• 콘크리트학회논문집
• /
• 제23권4호
• /
• pp.431-440
• /
• 2011

콘크리트 구조물은 화재에 노출시 고온에 의해 내부 구조가 변화하며 보유하고 있는 강도와 변형 성능이 저하되어 최종적으로 수명이 단축하게 된다. 그 성능 저하 수준은 도달된 온도, 고온에 노출된 시간, 콘크리트의 배합, 골재의 특성 및 콘크리트 자체의 특성 등에 의해 결정된다. 이 연구는 물시멘트비, 잔골재율 및 굵은 골재의 최대 크기등의 변수에 대한 초고강도 콘크리트의 열적 거동을 평가하기 위해 실시되었다. 상온 및 $500^{\circ}C$의 온도에 대하여 초음파 속도, 동탄성 계수, 정탄성 계수 및 압축강도 시험은 ${\varnothing}100{\times}200\;mm$ 원주형 콘크리트 시험체를 사용하여 실시되었다. 결과로서 $500^{\circ}C$의 온도에서 가열된 초고강도 콘크리트의 잔존 역학적 특성은 물결합재비, 잔골재율 및 굵은 골재 최대 치수의 변화에 영향을 받는 것으로 나타났다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
• /
• pp.407-410
• /
• 2005

This research investigates experimentally an effect on the properties of the combined high flowing concrete by mix design factors. The purpose of this study is to determine the optimum mix proportion of the combined high flowing concrete having good flowability, viscosity, no-segregation and design strength(40.0MPa). For this purpose, trial mixings used belite cement+lime stone powder(LSP) are tested by mix design factors including water-cement ratio($47.9\~54.0\%$), fine aggregate volume ratio($41\~45\%$) and coarse aggregate volume ratio($41\~45\%$). As test results of this study, the optimum mix proportion for the combined high flowing concrete is as followings. Water-cement ratio $51.0\%$, fine aggregate volume ratio $43{\pm}1\%$ and coarse aggregate volume ratio $0.30{\pm}0.05m^3/m^3$ and replacement ratio of LSP $42.7\%$.

• 한국농공학회:학술대회논문집
• /
• 한국농공학회 2003년도 학술발표논문집
• /
• pp.411-414
• /
• 2003

This study is performed to examine the physical and mechanical properties of recycled polymer concrete using recycled coarse aggregate and recycled fine aggregate. Tests for compressive strength, flexural strength and pulse velocity with replacement ratio of recycled coarse aggregate and recycled fine aggregate are performed. As a result, compressive strength, flexural strength and pulse velocity of polymer concrete containing recycled coarse aggregate are in the range of $826{\sim}849kgf/cm^2,\;192{\sim}200kgf/cm^2\;and\;3,932{\sim}4,000m/s$, respectively. Compressive strength, flexural strength and pulse velocity of polymer concrete containing crushed stone only are $805kgf/cm^2,\;197kgf/cm^2$ and 3,931 m/s, respectively. Accordingly, recycled aggregates is expected that can be utilizing as an aggregate of polymer concrete.

• 한국농공학회지
• /
• 제37권5호
• /
• pp.90-100
• /
• 1995

This study was performed to develop the lightweight concrete using synthetic lightweight aggregate and natural coarse aggregate. Mixing ratios were three types, the first type was mixed cement and synthetic lightweight fine aggregate (Type CP), the second type was mixed cement, synthetic lightweight fine aggregate and synthetic lightweight coarse aggregate (Type CPE), the third type was mixed cement, synthetic lightweight fine aggregate and natural coarse aggregate (Type CPN). The results of this study are summarized as follows ; 1. The W/C of each mixing ratio was increased with increase of the amount of cement used, and it was shown higher in order of Type CP, CPN, CPE. 2. The unit weight of Type CP, CPE and CPN was 1.473~1.647g/cm$^3$, 1.467~1.622g/cm$^3$ and 1.658~1 .838g/cm$^3$, respectively. And the absorption ratio was approximately 20%, which was higher than that of the normal cement concrete. 3. The compressive strength of Type CP was shown 178 ~249kg/cm2, Type CPE was shown 149~241kg/cm$^2$ and Type CPN was shown 196~297kg/cm$^2$, respectively. Each strength ratio was smaller than that of the normal cement concrete. 4. The pulse velocity of Type CP, CPE and CPN was 2, 688~3, 240m/sec, 2, 981~3, 324m/sec and 2, 989 ~ 3, 545m/sec, respectively. And it was increased with increase of strength and unit weight. 5. The length change ratio at 28 days was in the range of 0.057~0.077%, and earlier length change ratio was higher than that of the later.

• 자원리싸이클링
• /
• 제18권3호
• /
• pp.20-26
• /
• 2009

본 연구는 순환잔골재를 사용한 콘크리트의 굳지 않은 콘크리트 특성을 파악하고 순환골재 콘크리트의 품질관리 방안을 제시하고자 하였다. 이를 위하여 순환굵은골재 및 순환잔골재의 치환율을 조합하여 설계압축강도 30MPa의 콘크리트를 제작하였으며, 공기량 및 슬럼프를 측정하였다. 측정된 공기량 및 슬럼프 경시변화를 통하여 순환잔골재의 재료적 특성이 콘크리트의 물성에 미치는 영향을 파악하였으며, 골재의 흡수율 차에 따른 품질성능 저하를 고려할 수 있도록 현장 도착 슬럼프를 기준으로 전체 배합수를 일정하게 유지하는 품질관리 방안을 제시하도록 하였다. 본 실험에서는 골재 종류(천연, 순환)에 따른 표면수 보정을 통해 1시간 후 현장도착 슬럼프가 일정하게 유지될 수 있도록 콘크리트를 배합하였다. 순환골재의 사용에 따른 압축강도의 저하는 나타나지 않았다. 또한 표면수 보정을 통한 전체 배합수의 관리를 통하여 순환골재 콘크리트의 품질관리가 가능할 것으로 판단된다.

• KCI Concrete Journal
• /
• 제11권3호
• /
• pp.19-28
• /
• 1999

This study treated self-compacting high Performance concrete as two Phase materials of Paste and aggregates and examined the effect of powder and aggregates on self-compacting high performance, since fluidity and segregation resistance of fresh concrete are changed mainly by paste. To improve the fluidity and self-compactibility of concrete, optimum powder ratio of self-compacting high performance concrete using fly ash and blast-furnace slag as powders were calculated. This study was also designed to provide basic materials for suitable design of mix proportion by evaluating fluidity and compactibility by various volume ratios of fine aggregates, paste, and aggregates. As a result, the more fly ash was replaced, the more confined water ratio was reduced because of higher fluidity. The smallest confined water ratio was determined when 15% blast-furnace slag was replaced. The lowest confined water ratio was acquired when 20% fly ash and 15% blast-furnace slag were replaced together. The optimum fine aggregates ratio with the best compactibility was the fine aggregate ratio with the lowest percentage of void in mixing coarse aggregate and fine aggregate In mixing the high performance concrete. Self-compacting high performance concrete with desirable compactibility required more than minimum of unit volume weight. If the unit volume weight used was less than the minimum, concrete had seriously reduced compactibility.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2015년도 춘계 학술논문 발표대회
• /
• pp.67-68
• /
• 2015

Recently, usage of ultra-high strengh concrete(UHSC) have been increased. Concrete has been recognized as a material which is resistant to high temperatures, but chemicophysical property of concrete is changed by the high temperature. So, mechanical properties of concrete may be reduced. Therefore, this study evaluated effect of the coarse Aggregate volume by high temperature mechanical properties of UHSC. Residual mechanical properties are evaluated under fine aggregate ratio 40,60% and 500℃ temperature on UHSC of W/B 15, 20%. As result, residual mechanical properties of UHSC are high by lower coarse aggregate volume.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
• /
• pp.388-391
• /
• 2004

This research investigates how the fineness modulus of fine aggregates and the grain shape of coarse aggregates affects flow characteristics, packing characteristics and compressive strength characteristic. The experimental results, show that increase of the fine aggregate's fineness modulus improved concrete flow, but filling ability was high at over KS regulation extent due to segregation phenomena. It is considered that the improvement of 0.1 spherical rate was effective to concrete fluidity elevation by reducing about $6\%$ of fine aggregate ratio displays which the smallest gap rate of aggregate. Compressive strength was increased to about 0.6MPa everytime F.M. 0.1 of fine aggregate fineness is increased. However, it was decreased to about 9MPa at F.M. 3.5 compared to F.M. 3.0.

• 콘크리트학회논문집
• /
• 제17권5호
• /
• pp.785-792
• /
• 2005

본 연구는 굵은골재의 입형불량과 잔골재의 조립률 저하가 초유동콘크리트의 특성에 미치는 영향을 검토한 것이다. 이론 위해 잔골재 조립률을 2.0, 2.5, 3.0, 3.5로 변화시키고 굵은골재는 입형개선전$\cdot$후 골재를 사용하여 초유동콘크리트의 유동검 및 충전성능을 검토하였다. 또한 골재입자의 분산거리를 상대비교 함으로써 잔골재의 조립률 및 굵은골재의 입형이 골재입자의 분산거리에 미치는 영향을 검토하였다. 실험 결과 굵은골재와 잔골재 혼합시의 최소공극률은 골재 입형개선 유무에 관계없이 잔골재 조립률 3.0, 2.5, 2.0, 3.5 순으로 나타나 조립률 KS 규정 값 $2.3\~3.1$보다 작거나 클 경우 공극률을 증가시키는 것으로 나타났으며, 굵은골재의 입형은 구형율 0.69의 원반상에서 구형율 0.78의 구상으로 개선할 경우 최소공극률을 나타내는 잔골재율을 $47\%$에서 $41\%$로 $6\%$ 감소시키는 것으로 나타났다. 잔골재 조립률에 따른 28일 압축강도 특성은 조립률 2.0에서 2.5, 3.0으로 증가할수록 약 3MPa씩 증가하였으나, 조립률 3.5에서는 3.0에 비해 약 9MPa 정도 감소하였다. 또한 굵은골재의 입형개선과 잔골재 조립률의 증가는 유동성, 충전성 및 V로드 상대유하시간을 향상시키는 것으로 나타났으며, 잔골재 조립률은 KS 규정 값 $2.3\~3.1$을 만족하는 범위내에서 높은 값을 사용하는 것이 페이스트 용적비를 증가시키는 것으로 나타났다.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2015년도 춘계 학술논문 발표대회
• /
• pp.61-62
• /
• 2015

This study has analyzed the engineering characteristics of resource-cycling mortar according to the variation of fine aggregate type using illite with high development potentials by setting the goal as developing eco-friendly construction materials. As a result, while flow has increased if recycled fine aggregate and waste refractory are used separately or mixing them adequately in case of flow and compressive strength, the flow had somewhat declined followed by illite replacement. However, the possibility of such usage is determined to be adequate if used by mixing illite, recycled fine aggregate and waste refractory properly due to the dry shrinkage effect.