Papers by Keyword: Recycling

Abstract: The present research aims to simultaneously have positive contribution in two environmental issues identified on global scale, but also locally, in Romania: the waste generation due to industrial processes, on one hand, and on the other hand, the exhaustible natural resources constant increasing demand and consumption, in the construction industry as well. The use of abrasive waterjet (AWJ) sand in specific industries, for material processing purpose, represents an advantageous and efficient methodology, with increased domain of applicability and experiencing a significant development and improvement in the last years; still, besides the numerous benefits of the AWJ cutting and material processing techniques, they also generate collateral by-products, mostly converted into wastes: the abrasive materials (Garnet Sands) used during the AWJ cutting generate a sludge, generally unutilized and randomly deserted into damps (Spent Garnets, SG). In the same time, the construction industry and the corresponding mortar and concrete production segments, present accelerated growth, associated with global population fast increase (mainly in urban poles) and also with the industrial drive. The population growth and the industry expansion demand the corresponding infrastructure, civil, industrial, agrozootechnical, road and energetic, etc., leading to related request for building materials, concrete and natural resource consumption, like aggregates. This was the context which induced the idea of potentially valorizing the SG industrial by-products, generated by the local AWJ cutting industry, into construction materials, namely fine grain aggregates substitution in mortar and concrete. In order to evaluate the waste compatibility to a typical composition of cementitious material, a regular mortar was developed, considered the Reference (R) and further partial substitution of the usual sand was performed, by using the Spent Garnet wastes generated by two local companies. The substitution percentage was established in accordance to the previous studies in the topic, and ranged from 10 to 50% with respect to the sand quantity in the Reference mix. The mechanical performance of the mortars was analyzed at specific ages, in order to establish the viability of the substitution: 7day-testing, 14-day testing, 28 day-testing. The first results of the experimental study, focused on mechanical and physical characteristics of the mixes, are clearly encouraging, leading to the conclusion that SG by-products could be efficiently integrated in concrete and mortar mixes, as partial replacement of the regular sand; thus, the study opens the path to a sustainable, preventive solution for industrial waste generation and natural resources consumption as well. The potential use of SG as aggregate partial replacement in pavement eco-blocks is also considered, as future direction of research.

Abstract: A strip caster was used to cast two types of aluminium alloys: an almost eutectic Al-Si alloy (Al 10 Si) with contaminants of 0.6 Fe, 0.2 Pb, and 1.4 Sn, which exhibits a polyphase microstructure upon solidification, and recycled aluminium beverage cans made from Al 0.8 Mn alloy containing 0.4 Si, 0.5 Fe, and 0.1 Mg, which has a monophase microstructure upon solidification. The molten materials were poured at 650 oC (Al 10 Si) and 670 oC (Al 0.8 Mn, 0.4 Si, 0.5 Fe, 0.1 Mg) on a cooling slope specially designed to obtain a semisolid material. This semisolid material was then dragged between rolls at a rate of 0.2 m/s to obtain high-quality metal strips. There was less eutectic modification with larger Al-α grains in the middle region of the sheet between the fine eutectic layers, indicating a lower cooling rate. However, during the recycling of aluminium beverage cans, large grains were formed with a columnar structure at the interface of the rolls, and semisolid melts with cracks were formed between the columnar grain boundaries owing to the compression of the rolls. The middle of these grains contained smaller equiaxial grains that were subjected to dragging. The as-cast specimens were submitted to homogenisation heat treatment at 560 oC for a period of 10 h and cooled to room temperature before being cold rolled (Temper H18) and recrystallised (Temper O) to examine the effect of these treatments on the tensile mechanical properties. During cold rolling (Temper H-18), grain alignment occurred with a yield stress, maximum stress, and elongation of 209.5 MPa, 210.1 MPa, and 2.8%, respectively. The strength decreased (yield stress of 58 MPa and maximum stress of 120.2 MPa) under recrystallisation conditions (Temper O), but the ductility increased (8.9%). This is in contrast to the Al-Si (Al 10Si) strip, which exhibited a yield stress, maximum stress, and elongation of 103.3 MPa, 128.7 MPa, and 1.9%, respectively. The A1 10Si strips also fractured during cold rolling, indicating high material fragility.

Abstract: Recycling of construction material helps to conserve the limited landfill spaces and increase the gained cost. Among various types of materials timber and concrete & masonry waste were the most generated waste at construction sites. The recycling practices at construction sites reduces the generation of C&D waste and increase the gained cost. Therefore, this paper aimed to investigate the total recycled C&D waste and gained amount between two different construction sites. The data was collected over 6 months period using direct and indirect measurement. The paper revealed that the gained cost for Site I is RM 29,880.90 while for site II is RM 38,217.80. The CBA revealed that it was positive for these projects with benefits of RM 360.90 and RM 927.80 respectively. This paper provides an awareness for contractors regarding costings that can be gained if the C&D waste was adequately managed. Thus, it directly benefits the construction industry in terms of economic sustainability for a construction project

Abstract: Population growth, urbanization, industrialization, developing technology, increasing welfare level and changing consumption habits cause solid wastes to increase day by day. There are also sub-waste groups that have not yet been fully recognized among the solid waste groups in which textile wastes have a large share. One of them is pantyhose, which has been indispensable for modern life since the day it was presented to the consumer. These socks, which are made of polyamide and elastane fibers that are easily punctured, run and become unusable when worn once or several times, are generally thrown away after use. These pantyhose wastes, which are not biodegradable due to their raw materials, also pose an environmental risk. Within the scope of the study, thermal and sound insulation properties of carded and needle-punched pantyhose wastes are investigated. The results show that the thermal and acoustic properties of the developed material are at a sufficient level, and it has ensured that polyamide wastes, which have superior properties among thermoplastic polymers and have high economic value, are brought back into the economy.

Abstract: This research provides the analysis of the mill scale and plastic waste properties, as well as ways of their complex recycling. Preliminary experiments on the formation of briquettes were made. The results of preliminary experiments on mill scale grinding in a cone inertial crusher and the formation of briquettes together with plastic are presented. This research has revealed the possibility of creating a briquette charge material for further processing in steelmaking processes. The addition of a plasticizer is necessary to improve the formability of the samples during pressing.

Abstract: Recycling of aluminium (Al) from waste aluminium scraps for fabricating aluminium casts is a waste management technique suitable for reducing environmental pollution. The aluminium casts can be further processed into different materials of engineering interests such as heater-cooler (thermal) blocks. In this study, the microstructural characterization of aluminium cast fabricated from recycled aluminium waste and adapted for use via the (steady-state technique) as heater-cooler blocks required in the determination of the thermal conductivity of conducting solid composites was investigated. The characterization was investigated using the Scanning Electron Microscopy (SEM), Energy Displacer Spectroscopy (EDS), X-ray Diffractometer (XRD), and X-ray Fluorescence (XRF). The XRD result confirms the crystalline structure of aluminium on the fabricated aluminium cast. The elemental composition results confirmed that the fabricated cast contains 90% Al, with Silicon (Si) accounting for about 8% of the chemical composition while the remaining 2% was contributed by C, O, Fe, Zn, and Cu. The compositional change observed during characterization was attributed to the recycling process used in fabricating the aluminium cast.

Abstract: The world is evolving toward extending the life of commodities and decreasing waste by recycling. The purpose of this study is to improve resistance of epoxy against the corrosive conditions by reinforcing it with available chemically resistant and low cost materials. Selection of Glass wastes to reinforce epoxy with 50% by weight. Preparation of four sets of samples for this purpose, two sets of samples make and cure at room temperature, while the others cure at 50°C for two hours. Each set make up of both reinforced and unreinforced epoxy. Immersion of these samples in different environment (Water, NaOH, HCl, Benzene and Kerosene) to find out the resistance of the epoxy after reinforcing. After immersion for six months, it is found that the composite seems more resistance compared to matrix material alone. Composites reinforced by glass particles show an increase in mechanical properties when compared to elegant epoxy resin. Density, Vickers hardness and Modulus of elasticity values increased by (31%, 67% and 62%) respectively for composite at room temperature. Improvement of the resistance after the post curing of unreinforced and reinforced epoxy. The solutions that have highest effect for unreinforced samples at room temperature are (HCl and Water). This indicates that epoxy acquire resistance after reinforcing with glass waste which enables it to be utilize in different applications.

Abstract: This work presents the recyclability of waste plastics into mechanically strong water-resistant carbon foam by chemical blowing method and low-temperature carbonization. Waste polystyrene (PS) was used as a precursor. The synthetic carbon foam (CF) was characterized using scanning electron microscope (SEM), transmission electron microscope (TEM), energy dispersion X-ray spectroscopy (EDX), C-H-N-S elemental analyzer, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermal constants analyzer and universal compression tester. The synthesized carbon foam exhibits a low density (0.32 g/cm³), low thermal conductivity (0.074 W/m.K), high compressive strength (58 MPa) and high strength/density ratio (181 MPa/g/cm³). The synthesized carbon foam is a potential candidate for thermal insulation in energy-saving buildings and the technology is a simple, cheap, and sustainable approach to managing waste plastics.

Abstract: Basic oxygen furnace slag (BOF slag) contains high amount of useful oxides such as CaO, MgO, SiO₂, etc., therefore, a solution of the slag recycling would be used as a flux in pelletizing process. To understand role of slag in the pellet, this research examines the mechanical, chemical and microstructure properties of the pellets containing various amount of the slag. In the experimental process, the green pellets were made from a mixture of bentonite, iron ore and the slag. The green pellets were sintered in the resistance heating furnace maintaining temperature at 1200 °C for 120 minutes. Then the fired pellet was tested strength and observed microstructure with variation of the slag amount in the pellets. The result shown that cold compression strength of the pellets containing from 1.06 to 18.45 mass% slag was higher values than 200 kg/p, hence, the pellet was able to charge the pellets into the blast furnace. The highest strength was 342 kg/p with 5.08 mass% slag in the pellet. Besides, optical observed microstructure of the pellet indicated the phases of magnetite, hematite and silicate. In addition, the obtained results shown that there was a deterioration of porosity with increasing the slag amount. Accordingly, the porosity got a slight decrease when the slag amount increased from 1.06 to 5.08 mass% in the pellet. Once the amount of the slag was higher than 5.08 mass%, the porosity significantly reduced with increasing the slag amount; the porosity decreased from 23 to 12 %.

Abstract: Medium density fiberboard (MDF) is a wood-based engineered material, largely implemented in the manufacturing of in-house structures. Large panels are usually manufactured and shaped via machining; in this way powders are produced. Dismissed structures can also be pulverized to facilitate transportation of waste. MDF is generally dismissed through landfill or incineration. The aim of this work is to determine a recycling method for MDF powders that make it possible to obtain ready-to-use panels without using virgin or additional materials. Powders granulometry is evaluated and then grains are “direct molded” by a parallel plate hot press. Compression molding was used for this aim. Recycled panels had the size of 200x200 mm², a thickness of 5 mm, and a smooth surface without evident defects. Burrs were absent. Mechanical properties were evaluated under bending test, and a maximum strength over 8 MPa was found. Results show the feasibility of this recycling technology for MDF powders. Agglomeration occurred thanks to the powder re-activation, and possible residual reactivity.