자연 및 인위적 처리방법 변화에 따른 순환잔골재의 pH저감

한천구,한민철,한상윤,Han, Cheon-Goo,Han, Min-Cheol,Han, Sang-Yoon 한국건설순환자원학회 2011 한국건설순환자원학회지 Vol.6 No.1

본 연구는 폐콘크리트로부터 발생한 성토 복토용 순환잔골재의 pH 저감을 목적으로 자연적 처리 방법 및 인위적 처리 방법을 이용하여 순환잔골재의 pH 저감특성을 비교 분석 하고자 하였는데, 그 결과를 요약하면 다음과 같다. 실내방치된 순환잔골재의 경우는 사람의 호흡 등 대기중 높은 $CO_2$농도로 인해 실외방치된 순환잔골재보다, 또한 쌓기 두께가 얇을수록 pH를 저감시킨 것으로 분석된다. 공기투과의 경우 비교적 순환잔골재의 pH저감이 효과적이었는데 이는 고압의 환풍기로 인해 순환잔골재에 원활한 $CO_2$ 공급으로 pH를 저감시킨 것으로 판단된다. 살수처리의 경우 미수화 시멘트의 수화반응을 촉진시켜 수산화칼슘을 용해시키고, 건조과정중 대기중 $CO_2$에 의한 중성화로 pH를 크게 저감시키는 것으로 나타났으며 침수처리에서는 pH 저감 효과가 미흡하였다. $CO_2$촉진의 경우 순환잔골재의 pH저감 효과가 가장 우수한 것으로 나타났는데, 이는 원활한 $CO_2$공급이 가능하기 때문인 것으로 분석된다. 이상의 실험 결과를 종합하면, pH 저감성능, 경제성 및 작업성 측면을 고려할 경우 순환잔골재 질량비 1: 0.5 비율로 살수한 다음, 강제적인 $CO_2$가스의 처리로 건습을 반복한다면 순환잔골재의 pH저감에 가장 효과적인 방법이 될 것으로 분석된다. This study is to comparatively analyze the characteristics of pH decrease in recycled fine aggregates for embankment and landfill produced from waste concrete by using natural process and artificial process. The result was as follows In case of recycled fine aggregates left outdoor, it was found that pH level was decreased if the thickness of embankment becomes thinner, or the materials left outdoors owing to high concentration of $CO_2$ in atmosphere caused by respirations of people. When the air was permeated, pH level was decreased more effectively. It was analyzed that this phenomenon was caused by efficient supply of $CO_2$ in the recycled fine aggregates owing to high-pressure ventilators. In case of water spraying treatment, sprayed water facilitated hydration of unhydrated cement to dissolve calcium hydroxides which neutralized $CO_2$ in the atmosphere during desiccation process and decrease pH level by a considerable margin. In case of Immersed treatment, decrease of pH was not sufficient. When facilitating the supply of $CO_2$, pH level of the recycled fine aggregates was decreased by the largest margin. It was analyzed that this phenomenon was caused by efficient supply of $CO_2$. From the above results, it was analyzed that the most effective method of reducing pH level of the recycled fine aggregates from the aspects of pH reduction performance, economic efficiency and workability was repeated wet-dry cycles of spraying water to the aggregates in the proportion of 1:0.5 by weight and then treating by forcefully blowing $CO_2$ gas into the aggregates.

건조수축 저감형 유동화제 및 2 중 버블시트를 사용한 콘크리트의 현장적용

한천구,오치현,신재경,Han, Cheon-Goo,Oh, Chi-Hyun,Shin, Jae-Kyung 한국건축시공학회 2007 한국건축시공학회지 Vol.7 No.1

This study investigates the filed application in Daebul Free Trade Zone applying both a flowing method using drying shrinkage-reducing superplasticizer(SRS) and an insulating curing method using double layer bubble sheet. Test results showed that fresh concrete satisfied target slump and air content. A structure adding SRS significantly decreased the total bleeding capacity and accelerated the setting time. As for the crack occurrence, the structure applying the flowing method and double bubble sheets simultaneously exhibited the most favorable crack endurance, while conventional concrete showed more than 1mm size of crack in overall. In addition, a structure applying the flowing concrete method partially presented the micro crack. For the area proportion of crack occurrence, the structure using the double bubble sheets indicated 9.8%, while others applying flowing concrete method was 28%, compared with that of conventional one. For the compressive strength of specimens, standard curing specimens indicated $3{\sim}33%$ higher value than that of specimens cured besides the field construction. The specimens containing SRS improved the strength of $2{\sim}6MPa$, which is $10{\sim}22%$ higher than that of conventional concrete.

회귀분석에 의한 CSA계 팽창재를 사용한 콘크리트의 건조수축 예측방법 검토

한천구,한민철,박천진,Han, Cheon-Goo,Han, Min-Cheol,Park, Chun-Jin 대한건축학회 2011 대한건축학회논문집 Vol.27 No.9

This paper is to propose the estimation model for the drying shrinkage of the concrete incorporating CSA based expansive additive(EA) by applying regression analysis. For concrete mixtures, EA and water contents are varied to monitor the effect of these variable on the reduction of drying shrinkage. JSCE, ACI and CEB-FIP models are applied to estimate the drying shrinkage in this paper. According to results, as expected, an increase in EA contents and a decrease in water contents resulted in a reduction of drying shrinkage. For the estimation of drying shrinakge, correction coefficients ${\alpha}$, ${\beta}$ and ${\gamma}$ in terms of EA contents to consider the effect of EA is added to JSCE model. Existing model for drying shrinkage such as ACI, CEB-FIP and JSCE model did not consider the effect of EA. Based on correction coefficient in terms of EA contents, modified JSCE model had better agreement with calculated and measured ones in estimating drying shrinkage of concrete incorporating EA based on nonlinear regression method within the sphere of the paper. Further investigation is needed to get improved accuracy and consider various type of EA.

순환골재 활용을 위한 품질시험

한천구,Han, Cheon-Goo 한국건설순환자원학회 2006 한국건설순환자원학회지 Vol.2 No.1

ERCO 혼입시기 및 혼입율 변화가 HPFRCC의 자기수축저감 및 기초적 특성에 미치는 영향

한천구,이제현,Han, Cheon-Goo,Lee, Je-Hyun 한국건축시공학회 2018 한국건축시공학회지 Vol.18 No.4

전 세계적으로 폭발성 물질 사용 증가와 폭탄테러 등으로 인명 및 재산 피해가 증가하고 있는 추세이다. 이에 중요 건축물이나 군사시설에 방호 방폭 성능을 향상시킬 목적으로 섬유보강 고성능 시멘트 복합체(HPFRCC)에 대한 연구가 진행되고 있다. 그러나, HPFRCC의 자기수축 문제를 해결하기 위해 ERCO를 혼입하게 되면 높은 점성 및 지방분의 시멘트 알칼리와의 조기반응으로 유동성, 공기량 및 강도 등 품질저하의 문제점이 발생한다. 이에 본 연구에서는 기존에 도출된 HPFRCC의 최적 배합에 ERCO 혼입시기 및 혼입율 변화에 따른 HPFRCC의 자기수축저감 및 기초적 특성에 대해 분석하였다. 그 결과 모르타르 믹싱완료 후 ERCO를 0.5% 혼입하는 후혼입 방법이 유동성, 강도 및 자기수축저감 등의 HPFRCC의 품질 향상에 가장 효과적인 것으로 밝혀졌다. For the entire world, due to the increased risks of explosion and terrorisms, damages on human life and properties have been increased. Regarding this issue, research on high performance fiber reinforced cementitious composite (HPFRCC) with the protecting performance for the building structures or military facilities against explosion or bombing has been increased (important). Among a series of the research, using emulsified refined cooking oil(ERCO) to reduce the autogenous shrinkage may cause some adverse effect on performance of the mixture such as increased viscosity, decreased fluidity, air content, and strength. Hence, in this research, based on the optimum design of HPFRCC induced by previous research, the influence of ERCO adding timing and dosage on autogenous shrinkage and fundamental properties were analyzed. As a result, it was revealed that 0.5% of ERCO should be added right after the mixing is most effective for the quality of HPFRCC such as fluidity, strength development and autogenous shrinkage reducing.

고로슬래그 미분말과 순환잔골재를 사용하는 무 시멘트 모르타르의 특성에 미치는 순환골재 미분말의 영향

한천구,손석헌,박경택,Han, Cheon-Goo,Son, Seok-Heon,Park, Kyung-Taek 대한건축학회 2011 대한건축학회논문집 Vol.27 No.6

This study is to investigate experimentally the effect of the use of recycled aggregate powder(RP) on the properties of mortar using recycled fine aggregates(RA) and blast furnace slag powder(BS) without portland cement. The results can be summarized as follows : For the fresh mortar, an increase in RP contents leads to increase W/B, Air contents increase gradually below 100 % of RP contents. As the RP contents increase, the compressive strength decrease gradually. Besides, as the RP contents increase, the strength deviation with curing temperature is negligible at 91 days, compressive strength at $20^{\circ}C$ was higher than that at $35^{\circ}C$. The flexural strength show a similar trend to the compressive strength in general, and the ratio of compressive strength to flexural strength is distributed within 1/1 ~ 1/3 in general, which is higher than the range of ordinary concrete. Meanwhile, as a result estimation of strength development, as the RP contents increase, the strength development trend is weakened gradually, but elapse with age, in case of RP 25 % show that strength level has similar with BS 100 %. It is thought that substition of RP for BS will be available for securing quality improvement within 25 %.

권두시론 - 그렇다면 땅에 묻으란 말인가?

한천구,Han, Cheon-Gu 한국시멘트협회 2007 시멘트 Vol.176 No.-

화재시 고성능 콘크리트의 폭렬방지 및 내화성능 향상

한천구,Han, Cheon-Gu 한국레미콘공업협회 2006 레미콘 Vol.7 No.-

레미콘 회수수에 안정화 처리한 콘크리트의 공학적 특성

한천구,이세현,우종환,이문환,Han, Cheon-Gu,Lee, Se-Hyeon,U, Jong-Hwan,Lee, Mun-Hwan 한국레미콘공업협회 2007 레미콘 Vol.1 No.-

석회암 순환잔골재를 사용한 고강도 콘크리트의 공학적 특성

한천구,김현우,Han, Cheon-Goo,Kim, Hyun-Woo 한국건설순환자원학회 2007 한국건설순환자원학회지 Vol.3 No.1

This study investigates the engineering properties of concrete incorporating lime stone crushed fine aggregate(Ls), which has been abandoned about 20% of total production due to the low purity. Test results showed that increase of Ls had favorable fluidity and slightly decreased air content. Bleeding capacity of all specimens was not appeared as those were high strength mixture proportion, but the specimens using more Ls accelerated initial and final setting. For the mechanical properties, specimens incorporating higher ratio of Ls, overall, resulted in increase of compressive strength, and exhibited very small inclined tendency in a dynamic elasticity modulus test In addition, for the durability properties, specimens incorporating higher Ls dramatically decreased a drying shrinkage and showed similar tendency in a frost & thaw test, as well as showing no more change in an accelerated neutralization test from the beginning. In conclusion, as it was confirmed in the experimental test, the high strength concrete applying Ls did not showed any problems in the aspects of engineering properties and mostly exhibited even more excellent quality than the specimens using natural fine aggregate.