• 한국세라믹학회지
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• 제37권7호
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• pp.681-685
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• 2000

The influence of ZnCl2 in portland cement hydration was studied. The hydration reaction was progressed with ZnCl2 solution to observe the adiabatic hydration exothermic and hydration products. To compare with cement hydration, Ca(OH)2 solution reacted with ZnCl2 was carried out. The addition of ZnCl2 solution to the portland cement was retarded hydration quantitatively. Because ZnO which was produced in certain pH adsorbed with unhydrated cement made retarded the hydration reaction.

• 콘크리트학회논문집
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• 제16권4호
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• pp.557-564
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• 2004

This paper introduces a study carried out to investigate sodium sulfate attack caused by various reactive products. Experiments were performed on mortar and paste specimens made with ordinary Portland cement (OPC) conforming to KS L 5201 Type I. The water-cement ratios were varied from 0.35 to 0.55. It was found from the laboratory study that the water-cement ratio may be a key to control the deterioration of OPC matrix during sodium sulfate attack. Furthermore, X-ray diffraction (XRD) confirmed that ettringite, gypsum and thaumasite were the main products formed by sodium sulfate attack. These findings were well supported by thermal analysis through differential scanning calorimetry (DSC), and confirmed the long-term understanding that deterioration mechanism by sodium sulfate attack is a complicated process. Most importantly, deterioration due to sodium sulfate attack is characterized as the drastic reduction in compressive strength as well as the expansion (especially in cement matrix with a higher water-cement ratio).

• 한국환경보건학회지
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• 제34권1호
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• pp.108-115
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• 2008

This study was performed to investigate the current status, in Korea, of the production of asbestos containing products (ACPs) such as asbestos cement products, asbestos friction materials, asbestos joint sheets, asbestos textile products, and other asbestos-containing products from May 2 to July 30, 2007. The information on ACPs was obtained through written questionnaires from 16 of the 27 companies that produce ACPs in Korea. The production amounts of asbestos containing gaskets were 70 tons in 2004, 90 tons in 2005, and 55 tons in 2006 in 4 companies and that of asbestos friction materials were 435.5 tons in 2004, 540.4 tons in 2005, and 454.3s ton in 2006 in 10 companies. The type and number of ACPs were:- 19 asbestos cement products, produced by 2 companies; 47 asbestos friction materials produced by 18 companies; 12 asbestos joint sheets productes by 4 companies; 18 asbestos textile products from 3 companies, and 6 other asbestos products from 5 companies. The database of ACPs was constructed to include the products name, identification number, name of company, production year, composition, asbestos content (%), usage, specification, and a picture. The database will be used to efficiently identify ACPs and to avoid asbestos exposure in workers and the general population.

• 한국건축시공학회지
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• 제19권4호
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• pp.323-330
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• 2019

시멘트 산업은 온실가스 감축을 위한 주요 산업분야로 고려되고 있으며, 콘크리트에 시멘트를 대체할 수 있는 재료의 사용량을 증가시키는 것은 이산화탄소 감축을 위해 효과적인 방법으로 알려져 있다. 따라서 시멘트의 일부를 대체하여 사용할 수 있는 산업부산물을 다량으로 활용하기 위한 연구가 진행되고 있다. 그러나 산업부산물의 혼합량을 증가시키지 못하는 큰 이유로 초기강도 저하와 응결지연에 대한 문제점이 있다. 따라서 이 연구에서는 보통 시멘트를 사용한 경우와 고분말도 시멘트를 사용한 경우에 대해 플라이애시의 사용량에 차이를 두고 물리적 특성을 검토하여, 시멘트의 사용량을 줄이고 산업부산물을 다량으로 사용하기 위한 방안으로서, 고분말도 시멘트를 활용한 결과에 대한 기초 자료를 제시하였다.

• Geomechanics and Engineering
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• 제13권3호
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• pp.459-474
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• 2017

To investigate the mechanical properties of Expanded Polystyrene (EPS) Beads Stabilized Lightweight Soil (EBSLS), Laboratory studies were conducted. Totally 20 sets of specimens according to the complete test design were prepared and tested with unconfined compressive test and consolidated drained triaxial test. Results showed that dry density of EBSLS ($0.67-1.62g/cm^3$) decreases dramatically with the increase of EPS beads volumetric content, while increase slightly with the increase of cement content. Unconfined compressive strength (10-2580 kPa) increases dramatically in parabolic relationship with the increase of cement content, while decreases with the increase of EPS beads volumetric content in hyperbolic relationship. Cohesion (31.1-257.5 kPa) increases with the increase of cement content because it is mainly caused by the bonding function of hydration products of cement. The more EPS beads volumetric content is, the less dramatically the increase is, which is a result of the cohesion between hydration products of cement and EPS beads is less than that between hydration products of cement and sand particles. Friction angle ($14.92-47.42^{\circ}$) decreases with the increase of EPS beads volumetric content, which is caused by the smoother surfaces of EPS beads than sand grains. The stress strain curves of EBSLS tend to be more softening with the increase of EPS beads content or the decrease of cement content. The shear contraction of EBSLS increases with the increase of $c_e$ or the decrease of $c_c$. The results provided quantitative relationships between physico-mechanical properties of EBSLS and material proportion, and design process for engineering application of EBSLS.

• 한국건설순환자원학회논문집
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• 제12권3호
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• pp.306-313
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• 2024

본 연구는 국내 시멘트 산업의 폐합성수지 활용 현황과 대체연료 사용량 증가에 따른 시멘트 내 염화물 함량에 대해 조사하였으며, 국내외 시멘트 및 콘크리트 내 염화물 기준 조사를 통해 KS제도 개선 필요성에 대해 고찰하였다. 2016~2023년에 조사된 각사별 연평균 염화물 함량 중 최대값은 485 ppm이었으며, 폐합성수지 사용량 증가 시 1,033 ppm까지 증가할 것으로 계산되었다. 국내 콘크리트 염화물 관리 기준은 총량제로서 0.3 kg/m³ 로 제한하고 있지만, 계산된 시멘트 염화물량(1,033 ppm)을 기준으로 하였을때 단위시멘트량이 290 kg/m³ 이상이 되는 경우 현행 KS 염화물 기준을 만족하기 어려운 것으로 나타났다. 해외 다수의 국가에서는 시멘트 투입량에 따라 콘크리트 염화물량을 제한하는 종량제를 채택하고 있는 상황에서, 한국 또한 시멘트 산업의 탄소중립 달성을 위해서 연구수행을 통한 합리적 염화물 기준도출과 이해관계자 공감대 형성을 통해 종량제 도입 추진이 검토되어야 할 것으로 생각된다.

• 한국건축시공학회지
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• 제6권3호
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• pp.75-82
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• 2006

This study investigates the influence of various blending factors on cement paste fluidity and find out the most effective evaluation method of cement paste flow, comparing flow test apparatuses such as ring flow(R-F), flow cone(F-C) and mini slump(M-S). A viscometer also measures the rheology coefficients to secure faithful numerical data. Firstly, series I examines cement paste, affected by several cement products and mineral admixture types in the range of W/B 40%, ordinary fluidity, and W/B 30%, high fluidity. In this series, the three types of cement product depended on companies, are randomly used and the mineral admixture, such as fly ash, blast furnace slag and silica fume, are incorporated in the cement paste, in response to the ratio of 10, 20, to 30%, respectively. In addition, series II studies various chemical admixture types, affecting the cement paste. This series is carried out with manufacturing companies and component types in the range of W/C 30%, high fluidity. For the manufacturing companies, randomly four products are used and for the component types, polycaboxylate, melamine, naphthalene and lignosulfonate type are chosen. Test results showed that in the fluidity test of cement paste considering various types of blending factors, R-F exhibited similar tendency with F-C and M-S. In the analysis of consistency curves measured by viscometer, the fluidity evaluation method using flow test apparatuses was significantly effective, except for the some of the low fluidity specimens. In conclusion of this study, R-F was the most convenient, faithful and effective fluidity evaluation method of cement paste.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1993년도 가을 학술발표회 논문집
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• pp.144-149
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• 1993

The results of an experimental study on the manufacture and the mechanical properties of carbon fiber reinforced silica fume.cement composites and light weight fly ash.cement composites are presented in this paper. The CF reinforced silica fume.cement composites using silica fume early strength cement were prepared with Pan-derived or Pitch-derived CF, and Lt. Wt, fly ash.cement composites using fly ash, early strength cement, perlite and a small amount of foaming agent. As the test results show, the flexural strength, toughness and ductility of CF reinforced silica fume .cement composites were remarkably increased by fiber contents. Also, the manufacturing process technology of Lt. Wt. fly ash.cement composites was developed and its optimum mix proportions were proposed. And the compressive and flexural strength of the fly ash.cement composites by hot water cured were improved even more than by moist cured, but are decreased by increasing fly ash replaced ratio for cement.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 봄 학술논문 발표대회
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• pp.179-180
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• 2020

CO2 emissions are caused by cement manufacturing process. To solve this problem construction industry are using industrial by-products to replace cement. In this study, three different industrial by products were used and mixed with hybrid fibers to enhance bond strength. As the result, Regardless of the mixing rate of silica fume, the compressive strength of the ternary non cent mortar was higher than that of OPC and binary. And mixed hybrid fibers cured by room temperature compressive strength were 23% higher than those without hybrid fibers.

• Corrosion Science and Technology
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• 제8권3호
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• pp.110-115
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• 2009

At the onset of corrosion of steel in concrete, hydrogen ions usually evolve in the process of electrochemical reaction, thereby decreasing the pH of the pore solution, which can be buffered by cement hydration products, as being representatively illustrated by calcium hydroxide. Hence, a fall in the pH is dependent on properties of cement hydration (i.e. hydration products and degree of hydration). The present study tested acid neutralization capacity (ANC) of cementitious binders of OPC(Ordinary Portland Cement), 30% PFA(Pulverized Fuel Ash), 60% GGBS(Ground Granulated Blast Furnace Slag), 10% SF(Silica Fume) to quantify the resistance of cement matrix to a pH fall. Cement pastes were cast at 0.4 of a free W/C ratio with 1.5% chlorides by weight of binder in cast. Powder samples obtained crushed and ground specimen after 200 days of curing were diluted in still water combined with different levels of 1M nitric acid solution, ranging from 0.5 to 20 mol/kg. Then, the pH of diluted solution was monitored until any further change in the pH did not take place. It was seen that the pH of the diluted solution gradually decreased as the molar amount of nitric acid increased. At some particular values of the pH, however, a decrease in the pH was marginal, which can be expressed in the peak resistances to a pH fall in the ANC curve. The peaks occurred at the variations in the pH, depending on binder type, but commonly at about 12.5 in the pH, indicate a resistance of precipitated calcium hydroxide. The measurement of water soluble chloride at the end of test showed that the amount of free chloride was significantly increased at the pH corresponding to the peaks in the ANC curve, which may reflect the adsorption of hydration products to chlorides.