• 한국건설순환자원학회논문집
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• 제2권4호
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• pp.297-306
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• 2014

Recently nano-materials are gaining more importance in the construction industry due to its enhanced energy efficiency, durability, economy, and sustainability. Nano-silica addition to cement based materials can control the degradation of the fundamental calcium-silicate-hydrate reaction of concrete caused by calcium leaching in water as well as block water penetration and therefore lead to improvements in durability. In this paper, the influence of synthesized nano silica from locally available rice husk on the mechanical properties and corrosion resistant properties of OPC (Ordinary Portland Cement) has been studied by conducting various experimental investigations. Micro structural properties have been assessed by conducting Scanning Electron Microscopy, Thermo gravimetry and Differential Thermal Analysis, X-Ray Diffraction analysis, and FTIR studies. The experimental results revealed that NS reacted with calcium hydroxide crystals in the cement paste and produces Calcium Silicate Hydrate gel which enhanced the strength and acts as a filler which filled the nano pores present in concrete. Hence the strength and corrosion resistant properties were enhanced than the control.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 봄 학술논문 발표대회
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• pp.166-167
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• 2022

The International Energy Agency(IEA) recommends that intergovernmental agreements reduce CO2 emissions by 2050 to about 50% in 2005 in its report. To realize these demands, it is suggested to actively utilize energy efficiency improvement technology, renewable energy, nuclear power, carbon dioxide capture & storage technology (CCS). In the field of building materials and cement, mineral carbonization technology is widely used. Inorganic by-products applicable to greenhouse gas storage include waste concrete, slag, coal ash, and gypsum. If the Mineral Carbonation Act is used, it is expected that about 12 million tons of greenhouse gases can be immobilized every year. Greenhouse gas immobilization using cement hydrate can be immobilized by injecting carbon dioxide into the hydrated products C-S-H, and Ca(OH)2. In the case of immobilization through concrete carbonization, a carbon dioxide promotion test is used, which is often different from the actual carbon dioxide carbonization reaction. If the external carbon dioxide concentration is abnormally higher than the reality, it is thought that it will be different from the actual reaction. In this study, the carbonation phenomenon according to the concentration and identification of the carbon dioxide reaction mechanism of cement hydrate was to be considered.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.11-16
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• 2002

The production of Portland cement involves maximum use of resources and energy, which leads to destruction of tile ecological environment, raising in serious environmental issues such as acid rain and the greenhouse effect. In order to combat the arising problems associated with Portland cement, it thus is necessary that a non-clinker cement should be developed. In this study, non-clinker cement is produced by blending granulate blast furnace slag with phosphogypsum as main materials, and small amounts of hydrate lime or waste lime as activators. This paper aims to investigate compressive strength according to various condition of mixing ratio, blame, W/C ratio and curing temperature. Compressive strength of non-clinker cement increases continuously according to increase in curing age and blain. Although the compressive strength is fairly comparable to that of OPC in the early curing age, it reaches a higher lever in the later age than that of OPC due to the optimum mixing ratio and the continuous reaction of slag and phosphogypsum. Results obtained from this study have shown that non-clinker cement could be used as a replacement of OPC.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 가을 학술논문 발표대회
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• pp.147-148
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• 2020

In case of high temperature damage such as fire, the durability of concrete is reduced due to the collapse of internal pore tissue. Therefore, in this paper, we are going to analyze the pore structure of cement paste hardening agent using MIP analysis and build up 3D data produced using X-ray CT tomography. The test specimen is made of cement paste from W/C 0.4. As the temperature of heating increased, the amount of air gap and the diameter of air gap in cement paste increased. It is judged that the air gap structure inside cement collapsed due to the evaporation of the hydrate, gel count, capillary water, etc. inside the cement due to the high temperature.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
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• pp.293-296
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• 2003

The purpose of this study is to examine the effect of aluminium sulfate on setting time and compressive strength of cement mortar as focused on formation of ettringite by the reaction between aluminium sulfate and calcium hydrate. The specific parameter was the addition ratio of aluminium sulfate to cement mortar. After specimens made by admixing aluminium of 0~7% by weight of cement, respectively, to cement mixtures, the experimental items such as setting time, compressive strength and heat of hydration in this study were carried out. As a result of this study, it is possible that aluminium sulfate could be added into cement mixture from a standpoint of increasing early compressive strength as considering the setting time and heat of hydration.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2017년도 추계 학술논문 발표대회
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• pp.149-150
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• 2017

It is known that physical and chemical changes of cement hydrates cause problems in the volume stability of concrete. In order to overcome these problems, there is a growing interest in research on mixing technology of cement-based materials and nanomaterials. Among the nanomaterials, carbon nanotubes (CNTs) are attracting attention due to their excellent mechanical properties. The CNTs are made of cylindrically shaped graphene sheets. According to the number of sheets, single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) are classified. Although the SWCNT has superior mechanical properties, the research using MWCNT is vigorous due to the difficulty of marketability and manufacturing, but the research using SWCNT is insufficient. In this study, we investigate the effect of SWCNT on the formation of hydrate of cement paste by observing the microstructure of broken cement paste after measuring the flexural strength of cement paste with SWCNT dispersion.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표회 논문집(I)
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• pp.185-190
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• 1998

Corrosion of steel reinforcement is the most significant factor of deterioration in reinforced concrete structures. Chloride ion is considered one of the most common culprits on the corrosion of steels in concrete. The main objective of this study is understanding behavior of chloride ion in hardened cement pastes at different stages of curing. Cement pastes with water-cement ratio of 0.5 are allowed to hydrate in sealed containers for 28, 70, 180 days. And than pore solution is expressed. It was found that the $Cl^-$ concentrations in pore solution is decreased with increasing curing time in all Nacl addition level, the $OH^-$ concentrations is increased to 70 days but decrease at 180 days in all Nacl addition level. The $Cl^-$/$OH^-$ in pore solution is increased with increasing curing time in all Nacl addition level, however $Cl^-$/$OH^-$ of maximum Nacl addition level(Nacl 0.54% by weight of cement) is under the onset of depassivation level 0.3.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2003년도 학술.기술논문발표회
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• pp.81-87
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• 2003

The purpose of this study is the development of a recycling process to recover the hydrated ability of cement hydrate which accounts for a large proportion of cementitious powder by concrete waste in order to recycle cementitious powder by concrete waste as recycle cement. Therefore, after having theoretical consideration based on the properties of high-heated concrete, we consider the properties of hydration of cementitious powder in hardened mortar under various temperature conditions. As a result of experiment, it is revealed that an effective development of recycling cement is possible since the cementitious powder by concrete waste recovers a hydraulic property during burning at $600^{\circ}C$ or $700^{\circ}C$. And it is shown that the fluidity of mortar decreases rapidly as the burning temperature of recycle cement increases. however, the improved effect of fluidity is predominant if adding the additive such as fly-ash or blast furnace slag.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2005년도 춘계 학술기술논문발표대회 논문집
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• pp.61-64
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• 2005

Recently, there have been many studies about recycling cementitious powder from concrete waste(hereinafter referred to as waste powder), generated after recycle aggregate production. Previous studies showed that when the heating process of waste powder at $700^{\circ}C,\;Ca(OH)_2$ in paste is dehydrated making possible the restoration of hydraulic properties. Recycled cement with hydraulic properties restored is thought to be re-hydrated through the mechanism of hydration, which is almost similar in Portland cement. This clearly suggests that the hydrate of recycled cement is alkali in type. Like in general concrete, if recycled cement is used as a structural material, resistance performance against carbonation or neutralization by $CaCO_3$ in air probably would be most influential to the life of steel-reinforced concrete structure. Thus the purpose of this study is to make an experimental review on chemical properties of recycled cement, manufactured with concrete waste as base material, and investigate the durability of concrete using recycled cement through evaluating the cement s performance of resistance to carbonation in accordance with its accelerating age. Based on its results, further, the study seeks to provide basic information about ways of utilizing recycled cement.

• 한국건축시공학회지
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• 제6권4호
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• pp.61-68
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• 2006

Recently, there have been many studies about recycling cementitious powder from concrete waste(hereinafter referred to as waste powder), generated after recycle aggregate production. Previous studies showed that when the heating process of waste powder at $700^{\circ}C,\;Ca(OH)_2$ in paste is dehydrated making possible the restoration of hydraulic properties. Recycled cement with hydraulic properties restored is thought to be re-hydrated through the mechanism of hydration, which is almost similar in Portland cement. This clearly suggests that the hydrate of recycled cement is alkali in type. Like in general concrete, if recycled cement is used as a structural material, resistance performance against carbonation or neutralization by $CaCO_3$ in air probably would be most influential to the life of steel-reinforced concrete structure. Thus the purpose of this study is to make an experimental review on chemical properties of recycled cement, manufactured with concrete waste as base material, and investigate the durability of concrete using recycled cement through evaluating the cement's performance of resistance to carbonation in accordance with its accelerating age. Based on its results, further, the study seeks to provide basic information about ways of utilizing recycled cement.