the Special Issue Recycled Materials)
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Open AccessArticle Material and Structural Performance Evaluations of Hwangtoh Admixtures and Recycled PET Fiber-Added Eco-Friendly Concrete for CO2 Emission Reduction
Materials 2014, 7(8), 5959-5981; doi:10.3390/ma7085959
Received: 22 April 2014 / Revised: 13 August 2014 / Accepted: 14 August 2014 / Published: 19 August 2014
Cited by 3 | PDF Full-text (2234 KB) | HTML Full-text | XML Full-text
Abstract
In order to reduce carbon dioxide (CO2) emissions and produce an eco-friendly construction material, a type of concrete that uses a minimal amount of cement, yet still retains equivalent properties to ordinary cement concrete, has been developed and studied all over
[...] Read more.
In order to reduce carbon dioxide (CO2) emissions and produce an eco-friendly construction material, a type of concrete that uses a minimal amount of cement, yet still retains equivalent properties to ordinary cement concrete, has been developed and studied all over the world. Hwangtoh, a type of red clay broadly deposited around the world, has traditionally been considered an eco-friendly construction material, with bonus advantages of having health and cost benefits. Presently, Hwangtoh is not commonly used as a modern construction material due to properties such as low strength and high rates of shrinkage cracking. Recent studies, however, have shown that Hwangtoh can be used as a mineral admixture to improve the strength of concrete. In addition, polyethylene terephthalate (PET) fibers recycled from PET bottle waste can be used to control shrinkage cracks in Hwangtoh concrete. Therefore, in this study, performance verification is conducted on newly developed Hwangtoh concrete mixed with short recycled PET fibers. The results show that Hwangtoh concrete has compressive strength, elastic modulus, and pH properties that are similar to these features in ordinary cement concrete. The properties of carbonation depth and creep strain of Hwangtoh concrete, however, are larger and smaller, respectively, than in ordinary cement concrete. According to flexural tests, reinforced concrete (RC) specimens cast with Hwangtoh admixtures (with and without PET fibers) possess similar or better capacities than ordinary RC specimens. The addition of PET fibers significantly improves the structural ductility of RC specimens under normal environmental conditions. However, the implementations of the concrete in aggressive environment must be carefully considered, since a previous study result indicates degradation of its durability performance in aggressive environments, such as seawater [1]. The results of this study validate the possibility of using eco-friendly Hwangtoh concrete reinforced with recycled PET fibers as a structural material for modern construction. Full article
(This article belongs to the Special Issue Recycled Materials)
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Open AccessArticle Recycling of Coal Fly Ash for the Fabrication of Porous Mullite/Alumina Composites
Materials 2014, 7(8), 5982-5991; doi:10.3390/ma7085982
Received: 13 June 2014 / Revised: 11 August 2014 / Accepted: 12 August 2014 / Published: 19 August 2014
Cited by 3 | PDF Full-text (4214 KB) | HTML Full-text | XML Full-text
Abstract
Coal fly ash with the addition of Al2O3 was recycled to produce mullite/alumina composites and the camphene-based freeze casting technique was processed to develop a controlled porous structure with improved mechanical strength. Many rod-shaped mullite crystals, formed by the mullitization
[...] Read more.
Coal fly ash with the addition of Al2O3 was recycled to produce mullite/alumina composites and the camphene-based freeze casting technique was processed to develop a controlled porous structure with improved mechanical strength. Many rod-shaped mullite crystals, formed by the mullitization of coal fly ash in the presence of enough silicate, melt. After sintering at 1300–1500 °C with the initial solid loadings of 30–50 wt.%, interconnected macro-sized pore channels with nearly circular-shaped cross-sections developed along the macroscopic solidification direction of camphene solvent used in freeze casting and a few micron-sized pores formed in the walls of the pore channels. The macro-pore size of the mullite/alumina composites was in the range 20–25 μm, 18–20 μm and 15–17 μm with reverse dependence on the sintering temperature at 30, 40 and 50 wt.% solid loading, respectively. By increasing initial solid loading and the sintering temperature, the sintered porosity was reduced from 79.8% to 31.2%, resulting in an increase in the compressive strength from 8.2 to 80.4 MPa. Full article
(This article belongs to the Special Issue Recycled Materials)
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Open AccessArticle The Use of Deconstructed Tires as Elastic Elements in Railway Tracks
Materials 2014, 7(8), 5903-5919; doi:10.3390/ma7085903
Received: 13 June 2014 / Revised: 29 July 2014 / Accepted: 31 July 2014 / Published: 18 August 2014
Cited by 2 | PDF Full-text (1152 KB) | HTML Full-text | XML Full-text
Abstract
Elastic elements such as rail pads, under sleeper pads and under ballast mats are railway components that allow for a reduction in track deterioration and vibrations. And they are furthermore commonly used to obtain an optimal vertical stiffness of the infrastructure. However, the
[...] Read more.
Elastic elements such as rail pads, under sleeper pads and under ballast mats are railway components that allow for a reduction in track deterioration and vibrations. And they are furthermore commonly used to obtain an optimal vertical stiffness of the infrastructure. However, the use of elastomeric materials can increase construction costs and the consumption of raw materials. Thus, the utilization of used tire layers offers an alternative to reuse an abundant waste reducing the cost of elastic elements. In addition, an innovator technique allows deconstructing tire layers without grinding up the material, reducing production costs at the same time that tire properties are remained. This research is focused on the study of the viability of developing elastic components from used tire layers by evaluating the influence of thickness, the resistance capacity of the elements and their behavior in a ballast box. Results indicate the ability of tire pads to manufacture elastic elements (rail pads, under sleeper pads and under ballast mats) to be used in railway tracks. Full article
(This article belongs to the Special Issue Recycled Materials)
Open AccessArticle Structural and Mechanical Characterization of Sustainable Composites Based on Recycled and Stabilized Fly Ash
Materials 2014, 7(8), 5920-5933; doi:10.3390/ma7085920
Received: 13 June 2014 / Revised: 3 August 2014 / Accepted: 5 August 2014 / Published: 18 August 2014
Cited by 5 | PDF Full-text (746 KB) | HTML Full-text | XML Full-text
Abstract
This paper reports the results on the use of an innovative inert, based on stabilized fly ash from municipal solid waste incineration as a filler for polypropylene. The starting material, which contains large quantities of leachable Pb and Zn, was stabilized by means
[...] Read more.
This paper reports the results on the use of an innovative inert, based on stabilized fly ash from municipal solid waste incineration as a filler for polypropylene. The starting material, which contains large quantities of leachable Pb and Zn, was stabilized by means of an innovative process using rice husk ash as a waste silica source, together with other fly ashes, such as coal fly ash and flue gas desulfurization residues. The use of all waste materials to obtain a new filler makes the proposed technology extremely sustainable and competitive. The new composites, obtained by using the stabilized material as a filler for polypropylene, were characterized and their mechanical properties were also investigated. A comparison with a traditional polypropylene and calcium carbonate based compound was also done. This research activity was realized in the frame of the COSMOS-RICE project, financed by the EU Commission. Full article
(This article belongs to the Special Issue Recycled Materials)
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Open AccessArticle Quality Assessment of Mixed and Ceramic Recycled Aggregates from Construction and Demolition Wastes in the Concrete Manufacture According to the Spanish Standard
Materials 2014, 7(8), 5843-5857; doi:10.3390/ma7085843
Received: 18 June 2014 / Revised: 19 July 2014 / Accepted: 7 August 2014 / Published: 13 August 2014
Cited by 4 | PDF Full-text (786 KB) | HTML Full-text | XML Full-text
Abstract
Construction and demolition waste (CDW) constitutes an increasingly significant problem in society due to the volume generated, rendering sustainable management and disposal problematic. The aim of this study is to identify a possible reuse option in the concrete manufacturing for recycled aggregates with
[...] Read more.
Construction and demolition waste (CDW) constitutes an increasingly significant problem in society due to the volume generated, rendering sustainable management and disposal problematic. The aim of this study is to identify a possible reuse option in the concrete manufacturing for recycled aggregates with a significant ceramic content: mixed recycled aggregates (MixRA) and ceramic recycled aggregates (CerRA). In order to do so, several tests are conducted in accordance with the Spanish Code on Structural Concrete (EHE-08) to determine the composition in weight and physic-mechanical characteristics (particle size distributions, fine content, sand equivalent, density, water absorption, flakiness index, and resistance to fragmentation) of the samples for the partial inclusion of the recycled aggregates in concrete mixes. The results of these tests clearly support the hypothesis that this type of material may be suitable for such partial replacements if simple pretreatment is carried out. Furthermore, this measure of reuse is in line with European, national, and regional policies on sustainable development, and presents a solution to the environmental problem caused by the generation of CDW. Full article
(This article belongs to the Special Issue Recycled Materials)
Open AccessArticle The Influence of Different Recycling Scenarios on the Mechanical Design of an LED Weatherproof Light Fitting
Materials 2014, 7(8), 5769-5788; doi:10.3390/ma7085769
Received: 13 June 2014 / Revised: 4 August 2014 / Accepted: 5 August 2014 / Published: 11 August 2014
Cited by 4 | PDF Full-text (1047 KB) | HTML Full-text | XML Full-text
Abstract
This paper analyzes the high relevance of material selection for the sustainable development of an LED weatherproof light fitting. The research reveals how this choice modifies current and future end of life scenarios and can reduce the overall environmental impact. This life cycle
[...] Read more.
This paper analyzes the high relevance of material selection for the sustainable development of an LED weatherproof light fitting. The research reveals how this choice modifies current and future end of life scenarios and can reduce the overall environmental impact. This life cycle assessment has been carried out with Ecotool, a software program especially developed for designers to assess the environmental performance of their designs at the same time that they are working on them. Results show that special attention can be put on the recycling and reusing of the product from the initial stages of development. Full article
(This article belongs to the Special Issue Recycled Materials)
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Open AccessArticle Spark Plasma Sintering As a Solid-State Recycling Technique: The Case of Aluminum Alloy Scrap Consolidation
Materials 2014, 7(8), 5664-5687; doi:10.3390/ma7085664
Received: 26 June 2014 / Revised: 26 July 2014 / Accepted: 29 July 2014 / Published: 6 August 2014
Cited by 7 | PDF Full-text (1996 KB) | HTML Full-text | XML Full-text
Abstract
Recently, “meltless” recycling techniques have been presented for the light metals category, targeting both energy and material savings by bypassing the final recycling step of remelting. In this context, the use of spark plasma sintering (SPS) is proposed in this paper as a
[...] Read more.
Recently, “meltless” recycling techniques have been presented for the light metals category, targeting both energy and material savings by bypassing the final recycling step of remelting. In this context, the use of spark plasma sintering (SPS) is proposed in this paper as a novel solid-state recycling technique. The objective is two-fold: (I) to prove the technical feasibility of this approach; and (II) to characterize the recycled samples. Aluminum (Al) alloy scrap was selected to demonstrate the SPS effectiveness in producing fully-dense samples. For this purpose, Al alloy scrap in the form of machining chips was cold pre-compacted and sintered bellow the solidus temperature at 490 °C, under elevated pressure of 200 MPa. The dynamic scrap compaction, combined with electric current-based joule heating, achieved partial fracture of the stable surface oxides, desorption of the entrapped gases and activated the metallic surfaces, resulting in efficient solid-state chip welding eliminating residual porosity. The microhardness, the texture, the mechanical properties, the microstructure and the density of the recycled specimens have been investigated. An X-ray computed tomography (CT) analysis confirmed the density measurements, revealing a void-less bulk material with homogeneously distributed intermetallic compounds and oxides. The oxide content of the chips incorporated within the recycled material slightly increases its elastic properties. Finally, a thermal distribution simulation of the process in different segments illustrates the improved energy efficiency of this approach. Full article
(This article belongs to the Special Issue Recycled Materials)
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Open AccessArticle Preparation and Characterization of Bioplastic-Based Green Renewable Composites from Tapioca with Acetyl Tributyl Citrate as a Plasticizer
Materials 2014, 7(8), 5617-5632; doi:10.3390/ma7085617
Received: 9 June 2014 / Revised: 25 July 2014 / Accepted: 29 July 2014 / Published: 4 August 2014
Cited by 10 | PDF Full-text (1227 KB) | HTML Full-text | XML Full-text
Abstract
Granular tapioca was thermally blended with poly(lactic acid) (PLA). All blends were prepared using a plasti-corder and characterized for tensile properties, thermal properties and morphology. Scanning electron micrographs showed that phase separation occurred, leading to poor tensile properties. Therefore, methylenediphenyl diisocyanate (MDI) was
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Granular tapioca was thermally blended with poly(lactic acid) (PLA). All blends were prepared using a plasti-corder and characterized for tensile properties, thermal properties and morphology. Scanning electron micrographs showed that phase separation occurred, leading to poor tensile properties. Therefore, methylenediphenyl diisocyanate (MDI) was used as an interfacial compatibilizer to improve the mechanical properties of PLA/tapioca blends. The addition of MDI could improve the tensile strength of the blend with 60 wt% tapioca, from 19.8 to 42.6 MPa. In addition, because PLA lacked toughness, acetyl tributyl citrate (ATBC) was added as a plasticizer to improve the ductility of PLA. A significant decrease in the melting point and glass-transition temperature was observed on the basis of differential scanning calorimetry, which indicated that the PLA structure was not dense after ATBC was added. As such, the brittleness was improved, and the elongation at break was extended to several hundred percent. Therefore, mixing ATBC with PLA/tapioca/MDI blends did exhibit the effect of plasticization and biodegradation. The results also revealed that excessive plasticizer would cause the migration of ATBC and decrease the tensile properties. Full article
(This article belongs to the Special Issue Recycled Materials)
Open AccessArticle Magnetic Glass Ceramics by Sintering of Borosilicate Glass and Inorganic Waste
Materials 2014, 7(8), 5565-5580; doi:10.3390/ma7085565
Received: 23 May 2014 / Revised: 16 July 2014 / Accepted: 21 July 2014 / Published: 31 July 2014
Cited by 6 | PDF Full-text (1606 KB) | HTML Full-text | XML Full-text
Abstract
Ceramics and glass ceramics based on industrial waste have been widely recognized as competitive products for building applications; however, there is a great potential for such materials with novel functionalities. In this paper, we discuss the development of magnetic sintered glass ceramics based
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Ceramics and glass ceramics based on industrial waste have been widely recognized as competitive products for building applications; however, there is a great potential for such materials with novel functionalities. In this paper, we discuss the development of magnetic sintered glass ceramics based on two iron-rich slags, coming from non-ferrous metallurgy and recycled borosilicate glass. The substantial viscous flow of the glass led to dense products for rapid treatments at relatively low temperatures (900–1000 °C), whereas glass/slag interactions resulted in the formation of magnetite crystals, providing ferrimagnetism. Such behavior could be exploited for applying the obtained glass ceramics as induction heating plates, according to preliminary tests (showing the rapid heating of selected samples, even above 200 °C). The chemical durability and safety of the obtained glass ceramics were assessed by both leaching tests and cytotoxicity tests. Full article
(This article belongs to the Special Issue Recycled Materials)
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Open AccessArticle Recycling of Clay Sediments for Geopolymer Binder Production. A New Perspective for Reservoir Management in the Framework of Italian Legislation: The Occhito Reservoir Case Study
Materials 2014, 7(8), 5603-5616; doi:10.3390/ma7085603
Received: 14 June 2014 / Revised: 9 July 2014 / Accepted: 21 July 2014 / Published: 31 July 2014
Cited by 12 | PDF Full-text (1094 KB) | HTML Full-text | XML Full-text
Abstract
Reservoir silting is an unavoidable issue. It is estimated that in Italy, the potential rate of silting-up in large reservoirs ranges from 0.1% to 1% in the presence of wooded river basins and intensive agricultural land use, respectively. In medium and small-sized reservoirs,
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Reservoir silting is an unavoidable issue. It is estimated that in Italy, the potential rate of silting-up in large reservoirs ranges from 0.1% to 1% in the presence of wooded river basins and intensive agricultural land use, respectively. In medium and small-sized reservoirs, these values vary between 0.3% and 2%. Considering both the types of reservoirs, the annual average loss of storage capacity would be of about 1.59%. In this paper, a management strategy aimed at sediment productive reuse is presented. Particularly, the main engineering outcomes of an extensive experimental program on geopolymer binder synthesis is reported. The case study deals with Occhito reservoir, located in Southern Italy. Clay sediments coming from this silted-up artificial lake were characterized, calcined and activated, by means of a wide set of alkaline activating solutions. The results showed the feasibility of this recovery process, optimizing a few chemical parameters. The possible reuse in building material production (binders, precast concrete, bricks, etc.) represents a relevant sustainable alternative to landfill and other more consolidated practices. Full article
(This article belongs to the Special Issue Recycled Materials)
Open AccessArticle Thermodynamic Analysis for the Refining Ability of Salt Flux for Aluminum Recycling
Materials 2014, 7(8), 5543-5553; doi:10.3390/ma7085543
Received: 15 June 2014 / Revised: 20 July 2014 / Accepted: 21 July 2014 / Published: 30 July 2014
Cited by 2 | PDF Full-text (2740 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The removability of impurities during the aluminum remelting process by oxidation was previously investigated by our research group. In the present work, alternative impurity removal with chlorination has been evaluated by thermodynamic analysis. For 43 different elements, equilibrium distribution ratios among metal, chloride
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The removability of impurities during the aluminum remelting process by oxidation was previously investigated by our research group. In the present work, alternative impurity removal with chlorination has been evaluated by thermodynamic analysis. For 43 different elements, equilibrium distribution ratios among metal, chloride flux and oxide slag phases in the aluminum remelting process were calculated by assuming the binary systems of aluminum and an impurity element. It was found that the removability of impurities isn’t significantly affected by process parameters such as chloride partial pressure, temperature and flux composition. It was shown that Ho, Dy, Li, La, Mg, Gd, Ce, Yb, Ca and Sr can be potentially eliminated into flux by chlorination from the remelted aluminum. Chlorination and oxidation are not effective to remove other impurities from the melting aluminum, due to the limited parameters which can be controlled during the remelting process. It follows that a proper management of aluminum scrap such as sorting based on the composition of the products is important for sustainable aluminum recycling. Full article
(This article belongs to the Special Issue Recycled Materials)
Open AccessArticle A Perspective on the Prowaste Concept: Efficient Utilization of Plastic Waste through Product Design and Process Innovation
Materials 2014, 7(7), 5385-5402; doi:10.3390/ma7075385
Received: 12 May 2014 / Revised: 16 July 2014 / Accepted: 21 July 2014 / Published: 23 July 2014
PDF Full-text (1427 KB) | HTML Full-text | XML Full-text
Abstract
This work is aimed to present an innovative technology for the reinforcement of beams for urban furniture, produced by in-mold extrusion of plastics from solid urban waste. This material, which is usually referred to as “recycled plastic lumber”, is characterized by very poor
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This work is aimed to present an innovative technology for the reinforcement of beams for urban furniture, produced by in-mold extrusion of plastics from solid urban waste. This material, which is usually referred to as “recycled plastic lumber”, is characterized by very poor mechanical properties, which results in high deflections under flexural loads, particularly under creep conditions. The Prowaste project, founded by the EACI (European Agency for Competitiveness and Innovation) in the framework of the Eco-Innovation measure, was finalized to develop an innovative technology for selective reinforcement of recycled plastic lumber. Selective reinforcement was carried out by the addition of pultruded glass rods in specific positions with respect to the cross section of the beam, which allowed optimizing the reinforcing efficiency. The reinforcement of the plastic lumber beams with pultruded rods was tested at industrial scale plant, at Solteco SL (Alfaro, Spain). The beams obtained, characterized by low cost and weight, were commercialized by the Spanish company. The present paper presents the most relevant results of the Prowaste project. Initially, an evaluation of the different materials candidates for the reinforcement of recycled plastic lumber is presented. Plastic lumber beams produced in the industrial plant were characterized in terms of flexural properties. The results obtained are interpreted by means of beam theory, which allows for extrapolation of the characteristic features of beams produced by different reinforcing elements. Finally, a theoretical comparison with other approaches which can be used for the reinforcement of plastic lumber is presented, highlighting that, among others, the Prowaste concept maximizes the stiffening efficiency, allowing to significantly reduce the weight of the components. Full article
(This article belongs to the Special Issue Recycled Materials)
Open AccessArticle Influence of Aggregate Coated with Modified Sulfur on the Properties of Cement Concrete
Materials 2014, 7(6), 4739-4754; doi:10.3390/ma7064739
Received: 21 April 2014 / Revised: 10 June 2014 / Accepted: 10 June 2014 / Published: 20 June 2014
Cited by 1 | PDF Full-text (1646 KB) | HTML Full-text | XML Full-text
Abstract
This paper proposes the mixing design of concrete having modified sulfur-coated aggregate (MSCA) to enhance the durability of Portland cement concrete. The mechanical properties and durability of the proposed MSCA concrete were evaluated experimentally. Melting-modified sulfur was mixed with aggregate in order to
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This paper proposes the mixing design of concrete having modified sulfur-coated aggregate (MSCA) to enhance the durability of Portland cement concrete. The mechanical properties and durability of the proposed MSCA concrete were evaluated experimentally. Melting-modified sulfur was mixed with aggregate in order to coat the aggregate surface at a speed of 20 rpm for 120 s. The MSCA with modified sulfur corresponding to 5% of the cement weight did not significantly affect the flexural strength in a prism concrete beam specimen, regardless of the water-cement ratio (W/C). However, a dosage of more than 7.5% decreased the flexural strength. On the other hand, the MSCA considerably improved the resistance to the sulfuric acid and the freezing-thawing, regardless of the sulfur dosage in the MSCA. The coating modified sulfur of 5% dosage consequently led to good results for the mechanical properties and durability of MSCA concrete. Full article
(This article belongs to the Special Issue Recycled Materials)
Open AccessArticle Flowable Backfill Materials from Bottom Ash for Underground Pipeline
Materials 2014, 7(5), 3337-3352; doi:10.3390/ma7053337
Received: 14 February 2014 / Revised: 9 April 2014 / Accepted: 23 April 2014 / Published: 25 April 2014
Cited by 1 | PDF Full-text (1184 KB) | HTML Full-text | XML Full-text
Abstract
The purpose of this study was to investigate the relationship between strength and strain in manufacturing controlled low strength materials to recycle incineration bottom ash. Laboratory tests for controlled low strength materials with bottom ash and recycled in-situ soil have been carried out.
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The purpose of this study was to investigate the relationship between strength and strain in manufacturing controlled low strength materials to recycle incineration bottom ash. Laboratory tests for controlled low strength materials with bottom ash and recycled in-situ soil have been carried out. The optimum mixing ratios were 25%–45% of in-situ soil, 30% of bottom ash, 10%–20% of fly ash, 0%–3% of crumb rubber, 3% of cement, and 22% of water. Each mixture satisfied the standard specifications: a minimum 20 cm of flowability and 127 kPa of unconfined compressive strength. The average secant modulus (E50) was (0.07–0.08) qu. The ranges of the internal friction angle and cohesion for mixtures were 36.5°–46.6° and 49.1–180 kPa, respectively. The pH of all of the mixtures was over 12, which is strongly alkaline. Small-scale chamber tests for controlled low strength materials with bottom ash and recycled in-situ soil have been carried out. Vertical deflection of 0.88–2.41 mm and horizontal deflection of 0.83–3.72 mm were measured during backfilling. The vertical and horizontal deflections of controlled low strength materials were smaller than that of sand backfill. Full article
(This article belongs to the Special Issue Recycled Materials)

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