• Land and Housing Review
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• v.14 no.4
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• pp.121-129
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• 2023

In this study, we attempted to reduce CO₂ generated during manufacturing by replacing limestone (CaCO₃), a carbonate mineral used to produce cement clinker, with a decarbonated raw material to which CO₂ is not bound. The raw material for decarbonization was cement paste attached to waste concrete, among various industrial by-products. Waste concrete has cement paste adhered to the aggregate, which cannot be separated efficiently by general crushing and grinding methods. Peeling and grinding methods effectively remove only the cement paste without damaging the original aggregate. The abrasion time, steel ball type, and steel ball ratio were selected as effective factors for Abrasion. An optimal abrasion experiment was conducted to produce waste concrete fine powder containing decarbonated CaO as a cement clinker raw material through an experimental design method. The experiment revealed that the optimal conditions for producing waste concrete fine powder were an abrasion time of 7 minutes, a steel ball size for pulverization of 8 mm, and a steel ball ratio for pulverization of 0.6.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.8
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• pp.909-914
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• 2007

Fluorine compounds are the essential chemicals for wet processes of semiconductor and LCD production line. Problems of conventional treatments for fluoride wastewater are their high operation costs and low fluoride removal capacity. In this study, cement paste containing various Ca-bearing hydrates such as portlandite, calcium silicate hydrate(CSH), and ettringite was investigated for fluoride removal. The objectives of this study are to assess the feasibility of using cement paste cured mixture of cement and water as an alternative agent for treatment of fluoride wastewater and to investigate fluoride removal capacity of the cement paste. The performance of cement paste was comparable to that of lime in the kinetic test. In column experiment where the effluent fluoride concentrations were below 0.5 mg/L. Then the leached calcium reached the maximum level of 800 mg/L. The nitrate reduced to the level of less than 10 mg/L. Nitrate in the wastewater was exchanged with interlayer sulfate of these cement hydrate LDHs. Phosphate concentration could be reduced to 10 mg/L by forming calcium phosphate. These results indicate that the cement paste generally has advantageous characteristics as an economical and viable substitute for lime to remove fluoride.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.126-133
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• 2019

This study intended to manufacture high quality cement, such as solving the quality problem of cement which has been emerging recently, along with improving grinding efficiency. To this end, the synthesis of melamine-functional pulverizing agents and the physical properties of cement applying them were reviewed and the reaction was carried out by dividing the melamine airborne compound into three stages of polymerization using methylation, sulfonation, and acid catalyst to improve the crushing efficiency of cement clinker and the physical properties of manufactured cement. The obtained melamine type copolymer was applied to the grinding process of cement clinker. And it's grinding efficiency and compressive strength were compared with DEG(diethylene glycol) and TIPA(triisopropanol amine). When it comes to the grinding efficiency, by lowering surface energy with stable adsorption from organic polymer to cement particles, the fineness showed 4-6% up. In the meantime, the compression strength hiked 30% from its initial strength compared to the conventional DEG. At the age of 28days, the strength showed approximately 13% improvement. Therefore, it is confirmed that the overall quality has been elevated in comparison with the conventional one.

• Journal of the Korean Ceramic Society
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• v.41 no.11
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• pp.819-825
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• 2004

The characteristic analysis of cement clinker using light microscope can evaluate not only the quality of cement but also making process. Thus this study analyzed clinkers having different burning conditions by reflective light microscope. As heating and cooling rates is decreased, alite and belite minerals grew and especially cooling rate had an effect on the growth of belite. Futhermore as the retention time in max. temperature got longer by twenty minutes, alite and belite minerals grew more about 5 $\mu\textrm{m}$. In the case of temperature 1400$^{\circ}C$ in max, the size of belite was suitable but alite was not suitable with the size of 10～15 $\mu\textrm{m}$.

• Resources Recycling
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• v.29 no.6
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• pp.88-97
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• 2020

In this study, the selected waste plastic waste logistics used for cement sintering were classified into two types through the process of sorting and crushing, analyzing the characteristics of each, and analyzing the correlation of the strength after cement manufacturing. The experimental variables were classified into soft and hard waste plastic waste, and the correlations between calorific value, chlorine, and moisture were analyzed. In addition, some of each waste was selected and melted, and the basic characteristics were evaluated by analyzing the structure and calorific value. The results of the experiment showed that it was evaluated that it is suitable to obtain a heat source by separating soft waste plastic wastes and sintering them with materials having similar properties. As a result of examining the wastes by strength after cement manufacturing, it was analyzed that the use of hard plastics greatly contributes to the compressive strength on the 1st and 28th, and the use of soft plastics contributes to the compressive strength on the 28th. However, these characteristics are evaluated by collecting only a part of the waste, and since the deviation of the waste occurs, continuous management is required, and a follow-up study on the environmental problems caused by the use of waste is required.

• Clean Technology
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• v.5 no.2
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• pp.13-23
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• 1999

The unique method for evaluating the environmental impact, which is restricted to use in BS7750, was performed to determine the priority for reducing environmental loads in the cement process. Mass balance in the unit process was achieved, it was utilized to introduce the matrix method which are composed of two different evaluation's criteria by occurrence possibility and by occurrence results. The purpose of this paper is first to explain the matrix method in the practical plant and secondly to show the successful examples of enviromental improvement. Conclusively, the seriousness of environmental impact could be quantified in several different unit processes and suggested some progressive results obtained after process improvement.

• Resources Recycling
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• v.30 no.1
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• pp.35-43
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• 2021

In this study, Na2SO4 and KCl reagents were used to synthesize K2SO4 as a basic study for recycling byproducts generated during the manufacture of steel and cement. The mole ratio of Na2SO4 to KCl, the saturation of the solution, and the stirring temperature were controlled to derive the optimal manufacturing conditions. The microstructure and crystallinity of the materials prepared were evaluated using scanning electron microscopy and X-ray diffraction analysis. Pure K2SO4 was obtained when the mole ratio of Na2SO4 to KCl was 1:6-18, the saturation of the solution was less than 160%, and the stirring temperature was 20℃, 50℃. The optimal manufacturing conditions to maximize the crystallinity and yield of K2SO4 while minimizing the energy consumption were 1:6 mole ratio of Na2SO4 to KCl, 140% saturation of the solution, and 20℃ stirring temperature.

• Resources Recycling
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• v.5 no.4
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• pp.25-31
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• 1996

The wastes ot l~mestone mines have been cause the extrar.ngance of the valuablz m e r a l s and destruction of the environment. Therefore, \\-c tied ta separation of calcite illid clay from the limestone mine wastes by rotntmg screen type separator made by ourselves in order to recyding such us a raw matcriala for cement maimfacture. CaO amtents in the separated coarse products increased from 37.36 wt% to 42+2 wt% at the condition ihat water content in wastes was lzss than 6wt%, the passing time of specimen in &amber was 15 semnds and the rotation speed was 6OLl qm. A process in order lo separate wastes effectively to having wide range aI part~dcs ize was cstablishcd and CaO contents of coarsc products through this process increased to 46.85 wt%. Tbis rcsult is insuEiicient to directly rcusing as a raw malerials for cement. However, it is supposed that coarse products would be able to be reuscd as a raw materials uf cement, if only it rs sclected dolomite in wastes, and really it may be possible in fields Othenvise, undcrsize products(less than 20 mm) would be able to recycling as a raw of cement bccause chcmicrl campasitions of thosc is kept almost constant v&cs on the overall process.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.11-17
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• 2013

The use of wasted concrete can settle the environmental pollution and shortage of natural aggregate. However, recycled aggregate includes substantial amount of cement paste, so that these aggregates are more porous, and less resistant to mechanical actions than natural aggregates. Recently, the new manufacturing processes of high quality recycled aggregates were suggested such as heating. In this paper, for the purpose of manufacture of high quality recycled aggregates, the heating processes was considered to the existing process of recycled aggregates. To find the optimum process, the experiment was performed through the statistical design of experiment. The heating temperatures of 4 levels (300, 450, 600 and $750^{\circ}C$) and heating duration time (5, 20, 40, 60minute) were main experimental variables. Through the test results, it was found that the optimum manufacturing condition of coarse recycled aggregate was evaluated to be $600^{\circ}C$ and 40minute.

• Resources Recycling
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• v.25 no.4
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• pp.23-31
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• 2016

It was found that there was no problem in recycling by-products (waste rock and tailings) from Yangyang iron mine themselves through matter conversion because they are not hazardous according to results of KSLT method. In case of using tailings as sub-materials of cement, it recommended the use of less than 3% tailings dosage not to exceed 0.6% of total alkali ($R_2O$) content based on standard quality of portland cement (KS L 5201). Non sintered eco-brick corresponding to class 1 quality of recycled clay brick (KS I 3013) can replace 15% of cement with tailings and 100% of general fine aggregate with waste rock from iron mine. As mentioned above, recycling the by-products (waste rock and tailings) as sub-materials of cement and non sintered eco-brick could gain both environmental and economic benefits, that is, reduction of scale and maintenance cost of tailing ponds, decrease of energy use and $CO_2$ emission.