• Resources Recycling
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• v.29 no.1
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• pp.43-52
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• 2020

The objectives of this study were to identify the optimal mix of foam concrete with the low-strength and high-flow for the repairing ground subsidence situation emergently by utilizing a large amount of industrial by-products and evaluate the possibility by applying it to the site. The factors of the experiment were the mixing ratio of mixing water and a foaming agent and the mixing ratio of foam over paste volume. The optimal mix identified by the experiment was applied to the field and basic properties were evaluated. The results of the experiment showed that the optimal mixing ratio of mixing water and the foaming agent was 10%. Moreover, when the mixing ratio of pre-foam over paste volume was 170%, it satisfied the target. However, to ensure stable quality when applying to the field, the foam mixing ratio was set 140% for the field application. The field application test of foam concrete with the low-strength and high-flow using an eco-friendly binder satisfied all target performances. Therefore, the possibility of using it as a mixture and construction method for a ground repair system is confirmed. However, there was a quality deviation between the upper part and the lower part due to the separation between foam and paste. Consequently, further studies are needed to improve it.

• Resources Recycling
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• v.29 no.4
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• pp.3-14
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• 2020

Titanium sponge is industrially produced by the Kroll process. In order to understand the importance of the emerging smelting and recycling process, it is necessary to review the conventional production process of titanium. Therefore this paper provides a general overview of the conventional titanium manufacturing system mainly by the Kroll process. The Kroll process can be divided into four sub-processes as follows: (1) Chlorination of raw TiO₂ with coke, by the fluidized bed chlorination or molten salt chlorination (2) Magnesium reduction of TiCl₄ and vacuum distillation of MgCl₂ and Mg by reverse U-type or I-type with reduction-distillation integrated retorts (3) Electrolysis process of MgCl₂ by monopolar cells or multipolar cells to electrolyze into chlorine gas and Mg. (4) Crushing and melting process in which sponge titanium is crushed and then melted in a vacuum arc furnace or an electron beam furnace Although the apparatus and procedures have improved over the past 80 years, the Kroll process is the costly and time-consuming batch operation for the reduction of TiCl₄ and the separation of MgCl₂.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.642-649
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• 2021

Energy saving standard for buildings are strengthened, the application of exterior insulation finishing system and thickness of insulation materials are increasing. Most buildings with exterior insulation finishing system is applied organic insulating material. Organic insulating material have workability, economic feasibility, reduction in construction cost, and excellent thermal insulation performance. However, Organic insulating material is very vulnerable to heat, so when a fire occurs, rapid fire spread and toxic gas are generated, causing many casualties. Inorganic insulating material can be non-combustible performance, but it is heavy and has low thermal insulation performance. Mineral wool has higher thermal insulation performance than other types of inorganic insulating material, but mineral wool is disadvantageous to workability and vulnerable to moisture. Glass bubble are highly resistant to water and chemically stable substances. In addition, the density of the glass bubble is very low and the particles are spherical, fluidity is improved by the ball bearing effect. Glass bubbles can be used with cement-based ino rganic insulating material to impro ve the weight and thermal insulatio n perfo rmance o f cement-based inorganic insulation. This study produced a inorganic insulating materials were manufactured using cement-based materials and glass bubble. In order to evaluate the insulation performance and flame retardant performance of cement-based super light-weight inorganic insulating materials using with glass bubble, insulation performance or flame retardant and non-combustible performance were evaluated after manufacturing insulating materials using micro cement and two types of glass bubbles. From the test result, Increasing the mixing ratio of glass bubbles improved the insulation performance of cement-based super light-weight inorganic insulating materials, and when the mixing ratio of glass bubbles was 10%, it sho wed sufficient flame retardant and no n-co mbustible perfo rmance.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.478-482
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• 2021

In this paper, methods for manufacturing shielding concrete by recycling steelmaking slag discarded as industrial waste and measuring the shielding effectiveness of the shielding concrete were studied. By comparing the result of shielding effectiveness measurement of this concrete block with shielding effectiveness measurement of the structure constructed with this concrete, the measurement system for measuring shielding effectiveness of the concrete block was verified. The size of the concrete stru ctu re is 2.9 × 2.9 × 3.4m and the concrete block is 0.3 × 0.3 × 0.2m. The frequ ency band u sed for mesu rement is 600MHz - 2GHz, the types of concrete u sed to measu re the shielding effectiveness are general concrete and concrete containing electric arc furnace oxidizing slag. In the case of the concrete structure, reinforcing rebars are installed at intervals of 15cm for stru ctu ral safety, as the frequ ency increase, the electromagnetic wave properties of rebars gradu ally decreased, there was a slight difference in the measurement results. In conclusion, the measurement result of shielding effectiveness of the concrete block is similar to the result of the concrete structure. It is thought that it can be sufficiently utilized for electromagnetic wave engineering design, and the concrete shielding effectiveness measurement system using standard specimens was verified.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.553-560
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• 2021

In this study, cement clinker using a pure sample and clinker using 7% coal ash were sintered at a temperature of 1050~1500℃. Changes in the content of cement minerals and changes in microstructure by sintering temperature were reviewed. The application of coal ash as a raw material for cement clinker was applicable as a source of Al₂O₃ and SiO₂. At a sintering temperature of 1350℃ or higher, the cement clinker applied with coal ash showed the same level of mineral content as compared to the cement clinker applied with pure raw material. The microstructure also showed a similar state, confirming that coal ash can be used as a raw material for cement. In XRD-Reitveld analysis, a maximum amount of Belite was produced at 1250℃. The conversion from Belite to Alite was observed from 1350℃. From 1350℃, the interstitial phase and the mineral phase presumed to be alite were distinguished. It was clearly distinguished from 1400℃. As the sintering temperature increased, the shape and boundary of the crystal phase became clear, and the size of the crystal phase was also increased.

• Resources Recycling
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• v.30 no.1
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• pp.44-52
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• 2021

This study investigated the effect of the type of alkaline precipitant used on the synthesis of lithium hydroxide by examining the behavior of lithium hydroxide produced using lithium sulfate recovered from a waste lithium secondary battery as a raw material. The double-replacement reaction (DRR) process was used to remove the impurities contained in the lithium salt precursor of lithium sulfate and to improve the efficiency of the synthesis of lithium hydroxide. The experiment was conducted by control the molar ratio of the precursor ([Li]/[OH]), the reaction temperature, and the composition of the alkaline precipitant (KOH, Ca(OH)2, Ba(OH)2) used for the production of highly-crystalline lithium hydroxide. A secondary solid-liquid separation was performed following the reaction to remove the impurities generated, and the purified aqueous solution of lithium hydroxide was evaporated to remove the moisture and obtain the product as a powder. The crystallinity and synthesis behavior of the product were examined.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.357-364
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• 2018

Fly ash is a material used as a concrete admixture. When fly ash is used for concrete manufacturing, it is expected to improve the performance such as reduction of cement usage and increase of chemical resistance. However, fly ash have some problems such as unburned carbon content and amorphous film on the surface of fly ash particles. When concrete is manufactured using fly ash containing a large amount of unburned carbon, there is a problem that the slump is lowered due to adsorption of AE agent. In addition, the amorphous film on the surface of the particles prevents the reactive substances from leaching out of the fly ash. Therefore, a method of surface treatment of fly ash using plasma has been studied to remove such unburned carbon and amorphous films. However, plasma has the problem that $O_3$ is generated when $O_2$ is used as an active gas. $O_3$ is a harmful substance and adversely affects the health of the experimenter. In this study, the surface of fly ash was treatment by arc discharge. Experimental results show that the unburned carbon is removed when the surface of fly ash is treatment by arc discharge and the amorphous film was broken and the reactivity was improved. Therefore, it is considered that arc discharge can treatment the surface of fly ash and improve the quality of fly ash.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.289-296
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• 2018

In this study, we evaluated the feasibility and performance of LCD waste glass as a replacement for cement by using LCD waste glass powder which is generated from manufacturing process due to development of LCD industry. Experiments were carried out by replacing 10% and 20% cement of LCD waste glass with particle size of $12{\mu}m$ of LCD waste glass with OPC and particle size of $5{\mu}m$, respectively. Through experiments, basic properties, mechanical properties and durability of concrete were evaluated. Experimental results show that the compressive strength is high at 10% replacement ratio compared to 20%. The lower the particle size, the higher the strength. The durability test evaluated the chloride penetration performance through the chloride ion diffusion coefficient. The higher the substitution rate and the smaller the particle size, the lower the chloride ion diffusion coefficient and the better the OPC than the all substitution rate. As a result, LCD waste glass concrete with low granularity and proper replacement ratio is considered to be advantageous for durability under salt environment.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.1
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• pp.22-28
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• 2019

Cement is a basic material for the construction industry and it requires high temperature sintering when manufacturing cement. $CO_2$ emissions from raw materials and fuels are recognized as new environmental problems and efforts are underway to reduce them. Techniques for reducing $CO_2$ in concrete are also recommended to use blended cement such as blast furnace slag or fly ash. In addition, the construction waste generated in the dismantling of concrete structures is recognized as another environmental problem. Thus, various methods are being implemented to increase the recycling rate. The purpose of this study is to utilize the inorganic raw materials generated during the dismantling of the structure as a raw material for the low carbon type cement binder. Such as, waste concrete powder, waste cement block, waste clay brick and waste textile as raw materials for low carbon type cement binder. From the research results, low carbon type cement binder was manufactured from the raw material composition of waste concrete powder, waste cement block, waste clay brick and waste textile.

• Korean Chemical Engineering Research
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• v.57 no.3
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• pp.413-419
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• 2019

In the recent, as a world demand of energy resources has been transformed from fossil fuels to hydrogen-based clean energy resources, a huge attention has been attracted to increase the performance and decrease a production cost of core materials in fuel cell technology. The utilization of reinforced composite membranes as electrolytes in the polymer electrolyte membrane fuel cells can reduce the use of high cost perfluorosulfonic acid (PFSA), mitigate the cell impedance, and improve the dimensional stability as well as the interfacial stability, giving rise to achieve both an improved performance and a reduction of production costs of the fuel cell devices. In this study, we investigate the effects of physical characteristics and cell performances according to the various ionomer solvents in the solution based manufacturing process of reinforced composite electrolyte membrane.