• Journal of the Korea Organic Resources Recycling Association
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• v.28 no.4
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• pp.15-22
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• 2020

The landfill gas produced in landfill is generally made up of methane(CH4) and carbon dioxide(CO2) of more than 90%, with the remainder made up of hydrogen sulfide(H2S). However, separate pre-treatment facilities are essential as hydrogen sulfide contained in landfill gas is combined with oxygen during the combustion process to generate sulfur oxides and acid rain combined with moisture in the atmosphere. Various desulfurization technologies have been used in Korea to desulfurize landfill gas. Although general desulfurization processes apply various physical and chemical methods, such as treatment of sediment generation according to the CaCO3 generation reaction and treatment through adsorbent, there is a problem of secondary wastes such as wastewater. As a way to solve this problem, a biological treatment process is used to generate and treat it with sludge-type sulfide (S°) using a biological treatment process.In this study, as a basic study of technology for utilizing the biological treatment by-products of hydrogen sulfide in landfill gas, an experiment was conducted to use the by-product as a mixture of concrete. According to the analysis of the mixture concrete strength of sulfur products, the mixture of sulfur by-products affects the strength of concrete and shows the highest strength value when mixing 10%.

• Journal of the Korea Concrete Institute
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• v.18 no.5 s.95
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• pp.687-693
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• 2006

The Stone Powder Sludge(below SPS) is the by-product from the process that translates stone power of 8mm under as crushed fine aggregate. It is the sludge as like cake that has average particle size of $7{\mu}m$, absorbing water content of 20 to 60%, and $SiO_2$ content of 60% over. Because of high water content of SPS, it is not only difficult to handle, transport, and recycle, but also makes worse the economical efficiency due to high energy consuming to drying. This study is aim to recycle SPS as it is without drying. Target product is the lightweight foamed concrete that is made from the slurry mixed with pulverized mineral compounds and foams through hydro-thermal reaction of CaO and $SiO_2$. Although in the commercial lightweight foamed concrete CaO source is the cement and $SiO_2$ source is high purity silica powder with $SiO_2$ of 90%, we tried to use the SPS as $SiO_2$ source. From the experiments with factors such as foam addition rate and replacement proportion of SPS, we find that the lightweight foamed concrete with SPS shows the same trends as the density and strength of lightweight foamed concrete increases according to decrease of foam addition rate. But in the same condition, the lightweight foamed concrete with SPS is superior strength and density to that with high purity silica. This trends is distinguished according to increase of replacement proportion of SPS, also the analysis of XRF shows that the hydro thermal reaction translates SPS to tobermorite. Although SPS has low $SiO_2$ contents, the lightweight foamed concrete with SPS has superior strength and density, because it reacts well with CaO due to extremely fine particles. We conclude that it is possible to replace the high purity silica as SPS in the lightweight foamed concrete experimentally.

• Journal of the Korea Concrete Institute
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• v.27 no.2
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• pp.95-102
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• 2015

In this paper, the effects of sodium hydroxide (NaOH) and aluminum potassium sulfate ($AlK(SO_4)_2{\cdot}12H_2O$) dosage on strength properties were investigated. For evaluating the property related to the dosage of alkali activator, sodium hydroxide (NaOH) of 4% (N1 series) and 8% (N2 series) was added to 1~5% (K1~K5) dosage of aluminum potassium sulfate ($AlK(SO_4)_2{\cdot}12H_2O$) and 1% (C1) and 2% (C2) dosage of calcium oxide (CaO). W/B ratio was 0.5 and binder/ fine aggregate ratio was 0.5, respectively. Test result clearly showed that the compressive strength development of alkali-activated slag cement (AASC) mortars were significantly dependent on the dosage of NaOH and $AlK(SO_4)_2{\cdot}12H_2O$. The result of XRD analysis indicated that the main hydration product of $NaOH+AlK (SO_4)_2{\cdot}12H_2O$ activated slag was ettringite and CSH. But at early ages, ettringite and sulfate coated the surface of unhydrated slag grains and inhibited the hydration reaction of slag in high dosage of $NaOH+AlK(SO_4)_2{\cdot}12H_2O$. The $SO_4{^{-2}}$ ions from $AlK(SO_4)_2{\cdot}12H_2O$ reacts with CaO in blast furnace slag or added CaO to form gypsum ($CaSO_4{\cdot}2H_2O$), which reacts with CaO and $Al_2O_3$ to from ettringite in $NaOH+AlK(SO_4)_2{\cdot}12H_2O$ activated slag cement system. Therefore, blast furnace slag can be activated by $NaOH+AlK(SO_4)_2{\cdot}12H_2O$.

• The korean journal of orthodontics
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• v.26 no.4
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• pp.455-467
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• 1996

This study was designed to evaluate the expression of type I collagen in periodontal tissue during the experimental movement of rat incisors. Twenty-one Sprague-Dawley rats were divided into a control group(3 rats), and experimental groups(18 rats) where a force(75g) from helical springs across the maxillary incisors was applied. Experimental groups were sacrificed at 12 hours, 1, 4, 7, 14 and 28 days after force application, respectively. And tissue slides of control and experimental groups were studied histologically and immunohistochemically by LSAB(Labelled streptavidine Biotin) immunohistochemical staining for type I collagen. The results were as follows: 1. Until 28-day after force application, periodontal fibers were strectched on the tension side, and compressed in pressure side, and the arrangement of periodontal fibers was not recovered by that time. 2. The degree of type I collagen expression in control group was rare in the oral epithelium, predentin, pulp and periodontal ligament, but was mildly positive in osteoblasts, acellular cementum, cementoblasts, intermaxillary suture. 3. At acellular cementum of experimental group, the expression of type I collagen was moderate in 1-day and severe in 7-day, which was maintained until 28-day. 4. Type I collagen was observed in the newly formed fibrous connective tissue and osteoblasts at intermaxillary suture, moderately in 1-day, and severely in 14-day. 5. The tension side of periodontal ligament showed a more positive expression of type I collagen than the pressure side in 4-day. The degree was highest in 7-day and was not differentiated between sides in 14-day. 6. In the side wall of bone matrix on which osteoblasts were attached, type I collagen was expressed severely, especially in 7-day. From the above findings, we could suggest that bone remodeling in tooth movement be intimately related to the cell differentiation and the resulting formation of type I collagen.

• Journal of Periodontal and Implant Science
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• v.34 no.1
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• pp.223-241
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• 2004

The purpose of this present study evaluated the osseous response around Ca-P coated xenogenic bone and compared osteogenic potential of Ca-P coated xenogenic bone to that of combination with type I collagen derived from bovine tendon as a biocompatible binder to prevent migration of bone particle on the repair of calvarial defects in rabbits. To study the effects of Ca-P coated xenogenic bone and collagen on bone healing, four 5-mm-diameter skull defect were made in calvaria with trephine filled with an autogenous bone chip or Ca-P coated xenogenic bone or Ca-P coated xenogenic bone and type I collagen (1:1 mixture by volume) or left empty. The defects were evaluated histologically at 1, 2, 4 and 8 weeks following implantation. Ca-P coated xenogenic bone at the calvarial defects of rabbits showed osteoconductivity at the margin of defect in the early stage of bony healing, but no direct contact with new bone was observed. With time passed by, it was resorbed slowly and showed consistent inflammatory reaction. An additional use of type I collagen derived from bovine tendon improved clinical handling, but no new bone formation was observed histologically. Above all, autogenous bone graft showed most prominent healing in quantity and density of new bone formation. According to this study, the use of Ca-P coated xenogenic bone alone and combination with type I collagen did not showed effective healing in quantity and density of new bone formation.

• Resources Recycling
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• v.32 no.1
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• pp.50-59
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• 2023

The amount of dust generated during the dissolution of scrap in an electric arc furnace is approximately 1.5% of the scrap metal input, and it is primarily collected in a bag filter. Electric arc furnace dust primarily consists of zinc and ion. The processing of zinc starts with its conversion into pellet form by the addition of a carbon-based reducing agent(coke, anthracite) and limestone (C/S control). These pellets then undergo reduction, volatilization, and re-oxidation in rotary kiln or RHF reactor to recover crude zinc oxide (60%w/w). Next, iron is discharged from the electric arc furnace dust as a solid called Fe clinker (secondary by-product of the Fe-base). Several methods are then used to treat the Fe clinker, which vary depending on the country, including landfilling and recycling (e.g., subbase course material, aggregate for concrete, Fe-source for cement manufacturing). However, landfilling has several drawbacks, including environmental pollution due to leaching, high landfill costs, and wastage of iron resources. To improve Fe recovery in the clinker, we pulverized it into optimal -sized particles and employed specific gravity and magnetic force selection methods to isolate this metal. A carbon-based reducing agent and a binding material were added to the separated coarse powder (>10㎛) to prepare briquette clinker. A small amount (1-3%w/w) of the briquette clinker was charged with the scrap in an electric arc furnace to evaluate its feasibility as an additives (carbonaceous material, heat-generating material, and Fe source).

• Journal of Periodontal and Implant Science
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• v.28 no.4
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• pp.577-604
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• 1998

chitosan은 골치유증진 및 골세포의 분화를 촉진하는 것으로 알려진 천연의 생분해성 고분자이다. 이연구에서는 chitosan 및 chitosan/tricalcium phosphate(TCP) 다공성 기질을 제조하여 골이식재 및 조직공학적 골형성을 위한 3차원적 세포배양 지지체로서의 가능성을 평가하고자 하였다. chitosan 용액 및 TCP가 포함된 chitosan 용액을 동결건조함으로써 소공의 크기가 $100-200{\mu}m$인 스폰지형태의 chitosan 및 chitosan/TCP 다공성 기질을 제작하였다. 골이식재로서의 효과를 평가하기 위하여 백서의 두개골 결손부에 제작된 chiosan 및 chitosan/TCP 다공성 기질을 각각 이식하고 2주 및 4주 후에 동물을 희생하여 조직학적으로 치유양상을 관찰하였다. 조직공학적 골형성을 위한 세포배양 지지체로서의 가능성을 평가하기 위하여 백서 태자의 두개골에서 분리된 골아세포를 chitosan 및 chitosan/TCP 다공성 기질에 각각 접종하고 56일간 배양하면서 각 기간 별로 세포수, 염기성 인산효소 활성, 축적된 calcium의 양을 측정하였고 배양된 세포-기질 혼합체를 광학현미경 및 주사전자현 미경하에서 조직학적 관찰을 시행하였다. 백서 두개골결손부에 이식된 chitosan 및 chiosan/TCP 다공성 기질은 별다른 이물반응 없이 자연 분해되면서 신생골조직 내에 매립되었으며 이식하지 않은 대조군에 비해 유의하게 높은 신생골형성 효과를 나타내어 우수한 골전도성이 있음이 확인되었다. 신생골형성 양상이나 형성된 양에 있어서 두 가지 기질간의 유의한 차이는 없었다. 골아세포-기질 혼합체의 배양결과, 접종후 배양 28일 경과 시까지 골아세포수는 지속적으로 증가하다가 이후에는 5 8일까지 성장정도가 둔화되었다. 염기성 인산효소의 활성 및 calcium 축적량은 접종후 배양시간경과에 따라 56일까지 지속적으로 증가하였다. 세포수 및 염기성 인산효소의 활성에서 두 기질간의 유의한 차이는 없었고, calcium 축적량에 있어서는 chitosan/TCP 기질에서 유의하게 높았고 증가속도도 컸다. 배양된 골아세포가 접종된 다공성 기질의 조직학적 관찰결과, 골아세포는 다공성 기질에 잘 부착하여 중층의 형태로 성장하면서 광화된 골기질을 형성함이 관찰되었다. 배양 14일부터 작은 골편형태의 골형성이 기질 표면에 부착되어 관찰되었고, 배양기간이 길어짐에 따라 성장하여 배양 56일째에는 상당한 양의 광화된 골질이 형성됨이 관찰되었다. 배양 56일 경과후의 광화된 골질의 양은 chitosan/TCP 기질에서 더 많았다. 이 연구의 결과, chitosan 및 chitosan/TCP 다공성 기질이 골이식재로서 뿐만 아니라, 조직공학적 골형성에 적용되는 골아세포의 배양을 위한 3차원구조의 세포지지체로 이용되어 골재생술식에 유용한 생체재료로 활용될 수 있음이 확인되었다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.5A
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• pp.307-315
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• 2012

Recently, ultra high performance fiber reinforced concrete (UHPFRC) having over 180 MPa compressive strength and 10 MPa tensile strength has been developed in Korea. However, UHPFRC represents different material properties with normal concrete (NC) and conventional high performance concrete (HPC) such as a high early age autogenous shrinkage and a rapid dry on the surface, because it has a low water-binder ratio and high fineness admixtures without coarse aggregate. In this study, therefore, to propose suitable experimental methods and regulations, and to evaluate mechanical properties at a very early age for UHPFRC, setting, shrinkage and tensile tests were performed. From the setting test results, paraffin oil was an appropriate material to prevent drying effect on the surface, because if paraffin oil is applied on the surface, it can efficiently prevent the drying effect and does not disturb or catalyze the hydration of cement. From the ring-test results, it was defined that the shrinkage stress is generated at the time when the graph tendency of temperature and strain of inner steel ring is changed. By comparing with setting test result, the shrinkage stress was firstly occurred as the penetration resistance of 1.5 MPa was obtained, and it was about 0.6 and 2.1 hour faster than those of initial and final sets. So, the starting time of autogenous shrinkage measurement (time-zero) of UHPFRC was determined when the penetration resistance of 1.5 MPa was obtained. Finally, the tensile strength and elastic modulus of UHPFRC were measured from near initial setting time by using a very early age tensile test apparatus, and the prediction models for tensile strength and elastic modulus were proposed.

• International Journal of Highway Engineering
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• v.13 no.2
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• pp.103-114
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• 2011

Usage of bicycle has been supported the universal reduction of energy consumption and $CO_2$. For the same purpose, new constructions for long length bike roads are planned in Korea. Recently, laboratory tests of physical properties and resistance against environmental loading about optimum mix design of roller compacted concrete, that have advantages of high structural performance by cement hydration and aggregate interlocking, simple construction procedure and low construction cost, are performed for the effective construction of new bike roads. However, properties of roller compacted concrete had different results between laboratory and field tests since it had different compaction method. Also, construction method of roller compacted concrete are not defined for the application of bike roads since it had different demand performance such as thin pavement thickness, low strength and etc with road pavements. Thus, in this experimental research was launched to evaluate the core properties, visual inspection, compaction ratio, water content, thickness reduction rate of roller compaction, skid resistance and roughness by experimental construction about variable mix proportion and compaction method based on laboratory test results. And construction method of roller compacted concrete pavement were suggested for the application of bike roads.

• Journal of the Korea Concrete Institute
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• v.16 no.1 s.79
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• pp.70-78
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• 2004

Although set accelerating agents are used generally in New Austrian Tunneling Method, the standards for test methods and quality of set accelerating agents are not prescribed domestically. In this study, the proprieties of the various standards and the characteristics of set accelerating agents for shotcrete were evaluated. The alkali contents of set accelerating agents based on silicate, aluminate and cement were higher than those of alkali-free ones. From the result, it is thought that the quality control of aggregate should be enhanced and that the number of test cycle of alkali-aggregate reaction should be increased. The setting times of cement paste with set accelerating agents based on silicate and alkali-free ones were different largely with mixing methods. Compressive strength of mortar with set accelerating agents based on silicate, aluminate and cement at one day satisfied the specifications of Korea Concrete Institute. However, the strength ratio compared to control mix at 28 days showed as $50{\~}65\%$ except for the alkali-free set accelerating agents. As a results of setting time and strength test, the establishment of domestic standards that can reflect the characteristics of materials and construction methods of tunnels and that can increase quality of set accelerating agents is required immediately.