Papers by Keyword: Recycling

Abstract: Waste from plastic materials is outstripped due to the growth of industrialization and urbanization. Plastic materials are non-biodegradable; decomposition is not possible all the time. The recycling of plastic materials by using them in concrete will be a great deal for plastic management. This research investigation aims to measure the optimum percentage of plastic in concrete without a reduction in concrete strength and shear behavior of reinforced concrete. Using the provision of Mix Design ACI 211.1-91, the M28 concrete grade was created. Plastic materials have been collected and passed through a No-4 sieve (4.76mm). The combination of fine aggregates and ground plastic materials (RPET, PP) in the weight fraction of fine aggregate mix (0%, 2%, 4%, 6%, 8%, 10%) was used in the concrete. Concrete beams (750´150´150 mm) are reinforced with two 12 mm longitudinal steel bars in the tension zone, with proper clear cover for testing the shear capacity. In order to conduct the compressive and tensile splitting test, concrete specimens with a diameter of 100 mm and a height of 200 mm were used. The experimental findings demonstrate guidelines for using plastic as a partial replacement within 2% to 4% of fine aggregate to produce the best outcomes.

Abstract: Reprocessable and recyclable self-healing rubber composites were fabricated by mixing natural rubber (NR) with carbon black (CB) filler in the presence of zinc thiolate (ZT) to form the ionic association in the rubber system. This work investigated and compared the unfilled and natural rubber filled with 5phr of carbon black. The recycling process was repeated three times, and the mechanical performance was measured each time. Tensile strength was increased by more than 430% for unfilled rubber and 520% for NR/5CB composites after the third recycling process. Tear strength was also increased with the number of the recycling process. According to a welding test ability, the developed materials showed potential for repair. Scanning electron micrographs revealed that as the recycling number increased, the white spot of ZT responsible for generating the ionic network reduced as more ZT was converted into Zn²⁺ salt bonding.

Abstract: A large amount of dust is formed as one of the primary by-products during the blast furnace ironmaking process. Iron and carbon are mainly compositions in the dust. Blast furnace dust (BFD) is cycled to protect the environment and recover valuable components. In this study, BFD is used pelletization process with iron ore concentration for raw materials charging to the iron-making furnace. The mixture of BFD and iron ore (30; 40; 50 by mass %) with 2 % bentonite as a binder was used for making pellets. The produced pellets were tested drop strength and fired at 1200 °C for 30 minutes in the atmosphere environment. Fired pellets were examined compressive strength and reduced at 900; 1000; 1100 °C in 30 minutes. Mechanical, porosity and reduction degree properties of reduced pellets were analysed. The results show that green strength and compressive strength are acceptable values. Good porosity is observed when using a high amount of BFD so that it gives a high degree of reduction. XRD, SEM were used for characterization. Iron whiskers were observed in the sample, which was reduced at 1000 °C. It is clearly shown that the pellets using BFD are appropriated for charging to blast furnace as raw materials.

Abstract: The purpose of this study is to compare binders of two different origins. The powders obtained from crushing pure C₃S and hydrated cement for 28 days with w/b=0.6 and 0.5, respectively, will be subjected to heat treatment at 800°C. This work used X-ray diffraction (XRD) as a technique to characterize. According to X-ray diffraction, heat treatment resulted in the synthesis of β-C₂S belite in the pure phase and two polymorphs α'-C₂S and β-C₂S in the cement phase. The binder regenerated from cement pastes generates C-S-H at an early stage, which can be attributed to the high reactivity of the α'-C₂S polymorph.

Abstract: Considering that velocity of diffusion in a system solute-porous material-solvent depends on several factors, (among them, the concentration differential between “solute” in the porous material and “solute” in the solvent) the diffusion process will finish only when maximum entropy is achieved. Thus, the solute concentration will be equal in the matrix and in the solvent (equilibrium concept). On the other hand, if the velocity of diffusion depends on the differential of concentration, then, the amount of materials transferred per time unit (diffusion rate) will diminish as the process goes on. Moreover, when the final concentration of solute in the porous material is desired to be lower than that of the one-stage-equilibrium, then n-more stages must be added. Thus, the decision to choose a process with one or more stages, as well as the end point in each stage (as close or as far as equilibrium) will determine processing time and the use of other resources, i.e. amount of solvent, installation size, financial investment and so on. Therefore, the objective of this study is to develop a tool that helps to optimize these decisions by using a numerical approach.

Abstract: The use of technology in Indonesia has resulted in an increasing demand for electronic and electrical goods, including printed circuit board (PCB) waste. Currently, PCB waste amounts to 20-50 million tons and continues to grow annually. Given that the composition of PCB waste consists of approximately 40% metals such as Ag, Cu, Fe, Au, Sn, and Mn, recycling PCB FR-2 waste can significantly increase its added value. One effective method is employing a concentration technique to recover these metals. This study aims to investigate the impact of particle size and centrifugal force variations on the content and recovery of Cu and Ag metals in PCB FR-2 waste using a Knelson concentrator. The concentration process involved three size variations: -63+100, -100+150, and-150#, along with three centrifugal force values: 60, 90, and 120 G Force. The results indicate that the size variation-100+150# and a centrifugal force value of 90 G Force exhibited effectiveness in recovering Cu and Ag metals, with a minimal mass loss of 3.9%. The Cu and Ag levels reached 67.49% and 0.18%, respectively, with recovery rates of 53.22% and 39.96%.

Abstract: Nowadays’ sustainability-driven systems require a product to be environmentally beneficial as well as cost-effective whilst maintaining its great performance. In these circumstances, the pavement industry has emphasized its concern over waste production, reduced materials costs and conserving resources. Henhce, the seeking for new engineering solutions to move toward more sustainable, eco-friendly, and economically beneficial management. In this context, the use of RA (Reclaimed Asphalt) in the new asphalt mixtures has generated well-defined environmental benefits especially in terms of the reduction in raw-material consumption and possibility to upcycle the waste derived from existing old pavements. This study aims to evaluate the efficiency of the addition of selected rejuvenators which help to restore some of the properties of aged bituminous binder in RA, crumb rubber and plastic (LDPE) waste on the performance of asphalt mixture designed with elevated RA content (50 %). Mechanical performance was evaluated by means of laboratory investigations for typical characteristics dedicated to durability, stiffness and cracking potential. The results showed that a proper dosage of a suitable type of rejuvenation agent as well as the crumb rubber and plastic waste can enhance the overall durability of the elevated RA content asphalt mixtures.

Abstract: The construction industry generates a significant amount of waste, posing challenges for efficient waste management and resource recovery. This paper presents a preliminary study on the use of lightweight computer vision (CV) algorithms for the automatic recognition of construction and demolition waste (CDW) materials. Utilizing image datasets acquired by drones, the study aims to develop strategies for distinguishing between individual CDW materials based on the mean intensity gradient, brightness, and relative representation of color channels. Results indicate that the proposed method can effectively recognize crucial CDW materials, paving the way for potential applications in industry and geodesy. Further research is needed to test additional materials and metrics to refine the method for practical implementation.

Abstract: Spent lithium-ion batteries (LIBs) have significantly increased due to the high consumption of LIBs for automobile applications; therefore, the recovery of valuable materials to use as the second resource can bring economic benefits and reduce an environmental impact. This study investigated the production of lithium phosphate (Li₃PO₄), which can be used as a starting material for the synthesis of LIBs, from spent LiNi_xMn_yCo_zO₂ (NMC) cathodes. The experimental procedure started with discharging, dismantling the battery, and removing the aluminum foil, followed by the leaching of cathode material before precipitating the lithium phosphate from the solution. In the leaching stage, the parameters to optimize the process were studied. The results showed that the lithium leaching efficiency could be achieved at 96.10% using 2 M H₂SO₄, 8 vol.% H₂O₂, 40 g/L pulp density, and 4 hrs at 70°C. The final precipitate product of 98.98% purity of Li₃PO₄ was recovered from the solution using Na₂HPO₄ under the experimental condition.

Abstract: For the recycling paper process, the main problem is a high residual ink left on the paper, affecting the recycled paper's quality. Especially for laser-printed paper, ink strongly interacts with the paper fiber. A conventional chemical deinking has been used to remove laser ink with a high deinking efficiency but a low yield of recycled paper pulp. Recently, enzymatic deinking has gained attention due to its friendly environment. However, a complex procedure is required, and ink removal efficiency is lower than the conventional method. This research aims to simplify a chemical deinking process by decreasing reaction time, optimizing chemical components, and reducing experimental steps. Without pulping step, the laser-printed paper sheet was immersed in the chemical solution for a specific time, and the ink was removed by water spray. Results revealed that the chemical solution containing 1.5% sodium hydroxide, 2% sodium silicate, 1% hydrogen peroxide, and 0.3% tween-80 with a reaction time of 5 min at 60°C gave the highest paper yield of 97.3% and the lowest dirt count of 89.0 mm²/m². The final product was still in the form of a paper sheet.