CSA 팽창재를 혼입한 강섬유 보강 콘크리트의 역학적 성능 및 균열 저항성능 평가

최세진,박기태,권성준 한국구조물진단유지관리공학회 2014 한국구조물진단유지관리공학회 논문집 Vol.18 No.1

콘크리트의 취성파괴를 방지하기 위해 강섬유 보강재는 효과적인 복합재료이다. 그러나 시멘트 사용량이 많아지면 건조수축이 증가하고이로 인해, 강섬유 보강재의 연성증가 효과가 제한될 수 있다. 팽창재를 사용한 콘크리트 내부의 강섬유 보강재는 화학적 프리스트레싱 효과가 발생하여 강섬유 보강효과를 증가시킬 수 있다. 본 연구에서는 CSA 팽창재와 강섬유 보강재를 혼입하여 콘크리트의 역학적인 특성을분석하였다. 체적비 1~2%의 강섬유 보강재와 시멘트 중량의 10%의 CSA 팽창재를 혼입하였으며, 다양한 역학적 특성과 휨거동을 분석하였다. 강섬유 보강재를 혼입한 CSA 콘크리트는 인장강도와 초기균열강도의 증가를 나타냈으며, 균열후의 파괴에너지 증가와 같은 연성거동을 뚜렷하게 나타내었다. 적절한 팽창재 사용과 최적의 강섬유 보강재의 혼입률이 도출된다면 이들의 상호작용은 콘크리트의 취성을 더욱 효과적으로 제어할 수 있다. In order to prevent brittle failure of concrete, steel fiber reinforcement is effective composite material. However ductility of steel fiber reinforced concrete may be limited due to shrinkage caused by large content of cement binder. Chemical prestressing for steelfiber reinforcement in cement matrix can be induced through expansive admixture and this can increase reinforcing effect of steel fiber. In this study, mechanical performances in concrete with CSA (Calcium sulfoaluminate) expansive admixture and steel fiberreinforcement are evaluated. For this work, steel fiber reinforcement of 1 and 2% of volume ratio and CSA expansive admixture of 10% weight ratio of cement are added in concrete. Mechanical and fracture properties are evaluated in concrete with steel fiber reinforcement and CSA expansive admixture. CSA concrete with steel fiber reinforcement shows increase in tensile strength, initialcracking load, and ductility performance like enlarged fracture energy after cracking. With appropriate using expansive admixture and optimum ratio of steel fiber reinforcement, their interactive action can effectively improve brittle behavior in concrete.

압축강도와 팽창재 대체에 따른 폴리에틸렌 합성섬유로 보강된 변형 경화형 시멘트 복합체의 역학적 특성

송영재,윤현도,민병성,육향 혜철 한국구조물진단유지관리공학회 2012 한국구조물진단유지관리공학회 논문집 Vol.16 No.2

변형경화형 시멘트 복합체(SHCC)는 직접인장 상황에서 FRCCs에 비해 우수한 변형경화 특성을 갖는 재료이다. 하지만 SHCC는 일반적인 콘크리트에 비해서 시멘트비율이 높은 부배합 이며, 이에 따라서 자기수축이 큰 특성을 갖는 재료이다. 따라서 시멘트 복합체 내에 팽창재를 대체함으로써 수축저감을 통한 성능향상을 기대하였다. 이 연구에서는 각 강도별 SHCC의 배합에 팽창재를 대체함에 따른 역학적특성을 평가하고자 하였다. 시험결과 설계기준 압축강도 70MPa 배합이 압축, 인장, 휨, 시험에서 우수한 역학적 특성을 나타내었으며, 균열 특성에서는 팽창재를 대체한 SHCC가 균열분산 및 연성에서 우수한 특성을 나타내었다. In order to improve the dimensional stability and mechanical performance of cement-based composites, the effect of an expansive admixture based on calcium sulphoaluminate (CSA) on the shrinkage and mechanical properties of strain-hardening cement-based composite (SHCC), which exhibits multiple cracks and pseudo strain-hardening behavior in the direct tension, is investigated. Polyethylene fibers reinforced SHCC mixtures with three levels (30, 70, and 100MPa) of compressive strength were compared through free shrinkage, compressive strength, flexural strength, and direct tensile strength measurements. The SHCC mixtures were cast with and without replacing 10% of Portland cement content with CSA admixture. According to test results, CSA admixture is effective in reducing shrinkage of SHCC material. SHCC mixture with CSA admixture exhibited a little higher strength than companion mixture without CSA admixture.

CSA계 팽창재를 사용한 무수축 콘크리트의 반복하중하에서의 균열발생 특성평가

송태협(Song, Tae-Hyeob),박지선(Park, Ji-Sun) 대한건축학회 2016 대한건축학회 학술발표대회 논문집 Vol.36 No.2

CSA계 팽창재 및 무기질 혼화재를 이용한 고성능 콘크리트의 특성에 관한 연구

한천구,반호용,전병채,홍상희,Han, Cheon-Goo,Bahn, Ho-Yong,Jun, Byung-Chea,Hong, Sang-Hee 한국콘크리트학회 1999 콘크리트학회지 Vol.11 No.1

최근 개발되고 있는 고유동, 고강도 및 고내구성을 발휘하는 고성능 콘크리트는 현대개념에 부응하는 양호한 품질을 발휘하는 이면에 물결합재비가 작고 단위결합재량이 많은 배합일수록 비경제적 및 건주수축과 자기수축이 대단히 커진다는 것이 보고되고 있고, 경우에 따라서는 자기수축만으로도 균열이 발생하는 일이 지적되고 있다. 따라서 본 연구에서는 무기질 혼화재인 플라이애쉬, 실리카 흄 및 플라이애쉬:실리카 흄 치환비 변화로써 워커빌리티등 각종품질의 향상과 구조물에 발생되는 건조수축 및 자기수출 균열을 CSA계 팽창재로 방지하므로써, 경제적이고 저균열${\cdot}$고품질인 고성능 콘크리트를 개발하고자 하였다. 연구결과 팽창재 혼입율 5%, F.A:S.F 15:5로 치환하면 유동성 및 강도특성이 양호하면서 건조수축 및 자기수축 보상효과가 있는 양호한 고성능 콘크리트가 성취될 수 있음을 알 수 있었다. Recently, high performance concrete developed has a good quality at fresh and hardened state, but high binder contents results in spending much money on manufacturing and many cracks by drying and autogenous shrinkage, Therefore, in this paper, not only prevention of cracks caused by drying and autogenous shrinkage, but improvement of quality and accomplishment of economy by applying F.A(fly ash), S.F(silica fume) and CSA(calcium sulfa aluminate) expansive additives as an inorganic admixtures in W/B 35% are discussed. According to the experimental results, when 5% of CSA expansive additives and 15:5(F.A:S.F)are replaced at unit cement content, high performance concrete with both good fluidity at fresh state and high compressive strength, compensation of drying and autogenous shrinkage at hardened state are accomplished.

개질 CaO계와 CSA계 팽창재를 혼합사용한 콘크리트의 건조수축 및 균열복구 성능평가에 관한 연구

송태협,박지선,김대봉 한국방재학회 2016 한국방재학회논문집 Vol.16 No.6

Cracks in concrete structures are the most fundamental considerations for buildings. This study suggested the concrete mix that can suppress cracks caused by drying shrinkage that occurs in the early stage of concrete placement and help cracks heal themselves. Towards this purpose, the basic physical properties of mortar mix with a mixture of reformed CaO and CSA-based admixture were verified, and then applied to the concrete mix in order to evaluate the drying shrinkage and crack recovery performance. In addition, a comparative verification of the performance with concrete utilizing expansive admixture which are currently used in Japan was conducted to investigate the possibility of commercialization of the concrete mix performed. From the experimental results, the concrete mix proposed in this study showed two times increase in performance compared to plain concrete, and it also exhibited the performance increase of maximum 70%, respectively even in comparison with commercial products in reduction of the drying shrinkage and crack recovery performance. 콘크리트 건축물에서의 균열은 건축물의 안전성을 확보하기 위한 가장 기초적인 고려사항이다. 본 연구에서는 콘크리트 건축물의 콘크리트 타설초기 발생하는 건조수축에 의한 균열의 발생을 억제하고 이미 발생된 균열을 스스로 치유할 수 있는 콘크리트 배합을 제시하고자 하였다. 이를 위하여 개질 CaO와 CSA계 팽창재를 혼합한 모르타르 배합을 제시하고 이에 대한 기본적인 물성검증 후, 콘크리트 배합에 적용하여 건조수축과 균열회복 성능을 평가하였다. 아울러, 본 연구에서 수행한 콘크리트 배합의 상용화 가능성을 확인해보고자 현재 일본에서 상용중인 팽창재를 활용한 콘크리트와의 성능을 비교·검증하였다. 실험결과로부터 본 연구에서 제안한 콘크리트 배합은 건조수축의 저감과 균열회복 성능에서 일반 콘크리트 대비 모두 최대 약 2배의 성능향상을 나타내었으며 상용제품과의 성능비교에서도 각각 약 70%의 성능향상을 나타내었다.

CSA 팽창재 치환율에 따른 시멘트계 그라우트의 물리적 특성 평가

이재승,노상균,김경훈,신홍철 대한건축학회지회연합회 2022 대한건축학회연합논문집 Vol.24 No.5

Grout is used for filling joint of concrete structures, and it is required to have fluidity, required strength and shrinkage reduction performance. However, in cement-based grout, drying shrinkage is inevitable due to evaporation of surplus water during hydration reaction. Therefore, in this study, the physical properties of cement-based grout according to the replacement ratio of CSA expansion admixture were analyzed to reduce drying shrinkage. As an experimental results, fluidity increased as the replacement ratio of the expansion admixture increased, and the setting time accelerated as the replacement ratio of the expansion admixture increased. In terms of compressive strength, the initial compressive strength increased by about 7 % when the replacement ratio of the expansion admixture was 3 to 6 %, other than that, the compressive strength decreased as the replacement ratio of the expansion additve increased, so the target strength was not satisfied with the replacement ratio of the expansion admixture of 15 %. The expansion height was contracted(-) up to 6%, and the replacement ratio of 9% or more was expanded(+). The length change in drying shrinkage decreased as the replacement ratio of the expansion admixture increased, and increased as the curing temperature increased. However, compared with the replacement ratio of 0 %(Plain), the higher curing temperature, the better the compensation effect for shrinkage. As a result, it was found that the use of 9 to 12% of the expansion admixture was appropriate within the scope of this study.0

Characterizations of High Early-Strength Type Shrinkage Reducing Cement and Calcium Sulfo-aluminate by Using Industrial Wastes

Lee, Keon-Ho,Nam, Seong-Young,Min, Seung-Eui,Lee, Hyoung-Woo,Han, Choon,Ahn, Ji-Whan The Korean Ceramic Society 2016 한국세라믹학회지 Vol.53 No.2

In this study, the utilization of the by-products of various industries was examined using raw materials of CSA high-functional cement such as coal bottom ash, red mud, phosphate gypsum, etc. Technology to improve energy efficiency and reduce $CO_2$ was developed as part of the manufacturing process; this technology included lower temperature sintering ($150{\sim}200^{\circ}C$) than is used in the OPC cement manufacturing process, replacement of CSA cement with the main raw material bauxite, and a determination of the optimum mix condition. In order to develop CSA cement, a manufacturing system was established in the Danyang plant of the HANIL Cement Co. Ltd., in Korea. About 4,200 tons of low purity expansion agent CSA cement (about 16%) and about 850 tons of the lime-based expansion agent dead burned lime (about 8%) were produced at a rate of 60 tons per hour at the HANIL Cement rotary kiln. To improve the OPC cement properties, samples of 10%, 13%, and 16% of CSA cement were mixed with the OPC cement and the compressive strength and length variation rate of the green cement were examined. When green cement was mixed with each ratio of CSA cement and OPC cement, the compressive strength was improved by about 30% and the expansibility of the green cement was also improved. When green cement was mixed with 16% of CSA cement, the compressive strength was excellent compared with that of OPC cement. Therefore, this study indicates the possibility of a practical use of low-cost CSA cement employing industrial wastes only.