• Computers and Concrete
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• 제20권6호
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• pp.683-688
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• 2017

This paper presents the experimental investigations on the compressive strength and permeation properties of geopolymer concrete prepared with low calcium fly ash as the primary binder activated with different percentage of Alccofine. The durability aspect was investigated by performing permeable voids and water absorption tests since permeability directly influences the durability properties. The test results show that Alccofine significantly improves the compressive strength and reduces the water permeability thus enhances the durability of geopolymer concrete at ambient curing regime which encourages the use of geopolymer concrete at ambient curing condition thus promising its use in general construction also.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
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• pp.463-471
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• 2009

Cemented soils or concrete are usually cured under moisture conditions and their strength increases with curing time. An insufficient supply of water to cemented soils can contribute to hydration process during curing, which results in the variation of bonding strength of cemented soils. In this study, by the consideration of in situ water supply conditions, cemented sand with cement ratio less than 20% was prepared by air dry, wrapped, and underwater conditions. A series of unconfined compression tests were carried out to evaluate the effect of curing conditions on the strength of cemented soils. The strength of air dry curing specimen was higher than those of wrapped cured specimen when cement ratio was less than 10%, whereas it was lower when cement ratio was greater than 10%. Regardless of cement ratio, air dry cured specimens were stronger than underwater cured specimens. A strength increase ratio with cement ratio was calculated based on the strength of 4% cemented specimen. The strength increase ratio of air dry cured specimen was lowest and that of wrapped and underwater cured ones increased by square. Strength of air dry cured specimen dropped to maximum 30% after wetting when cement ratio was low. However, regardless of cement ratio, strength of wrapped specimens dropped to an average 10% after wetting.

• 한국건축시공학회지
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• 제19권5호
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• pp.421-429
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• 2019

양생조건이 GGBFS를 사용한 시멘트 콘크리트의 염화물이온 확산계수에 미치는 영향에 대한 연구를 진행하였다. 양생조건은 기중양생 ($20{\pm}2^{\circ}C$, RH $60{\pm}5%$)과 수중양생 ($20{\pm}2^{\circ}C$)으로 구분하였으며, GGBFS 치환율은 0%(대조군), 30%, 60%로 구분하여 3가지 배합의 콘크리트를 W/B 40%, 50%, 60%로 구분하여 제작하였다. 시험은 콘크리트 압축강도평가, 염화물이온확산계수 평가를 실시하였다. 콘크리트의 압축강도는 GGBFS 치환율이 증가할수록 수중양생 대비 기중양생 시험체의 압축강도의 발현율이 감소하였다. 염화물이온확산계수 측정결과 GGBFS치환율이 증가할수록 염화물이온 확산계수가 감소하였지만, 수중양생대비 기중양생 시험체의 콘크리트 염화물이온 확산계수는 증가하여 최대 111%까지 증가하는 것을 확인하였다.

• Elastomers and Composites
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• 제35권1호
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• pp.12-18
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• 2000

환경에 대한 관심과 정부의 규제 강화로 에폭시 코팅 산업 분야에서 발생되는 휘발성 유기 물질 방출을 최소화하기 위하여 꾸준히 기술 개발을 해오고 있다. 환경 친화적인 기술 개발의 일환으로 본 연구에서는 amine-epoxy adduct (AEA)형의 수용성 에폭시 경화제를 합성하였고, 그의 구조를 FT-IR, GPC, TG/DTA로 확인하였으며, 합성한 수용성 경화제를 이용하여 KER-828 그리고 KER-500과의 경화 물성을 비교 조사하였다. 실험 결과에 의하면 건조시간은 KER-828이 KER-500보다 빨랐으나 접착력 및 내 충격성은 KER-500이 우수하였다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2013년도 추계 학술논문 발표대회
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• pp.194-195
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• 2013

Recently, it is the tendency that the CO₂ gas generated in the manufacturing process is increased every year in case of the portland cement used in the most of constructions and civil engineering field. The method that uses the mineral admixtures as the cement substitute material in order to be more serious and as much as it occupies 7% of the global CO₂ gas outlet amount such as 1 ton produces the cement and it ejects the CO₂ gas of 0.4~1.0 ton, etc conclude this problem is examined. Therefore, PVA fiber was mixed into the inorganic binder recycling the blast furnace slag, which is the industrial byproduct with the purpose studying the Geo polymer which doesn't use the cement at all silica fume, red mud, and etc. In addition, the water curing temperature was differentiated and the strength characteristic of the curing body tried to be examined.

• 한국작물학회지
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• 제34권3호
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• pp.235-238
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• 1989

공시품종으로 Burley 21과 KB101을 수확한 후 건조상내에서 온도 처리와 습도 3처리를 조합하여 엽분별로 건조하였고, 수확시기에 엽중수분함량이 다른 잎을 우기에 비닐건조실 내에서 건조하여 부패엽발생정도를 조사하였던 바 그 결과는 다음과 같다. 1. 부패엽발생은 3$0^{\circ}C$에서 최대였고, $25^{\circ}C$에서 약간 감소하였으며, 35$^{\circ}C$에서는 현저히 감소하여 4$0^{\circ}C$에서는 100% RH 조건에서도 전혀 발생되지 않았다. 2. 습도 82%구에서는 부패엽이 10%정도로 아주 적었으나 이보다 고습조건일 수록 급속하게 증가되었다. 3. KB 101 육성계통이 Burley 21보다 부패엽 발생이 약간 적은 경향이었다. 4. 부패엽발생 부위는 주로 잎 엮은 부위에서 가장 많았고, 다음은 수확시 절단부위에서 않았다. 5. 엽분별로는 중엽에서 본엽에서 보다 부피엽발생율이 더 높았다. 6. 우기에 엽중수분함양이 높은 잎을 수확시는 부패엽발생이 않았고, 강우 4일 후의 수분상태 잎을 수확시는 거의 부패엽이 발생되지 않았다.

• 콘크리트학회논문집
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• 제29권2호
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• pp.141-148
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• 2017

본 연구는 PC부재의 공장생산에 있어서 여러 가지 증기양생 조건의 변수에 따른 고강도 콘크리트의 초기 압축강도 발현성상을 실험적으로 검증하고, 최적 양생조건을 확인하기 위한 것이다. 40 MPa 이상의 고강도 콘크리트 제조에는 보통 포틀랜드 시멘트를 사용하였으며, 콘크리트의 배합조건은 물-시멘트비 3종류(W/C 25%, 35% 및 45%)를 대상으로 하였다. 본 연구의 증기양생 변수로 (1) 전치양생 시간 3종류, (2) 최고 양생온도 3종류, (3) 최고온도 유지시간 3종류, (4) 승온 및 강온양생 온도 1종류 등을 대상으로 재령별 압축강도 시험을 실시하였다. 또한, 증기양생 및 표준양생에 따른 재령별 강도발현을 비교하였다. 실험결과, (1) 전치양생은 콘크리트의 초기 응결시간 이상, (2) 최고 양생온도는 $55^{\circ}C$ 이하, (3) 최고온도 유지시간은 6시간 이하로 하는 것이 증기양생 고강도 콘크리트의 강도발현에 적합한 양생조건으로 나타났다. 또한, 재령 28일에서 증기양생과 표준양생의 압축강도 발현성상의 역전현상이 발생하였다. 따라서 이러한 양생조건으로 PC부재의 생산성 및 현장관리를 위한 기초자료로 제시하고자 한다.

• 한국농공학회논문집
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• 제55권3호
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• pp.129-140
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• 2013

Bottom Ash is industrial by-product from a thermoelectric power plant. An immense quantities of bottom ash have increased each year, but most of them is reclaimed in ash landfill. In this study, in order to raise recycling rate of Bottom Ash, it is suggested to cure Bottom Ash (BA) mixtures mixed with cement, lime, Fly Ash (FA), and oyster shell (OS). Mixtures of 5~20 % mixing ratio had been cured for 1, 3, 7, 14, and 28 days using sealed curing and air-dry curing method. Unconfined compressive strength test was conducted to determine strength and deformation modulus ($E_{50}$) change for mixtures as mixing ratio and curing day, water contents of mixtures were measured after test. As a result, strength and $E_{50}$ were increased as mixing ratio and curing days, but values and tendencies of them appeared in different as kind of mixture, mixing ratio, curing method, and curing days. The results showed the addition of cement, lime, Fly Ash, and oyster soil in Bottom Ash could improved strength and $E_{50}$ and enlarge its field of being used.

• Advances in concrete construction
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• 제11권2호
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• pp.127-140
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• 2021

In this study, twenty-five geopolymer (GP) mixes were prepared by varying the alkaline solids to Metakaolin (MK) and sodium silicate to NaOH ratios from 0.1 to 0.5 and 0.2 to 1.0, respectively, thus giving a wide range of molar ratios of silica to alumina, sodium oxide to alumina and water to sodium oxide. The compressive strength of these GP mixes was determined for four curing schemes involving oven curing at 100℃ for 24 h and three ambient curing with the curing ages of 3, 14, and 28 days. The test results revealed that for the manufacture of GP binder for structural applications of strength up to 90 MPa, the molar ratio of silica to alumina should be greater than 2.3, sodium oxide to alumina should be between 0.6 to 1.2, and water to sodium oxide should not exceed 12. The compressive strength of ambient cured GP mortar gets stabilized at 28 days of ambient curing. Experimental findings were also corroborated by GP microstructure analysis. The embodied energy of MK-based GP mortars, especially of high strength, is significantly less than the cement mortar of equivalent strength.

• 대한치과기공학회지
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• 제9권1호
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• pp.67-72
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• 1987

This experimental study presented the study on the dimensional changes of occuring for the denture curing methods. The method is as follows: 1. The master die was made of wax. 2. The Silicon Rubber Mold was made into the same 80 casts. 3. The 80 Wax Plate were made of using the Base Plate Wax. 4. Flasking, Wax-wash, & Resin-packing were performed by the general procedures. 5. The curing method is performed through the four curing methods. (A, B, C, D). Table 2 shows the dimensional change after a day. Table 3 shows the dimensional change after soaking for 30 days in water of the degree of 36 Centigrade. As a result, the A curing method is the most denture curing.