• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표논문집(II)
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• pp.350-355
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• 1998

Preplaced aggregate concrete in the building fields has recently been used in the partial repair works for damaged reinforced concrete structures, and polymer-modified mortars have been employed as grouting mortars for the preplaced aggregate concrete. The objective of this study is to clear the properties of polymer-modified grouting mortars. Polymer-modified mortars using a polystyrene acrylic(St/Ac) emulsion as grouting mortars for preplaced aggregate concrete are prepared with various mix proportions, and tested for flexural and compressive strengths, adhesion in tension. The flexural strength of emulsion-modified grouting mortars does not give much variation with increasing fly ash replacement for cement and sand-binder ratio. With increasing polymer-binder ratio, the flexural strength and adhesion in tension of St/Ac emulsion-modified grouting mortars increases, become nearly constant or reaches a maximum at a polymer-binder ratio of 5%. From the test results, St/Ac emulsion-modified grouting mortar with a polymer-binder ratio of 5%, a fly ash replacement of 10% for cement and sand-binder ratio of 1.0 is recommended as a grouting mortar for preplaced aggregate concrete.

• Computers and Concrete
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• 제31권6호
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• pp.545-559
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• 2023

In this study, an experimental investigation was conducted to assess the influence of ground granulated blast furnace slag (GGBS) and silica fume (SF) on the fresh and hardened properties of grout specimens and preplaced aggregate concrete (PAC). Grout proportions were optimized statistically using a factorial design and were applied to 10 mm and 20 mm coarse aggregates to produce PAC. The results demonstrate that GGBS has a more significant effect on the compressive strength of grout compared to SF, with a small increase or decrease in the GGBS content having a greater influence on the compressive strength of grout than SF. The water to binder ratio had the most significant effect on the compressive strength of PAC, followed by the coarse aggregate size and sand to binder ratio. An empirical relationship to predict the compressive strength of PAC was proposed through an experimentally derived factorial design along with a statistical analysis of collectively obtained data and a deep literature review. The results predicted by the empirical relationship were in good agreement with those of PAC produced for verification.

• Advances in concrete construction
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• 제15권6호
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• pp.419-430
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• 2023

In this study, the effect of two types of aggregates (fly ash aggregate and shale aggregate) on the density, strength, and durability of preplaced lightweight aggregate concrete (PLWAC) was studied. The results showed that the 7 - 28 days strength of concrete prepared with fly ash aggregates (high water absorption rate) significantly increased, which could attribute to the long-term water release of fly ash aggregates by the refined pore structure. In contrast, the strength increase of concrete prepared with shale aggregates (low water absorption rate) is not apparent. Although PLWAC prepared with fly ash aggregates has a lower density and higher strength (56.8 MPa @ 1600 kg/m³), the chloride diffusion coefficient is relatively high, which could attribute to the diffusion paths established by connected porous aggregates and the negative over-curing effect. Compared to the control group, the partial replacement of fly ash aggregates (30%) with asphalt emulsion (20% solid content) coated aggregates can reduce the chloride diffusion coefficient of concrete by 53.6% while increasing the peak load obtained in a three-point bending test by 107.3%, fracture energy by 30.3% and characteristic length by 103.5%. The improvement in concrete performance could be attributed to the reduction in the water absorption rate of aggregates and increased energy absorption by polymer during crack propagation.

• Advances in concrete construction
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• 제11권5호
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• pp.409-417
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• 2021

The incorporation of non-biodegradable tyre waste in cement-based material has gained more interest towards sustainable construction these days. Crumb rubber (CR) from waste tyre is an alternative for sand replacement in low strength applications. Many researchers have studied CR cement-based materials produced by normal mixing (NM) method and reported a significant decrease in compressive strength due to CR. To compensate this strength loss, this research aims to study the innovative incorporation of CR in cement composite via the preplaced mixing (PM) method. In this investigation, cement composite was produced with NM and PM methods by replacing sand with 0%, 50%, and 100% CR by volume. The test results showed no significant difference in terms of densities of cement composite prepared with both mixing methods. However, cement composite prepared with PM method had lower strength reduction (about 10%) and lowered drying shrinkage (about 20%). In addition, the sound absorption coefficient and noise reduction coefficient of CR cement composite prepared by PM method were in similar range as those prepared with NM method. Overall, the results demonstrate that the PM method is promising, and the maximum replacement level of 50% is recommended for CR in the cement composite.

• 한국지반환경공학회 논문집
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• 제15권9호
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• pp.59-67
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• 2014

수중 구조물의 건설공사 수요 증가에 따라 구조물을 지반에 고정시키고 지지하기 위한 해양 기초 및 수중 그라우트재에 대한 관심이 높아지고 있고, 이에 대한 다양한 연구가 진행되고 있다. 수중에 시공되는 그라우트재는 물의 흐름에 의해 유실 교란되기 쉽고 양생 중에 재료분리 현상 등으로 인해 시공품질을 확보하기 어려워 설계 강도에 큰 영향을 미친다. 본 연구에서는 해상 모노파일 속채움과 같이 골재를 채운 후 그라우트재를 주입하는 프리플레이스트 공법에 대한 수중 불분리성 혼화제의 적용 효과를 파악하기 위해 골재 크기, 그라우트재의 종류, 물 시멘트비 및 혼화재 등 다양한 시험조건을 상정하여 블리딩 및 압축강도 등의 실내시험을 수행하였으며, 이에 따른 특성을 비교 평가하였다.

• 한국건설순환자원학회논문집
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• 제8권3호
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• pp.263-268
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• 2020

이 연구의 목적은 폐타이어 고무분말을 혼입한 폴리우레탄 복합재료와 굵은 골재를 사전채움하고 폴리우레탄을 주입한 폴리우레탄 복합재료의 감쇠성능을 평가하는 것이다. 이를 위하여 총 4 종류의 폴리우레탄 기반 복합재료를 제조하였고, 충격 가진 실험을 실시하였다. 실험을 통하여 시간 영역과 주파수 영역에서의 진동특성을 계측한 후 감쇠비를 계산하였다. 실험 결과, 고무분말을 혼입하여 폴리우레탄의 양이 각각 10.6%와 21.2% 줄어든 실험체들의 감쇠비는 순수한 폴리우레탄 실험체에 비하여 각각 8.4%와 4.6% 낮은 것으로 나타났다. 프리팩트 콘크리트 제조 방법과 유사한 방법으로 제조한 폴리우레탄 복합재료의 감쇠비는 순수 폴리우레탄에 비하여 22% 낮은 것으로 나타났지만 폴리우레탄 혼입량은 50% 감소하였으며, 강성은 25.7배 높은 것으로 나타났다.