• Journal of the Korean Recycled Construction Resources Institute
• /
• v.5 no.4
• /
• pp.353-358
• /
• 2017

The aim of this research is providing a fundamental idea on reducing viscosity of high performance cementitous materials. In rheological aspect, to determine the fluidity of the cementitious materials, both yield stress and viscosity should be controlled. For the high performance cementitious materials with low water-to-binder ratio and high volume fraction, it was difficult to reduce the viscosity with superplasticizer while reducing yield stress was relatively easy. Hence, in this research, with the goal of reducing viscosity of the cementitious materials, both ways of reducing viscosity were suggested: achieving proper combination of powder conditions, and adding low-viscosity typed water reducer. First, by replacing various byproduct powders, specifically, raw coal ash and wasted limestone powder showed favorable results on reducing viscosity of the cement paste. Regarding the low viscosity typed superplasticizer, it showed a good performance on reducing viscosity comparing with generic superplasticizer. Therefore, based on the results of this research, it is expected to provide a fundamental idea on reducing viscosity of cementitious materials by various methods.

• Journal of the Korea Concrete Institute
• /
• v.23 no.2
• /
• pp.225-233
• /
• 2011

The volume change in concrete takes place with changes in temperature and water content immediately after concrete casting. In the early age stage, the thermal and drying shrinkages can cause cracks that are very crucial to the durability of concrete. It was reported that when the cement with lightly-burnt MgO powder was used, the shrinkage of concrete can be reduced. This study investigates fundamental properties of cement composites with lightly burnt MgO powder by performing various experiments. The stability test results verified that MgO powder in cement composites does not cause any abnormal expansion. Also, the hydrate product analysis results obtained from MgO cement paste showed that MgO powder reduces the shrinkage at the longterm ages. In addition, the cement composites containing the proper amount of MgO powder could improve compressive strength. Finally, the shrinkage reduction from using MgO powder can be optimized by increasing MgO replacement level and curing temperature.

• Proceedings of the Korea Air Pollution Research Association Conference
• /
• 1998.04a
• /
• pp.146-147
• /
• 1998

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.9 no.1
• /
• pp.75-84
• /
• 2021

In this study, the correlation between cement quality(chemical composition, mineral composition, and compressive strength) and amount of waste alternative fuels used in the cement manufacturing process and was investigated. Cement manufacturing facility using coal, soft plastics(plastics that are easily scattered by wind power, such as vinyls), hard plastics(plastics that do not contain foreign substances, waste rubber, PP, etc.) and reclaimed oil was analised. Data was collected for 3 years from 2017 to 2019 and let the amount of fuels used as an independent variable and cement quality data as a dependent variable. As a result, depending on the type and quality of the alternative fuel has not a significant effect on the chemical composition(Cl and LSF) and mineral composition(f-CaO, C3S contents). Contrary to the concern that the compressive strength of cement would decrease, there was a significant positive correlation between amount of alternative fuel used and cement compressive strength.

• Cement
• /
• s.192
• /
• pp.39-47
• /
• 2011

최근 온실가스 감축과 기후변화 그리고 녹색성장에 대한 관심증대와 더불어 시멘트 분야의 연구 생산분야는 천연자원 사용량을 줄이고, 소성공정을 도입하지 않은 새로운 개념의 무기바인더가 다시 고개를 들고 있다. 다른 용어로는 비소성, 무시멘트 등으로 표현되기도 하는데, 광의의 개념으로 보면 알칼리 활성화제를 사용한 비소성 무기결합재인 지오폴리머가 바로 그것이다. 지오폴리머 결합재는 1957년 우크라이나의 토목공학회에서 개발한 알칼리 활성 슬래그시멘트에 기원을 두고 있고, 1970년대 말 프랑스의 다비도비치에 의해 지오폴리머라는 용어가 처음 사용되기 시작했다. 알칼리 활성 무기결합재(Alkali-activated inorganic binder)의 정의이다. Alkali-activated inorganic binder는 원래는 결합능력이 없던 재료에 대해서 Alkali-activating 용액을 첨가했을 때, 시멘트처럼 결합능력을 가지게 되는 모든 종류의 결합시스템을 말한다. 국내에도 이미 2000년 초부터 지오폴리머의 개념을 도입한 제품이 상업화되어 오랫동안 품질검증을 거쳐 안정성이 확인되고 있다. 최근에 다시 전남대가 그 동안의 연구성과를 발 빠르게 중소기업에 기술 이전하여 소위 무시멘트 시대에 진입하는 분위기이다. 지난 9월 동아에스텍(주)과 조인트벤처 설립을 위해 손을 잡았고, 사업화가 곧 진행될 것으로 보인다. 이를 계기로 국내에도 무시멘트회사가 본격적으로 등장하게 된 것이다. 따라서 본 고는 무시멘트의 개념을 잘 표현한 문헌으로 일본콘크리트공학 연차논문집, 2010년 1월호를 번역 요약 발췌한 것이다.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.10 no.3
• /
• pp.227-234
• /
• 2022

In this study, the rheological properties of cement paste composites applied with carbon-based nano-materials were experimental analyzed. Flow table and rheological properties, compressive strength were measured in the cement paste using graphene oxide asqueous solution and carbon nanotube aqueous solution. When carbon nano-materials was mixed in an aqueous solution, flow decreased and plastic viscosity and shear stress were increased. In particular, graphene oxide rapidly increased the plastic viscosity and shear stress. In the case of carbon nanotube aqueous solution, when less than 0.2 % was mixed, the increase rate was low compared to graphene oxide. This is because the specific surface area of graphene, which is in the form of a plate, is large. The compressive strength showed a small amount in strength increase when graphene mix, and CNT had a strength about 112 % of OPC. Carbon-based nanomaterials, is considered that CNT are suitable more to be used construction materials. However, extra studies on the surfactant to be used for mixing proportion and dispersion will be needed.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.10 no.3
• /
• pp.252-260
• /
• 2022

In Korea, low-quality kaolin has significantly greater reserves and superior economic efficiency than high-purity kaolin. However, the utilization is low because it does not match the demand conditions of the market, and it is difficult to find a suitable source of demand. The purpose of this study is to derive the possibility and optimal calcination temperature of domestic low-quality kaolin that can be used as a raw material for limestone plastic clay cement (LC³). Isothermal calorimetry, X-ray diffraction analysis, Thermogravimetric Analysis, and compressive strength tests were conducted to evaluate hydrate generation and mechanical properties of LC³ paste according to calcination temperatures (600 ℃, 700 ℃, 800 ℃, 900 ℃). As a result, although 50 % of the clinker was replaced, the domestic low-quality kaolin clay produced calboaluminate hydrate and C(A)SH from the 3rd day of hydration, showing almost equal or higher strength to OPC, and there was a big difference in strength depending on the firing temperature.

• Korean Journal of Mineralogy and Petrology
• /
• v.33 no.4
• /
• pp.407-417
• /
• 2020

The capacity of the designated landfill site for asbestos-containing waste is approaching its limit because the amount of asbestos-containing slate is increasing every year. There is a need for a method that can safely and inexpensively treat asbestos-containing slate in large capacity and at the same time recycle it. A cement kiln can be an alternative for heat treatment of asbestos-containing slate. We intend to develop a pilot scale device that can simulate the high temperature environment of a cement kiln using a high temperature plasma reactor in this study. In addition, this reactor can be used to inactivate asbestos in the slate and to synthesize one of the minerals of cement, to confirm the possibility of recycling as a cement raw material. The high-temperature plasma reactor as a pilot scale experimental apparatus was manufactured by downsizing to 1/50 the size of an actual cement kiln. The experimental conditions for the deactivation test of the asbestos-containing slate are the same as the firing time of the cement kiln, increasing the temperature to 200-2,000℃ at 100℃ intervals for 20 minutes. XRD, PLM, and TEM-EDS analyses were used to characterize mineralogical characteristics of the slate before and after treatment. It was confirmed that chrysotile [Mg3Si2O5(OH)4] and calcite (CaCO3) in the slate was transformed into forsterite (Mg2SiO4) and calcium silicate (Ca2SiO4), a cement constituent mineral, at 1,500℃ or higher. Therefore, this study may be suggested the economically and safely inactivating large capacity asbestos-containing slate using a cement kiln and the inactivated slate via heat treatment can be recycled as a cement raw material.

• Journal of the Korean Ceramic Society
• /
• v.11 no.4
• /
• pp.5-18
• /
• 1974

본 연구에 있어서는 연료유의 연소에 의한 내화물의 부식을 연구하기 위하여 시멘트소성용 회전가마, 보일러 및 판유리제조용 탱크가마에 쓰이는 여러 내화물을 짤라서 그 가운데에 구멍을 파고 중유재의 주성분인 V2O5, Na2CO3, Fe2O3, Fe 및 황산철을 미리 그 구멍속에 넣어 응용 확산시킨 다음 이들을 그들의 상용온도인 145$0^{\circ}C$로 황 함유량이 다른 연류유로 소성하여 얻은 결과는 다음과 같다. 일반적으로 5산화 바나듐-알루미나, 고알루미나질 및 염기성 내화물; 산화나트륨-고알루미나질, 실리마나이트질 및 염기성 내화물은 2%미만의 황 함유 연류유소성에 의하여 부식이 적고 3.5%이상의 황하유 연료유소성시는 황에 의하여 대개가 침식을 당하였다. 무수 아황산 분위기속에서 규산알루미늄 및 구석계의 내화점토질내화물은 산화철이 환원되어 색이 연해지고 고알루미나질 벽돌은 색이 짙어지는 경향이 있고 산화철은 황산철로 변하여 풍화의 원인이 되어 침식을 당하게 되었고, 소성시간이 길면 길수록 부식은 증가하고 황산소다보다 탄산소다에 의하여 훨씬 더 많이 부식을 당하였다.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.11 no.1
• /
• pp.9-15
• /
• 2023

The cement is a typical CO₂ emission industry. Manufacturing process improvements and increased use of alternative materials are needed to reduce energy consumption and CO₂ emissions. This study confirmed the basic characteristics of cement hydration by sintering CAF at low temperature as a CO₂ adsorbent material. For the hydration product of the synthetic CAF, crystal phase analysis, porosity, and structural images were confirmed, and the compressive strength was measured. The replacement rate of SCAF was 10, 20, and 100 %, and the compressive strength tended to decrease as the replacement rate increased. In addition, when the SCAF substitution rate is 100 %, the hydration products of the early age are calcium aluminum oxide hydrate (Ca₃Al₂O₆ x H₂O) and calcium iron hydroxide (Ca₃Fe(OH)₁₂), and at substitution rates of 10 and 20 %, CAF compounds other than general cement hydrates brownmillerite was observed. As for the porosity, the pore size increased and the porosity increased with the increase of the replacement ratio. As a result of this study, CAF manufactured by low-temperature sintering seems to be difficult to use alone and general curing for utilization as a CO₂ adsorbing material.