• International Journal of Concrete Structures and Materials
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• 제5권2호
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• pp.125-131
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• 2011

Five all-lightweight alkali-activated (AA) slag concrete mixes were tested according to the variation of water content to examine the significance and limitation on the development of cementless structural concrete using lightweight aggregates. The compressive strength development rate and shrinkage strain measured from the concrete specimens were compared with empirical models proposed by ACI 209 and EC 2 for portland cement normal weight concrete. Splitting tensile strength, and moduli of elasticity and rupture were recorded and compared with design equations specified in ACI 318-08 or EC 2, and a database compiled from the present study for ordinary portland cement (OPC) lightweight concrete, wherever possible. Test results showed that the slump loss of lightweight AA slag concrete decreased with the increase of water content. In addition, the compressive strength development and different mechanical properties of lightweight AA slag concrete were comparable with those of OPC lightweight concrete and conservative comparing with predictions obtained from code provisions. Therefore, it can be proposed that the lightweight AA slag concrete is practically applicable as an environmental-friendly structural concrete.

• 한국해양공학회지
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• 제17권4호
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• pp.16-22
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• 2003

The mechanical characteristics of newly recycled aggregate concrete on the basis of the proposed mix design model have been studied to develop the precast artificial fishing reefs. In the first task, the experimental test for the recycled aggregates taken from Jeju Island has been carried out to verify the material properties in terms of specific gravity, percentage of solids, absorption and abrasion of coarse aggregates. In the second task, the experimental parameters of newly recycled aggregate concrete are investigated to meet with the requirements of guidelines with respect to slump, unit weight, pH, ultrasonic velocity, void ratio, and compressive strength which are made of sea-shore sand ad slag cement. The natural aggregate and polypropylene fiber are added to newly recycled aggregate concrete to improve the compressive strength and quality. The optimal mix proportions for compressive strength are W/C=30％, S/a=15％, NA/G=50％ in porous concrete case, W/C=40％, S/a=45％ in plain concrete case, and W/C=40％, S/a-45％, PF=1.0kg/㎥ in fiber reinforced concrete case.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2010년도 춘계 학술대회 제22권1호
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• pp.345-346
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• 2010

수중불분리 콘크리트의 품질은 혼화제의 성능 및 배합비와 같은 변수들에 영향을 받으며, 이들 중 혼화제의 성능은 수중불분리 콘크리트의 품질에 많은 영향을 주고 있다. 따라서, 본 연구에서는 수중불분리성 혼화제를 사용한 콘크리트의 슬럼프 플로우, 응결시간, 압축강도 및 수중분리도를 측정하여 수중불분리성 혼화제의 성능을 평가하였다. 그 결과, 수중불분리성 혼화제를 사용한 콘크리트는 플레인 콘크리트보다 유동성, 압축강도 및 수중불분리도와 같은 콘크리트의 품질이 개선되는 것으로 나타났다.

• 콘크리트학회논문집
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• 제12권5호
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• pp.111-120
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• 2000

In case of constructing concrete structure under water, generally concrete mixed with antiwashout admixture, high range water reducer, or AE-water reducing agent etc has been manufactured to ensure the quality of antiwashout underwater concrete because of being difficulty in ascertaining construction situation by the naked eye. The properties of high quality antiwashout underwater concrete that were aimed at affluent fluidity, workability and the compressive strength of 450 kgf/$\textrm{cm}^2$ at 28 ages using two types of blended cements are following as;(1) Setting time of antiwashout underwater concretes using blended cements was more greatly delayed than that of control concrete, however, was satisfied with criteria value of "Quality standard specification of antiwashout admixture for concrete".(2) As a test results of slump flow, efflux time and box elevation of head, it was found that workability of high quality antiwashout underwater concrete was improved. (3) Heat evolution amount of OPC was 1.5 times as high as that of two types of bended cements in 72 hours. (4) Suspended solids of antiwashout underwater concrete using blended cements was more than that of control concrete, also compressive strength of high quality antiwashout underwater concrete was very low in early age, but was better than that of control concrete as to increasing ages.

• 한국건축시공학회지
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• 제4권2호
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• pp.97-103
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• 2004

In this study, the experiment was carried out to investigate and analyze the influence of coarse aggregate's mix ratio and maximum size on the properties of concrete. The main experimental variables were water/cement ratio 45% and 65%, coarse aggregate/fine aggregate ratio 90%, 130% and 170%, maximum size of coarse aggregate 15mm, 25mm and 40mm. According to the test results, the principal conclusions are summarized as follows. 1) The slump and flow of fresh concrete were found to be higher in the order of G/S ratio 170%, 130%, 90%, also in the order of maximum size 40mm, 25mm, 15mm. 2) The compressive strength of hardened concrete were found to be higher in the order of G/S ratio 170%, 130%, 90%, also in the order of maximum size 15mm, 25mm, 40mm.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 춘계 학술논문 발표대회
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• pp.87-91
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• 2008

The study examined fire resistance of concrete followed by change of mixed rate in PP and NY composite fiber and the results were as follows. In the event of fluidity in concrete not set, plane satisfied 600±100, its target slump flow, and fluidity was reduced as organic fiber's mixed rate was increased. Air amount satisfied 3.0±1.0, its target air amount, and didn't have distinct differences in reduction and increase according to organic fiber's kind and change of its mixed rate. However, it had a tendency that fluidity was reduced as the mixed rate was increased. In characteristics of hardening concrete, the 28th day compressive strength followed by organic fiber's kind and change of its mixed rate didn't have a lot of differences and satisfied high strength scope as about 70MPa. In spalling characteristics after fire resistance test, spalling was happened in non-mixture, plane combination, and P1N0. In other combinations, spalling resistance was happened. The relic compressive strength rate was 56%, the best condition, in P3N1(PP0.03%, NY0.01% compositeness) mixing PP fiber with NY fiber at once.

• 공업화학
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• 제8권6호
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• pp.979-984
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• 1997

폴리머 혼화제로서 styrene-butadiene rubber(SBR)라텍스, ethylene-vinyl acetate(EVA)에멀젼 및 polyacrylic ester(PAE)에멀젼을 사용하여 동일한 스럼프에서 폴리머-시멘트비를 변화시켜 공시체를 제조하여, 압축과 휨강도시험, 흡수시험, 세공분포측정 및 미세구조 관찰 등을 실시하였다. 그 결과 폴리머-시멘트비의 증가와 더불어 압축과 휨강도 모두 향상되었고, 동해에 큰 영향을 주는 모세관 공극범위의 세공량은 감소되었으며, 폴리머 시멘트비 15wt% 이상에서 연속적인 폴리머필름이 형성되었다.

• 한국구조물진단유지관리공학회 논문집
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• 제18권4호
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• pp.84-91
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• 2014

본 연구에서는 콘크리트 구조물의 강도 향상을 위하여 혼입하고 있는 메타카올린의 내구성능 향상 효과를 규명하기 위하여 염화물이온 확산계수 및 단열온도상승량을 측정하였다. 그 결과, 메타카올린의 혼입으로 인하여 염화물이온 확산계수가 작아짐이 확인되었으며 플라이 애쉬의 첨가를 통하여 유동성의 저하를 억제할 수 있었다. 따라서 염분침투저항성을 확보하면서 물결합재비를 크게 하는 것이 가능하므로 메타카올린의 혼입으로 발생되는 단열온도상승량을 억제할 수 있어 콘크리트의 내구성능이 향상될 수 있음을 확인하였다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2005년도 추계 학술논문 발표대회
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• pp.57-61
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• 2005

Cement paste is originally the basic material and crucial factor consisting concrete. This study investigates the relationship between flow apparatuses, which are ring flow(R-F), flow cone(F-C) and mini slump(M-S), in order to estimate the fluidity of cement Paste. For quantitatively evaluating the measured data this study also investigated the calibration of the rheology consistent, such as yield value and plastic viscosity, of cement paste using viscometer For this purpose the present work discussed the influence of 3 type of ordinary portland cement with different companies, affecting the fluidity of cement paste. and it also demonstrated the influence of the various kinds of mineral admixtures, such as fly ash(FA), blast furnace slag(BS) and silica fume(SF) and that of incorporating ratio. The author concluded that using R-F apparatus is the most effective flow test method of cement paste and it is exactly proportional to other apparatus' rheological properties.

• 콘크리트학회논문집
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• 제11권4호
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• pp.31-41
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• 1999

Blended Low Heat type cement is ground granulated blast furnace slag and fly ash mixed ternary with ordinary portland cement. From the viewpoint of X-ray patterns of domestic LHC, the main components of cement such as $C_2$S, $C_3$A, $C_3$S are considerably reduced. Therefore the heat evolution of LHC paste is 42cal/g lower than of OPC paste. At early age, the compressive strength development of LHC concrete is delayed, but the slump loss ratio of fresh concrete is reduced more than 20% with elapsed time. The penetrability of LHC is lower than that of OPC by 1/7.8 with the penetrability of chloride ion into the concrete until the age of 120 days. And the PD Index value of LHC is 0.44$\times$10-6 $\textrm{cm}^2$/s, which indicates only 39.3% of OPC. From the Mercury Intrusion Porosimetry test of cement past, we know that the pore size of LHC is more dense than that of OPC by production of C-S-H.