• 콘크리트학회논문집
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• 제12권3호
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• pp.11-19
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• 2000

It has been reported that few manufacturers of cement mortar for precast products use chemical and mineral admixture due to the absense of restrictions related to the application of admixture and the poor manufacturing facilities. Therefore, this paper is intended to contribute to the improvement of quality by investigating the properties of cement mortar for precast products using fly ash, blast furnace slag and AE water reducing agent. According to the test results. it was found that the cement mortar products using fly ash and AE water-reducing agent had better qualities than those of ordinary portland cement.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 가을학술발표대회논문집
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• pp.207-208
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• 2023

Concrete bricks and hollow concrete block products manufactured using ordinary portland cement react with salt and carbon dioxide absorbed from the soil and atmosphere in the use environment, causing contamination such as efflorescence. This is due to the reaction between calcium hydroxide, a cement hydration product, and carbon dioxide, producing and eluting calcium carbonate. This study was a preliminary study to compare and evaluate the reduction of efflorescence in concrete bricks and hollow concrete block products manufactured using carbon dioxide reaction hardening cement. The purpose was to evaluate the efflorescence occurrence in products using ordinary Portland cement.

• 한국폐기물자원순환학회지
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• 제35권8호
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• pp.721-730
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• 2018

We investigated the effects of heavy metals in cement in the last 3 years and the amount of waste in the cement manufacturing process. The result shows that the average $Cr^{6+}$ content in cement products is controlled at 10 mg/kg. Cu and Pb have lower detection tendency in white cement than in ordinary portland cement. In addition, heavy metals such as Cd show a certain level of detection regardless of the input wastes. Copper slag and phosphate gypsum are the main influencing factors on the heavy metals in cement products. In auxiliary fuels, plastics waste and wood waste are considered to affect heavy metals in cement products. Alternative raw materials are considered to be affected by the alternative raw materials managed as byproducts. In the case of supplementary fuels, auxiliary fuels managed as waste instead of auxiliary fuels managed as byproducts affect the heavy metals in cement. This study examined the input amount without considering the heavy metals in each waste. Therefore, the result may vary in different situations, and further research must be conducted to supplement the findings. However, if the heavy-metal contents in the waste are constant, it can be used as a reference material for the control of heavy metals in cement products.

• Advances in concrete construction
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• 제5권3호
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• pp.289-301
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• 2017

The synergistic interactions of supplementary cementitious materials (SCMs) with ordinary portland cement (OPC) in multi-blended systems could enhance the mechanical and durability properties of concrete and increase the amount of cement that can be replaced. In this study, the characteristics of the hydration products as well as paste microstructure of blended cement containing 20% coal fly ash, 10% rice hull ash and 10% sugar mill lime sludge in quaternary blended system was investigated. Portlandite content, hydration products, compressive strength, pore size distribution and microstructural architecture of hydrated blended cement pastes were examined. The quaternary blended cement paste showed lower compressive strength, reduced amount of Portlandite phases, and higher porosity compared to plain hardened cement paste. The interaction of SCMs with OPC influenced the hydration products, resulting to the formation of ettringite and monocarboaluminate phases. The blended cement paste also showed extensive calcium silicate hydrates and calcium aluminate silicate hydrates but unrefined compared to plain cement paste. In overall, the expected synergistic reaction was significantly hindered due to the low quality of supplementary cementitious materials used. Hence, pre-treatments of SCMs must be considered to enhance their reactivity as good quality SCMs can become limited in the future.

• 한국건축시공학회지
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• 제20권1호
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• pp.19-26
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• 2020

본 연구는 소성과정에서 다량의 이산화탄소를 배출하는 포틀랜드 시멘트를 대체할 수 있는 비소성 시멘트 개발을 목표로 하였다. 이를 위해 고로슬래그 미분말과 고칼슘 플라이애시, 소석회를 사용하였다. 또한 실험 결과를 통하여 배합비율에 따른 비소성 시멘트의 특성에 대해서 파악하고, 프리캐스트 콘크리트 제품으로의 적용 가능성을 파악하고자 하였다. 실험방법은 비소성 시멘트를 제작하여 증기양생을 실시하였고 재령 3, 7, 28일의 휨강도와 압축강도를 비교하여 각 배합비의 특성을 파악하였다. 재령 28일에는 흡수율 시험과 X선 회절 분석, 내부 미세구조를 관찰하였다. 시험 결과, NSC 모르타르는 Plain 모르타르에 비해 강도는 낮지만 재령 3일에서 다수의 배합이 품질 최소기준을 만족하였다. 흡수율 시험에서는 재령 28일 기준 모든 배합이 품질 최소기준을 만족하였다. 따라서 NSC 모르타르는 목표 PC제품 생산 원료로서 적용 가능성이 높다고 판단하였다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2019년도 추계 학술논문 발표대회
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• pp.176-177
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• 2019

As a result of the Rietveld analysis to determine the effect of carbon nanotubes on the hydration products of cement composites, the quantitative difference of hydration products according to the addition rate of carbon nanotubes was not significant. Ettringite, an early hydration product, was measured to be slightly higher than the planes with carbon nanotubes over all ages. Therefore, it seems that carbon nanotubes have no effect on the hydration production in cement paste.

• 시멘트 심포지엄
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• 1호
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• pp.41-49
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• 1973

It is generally characterised that the International Cement Industry Seminar sponsored by Rock Products us more pratical and technical information(data) on the cement processing and operation than other seminar or symposium. Especially at the 8th Internat

• International Journal of Concrete Structures and Materials
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• 제5권1호
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• pp.3-10
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• 2011

Theoretical models for prediction of the mechanical properties of cement mortar are developed based on the morphology and interactions of cement hydration products, capillary pores and microcracks. The models account for intermolecular interactions involving the nano-scale calcium silicate hydrate (C-S-H) constituents of hydration products, and consider the effects of capillary pores as well as the microcracks within the hydrated cement paste and at the interfacial transition zone (ITZ). Cement mortar was modeled as a three-phase material composed of hydrated cement paste, fine aggregates and ITZ. The Hashin's bound model was used to predict the elastic modulus of mortar as a three-phase composite. Theoretical evaluation of fracture toughness indicated that the frictional pullout of fine aggregates makes major contribution to the fracture energy of cement mortar. Linear fracture mechanics principles were used to model the tensile strength of mortar. The predictions of theoretical models compared reasonably with empirical values.

• 한국세라믹학회지
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• 제53권2호
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• pp.215-221
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• 2016

In this study, the utilization of the by-products of various industries was examined using raw materials of CSA high-functional cement such as coal bottom ash, red mud, phosphate gypsum, etc. Technology to improve energy efficiency and reduce $CO_2$ was developed as part of the manufacturing process; this technology included lower temperature sintering ($150{\sim}200^{\circ}C$) than is used in the OPC cement manufacturing process, replacement of CSA cement with the main raw material bauxite, and a determination of the optimum mix condition. In order to develop CSA cement, a manufacturing system was established in the Danyang plant of the HANIL Cement Co. Ltd., in Korea. About 4,200 tons of low purity expansion agent CSA cement (about 16%) and about 850 tons of the lime-based expansion agent dead burned lime (about 8%) were produced at a rate of 60 tons per hour at the HANIL Cement rotary kiln. To improve the OPC cement properties, samples of 10%, 13%, and 16% of CSA cement were mixed with the OPC cement and the compressive strength and length variation rate of the green cement were examined. When green cement was mixed with each ratio of CSA cement and OPC cement, the compressive strength was improved by about 30% and the expansibility of the green cement was also improved. When green cement was mixed with 16% of CSA cement, the compressive strength was excellent compared with that of OPC cement. Therefore, this study indicates the possibility of a practical use of low-cost CSA cement employing industrial wastes only.

• 콘크리트학회논문집
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• 제12권1호
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• pp.45-52
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• 2000

The quality of cement mortar products largely depends on various work conditions, specially on the grading and grade shape of aggregates. However, the effect of grading and grade shape on the quality is not considered by both KS codes and production processes, resulting in the increase of the possibility of quality degradation. The objective of this study was to investigate the effect of grading and grade shape on the strength and absorption characteristics of cement mortar products. Flexural and compressive strength increased with the increase of fineness modulus and W/C. The strength increase was measured larger with river sand than with crushed sand. Absorption tended to decrease with the increase of fineness modulus and W/C, but did not affected by the source of sand.