• Computers and Concrete
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• 제22권3호
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• pp.319-326
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• 2018

RC (Reinforced Concrete) members are always subjected to loading conditions and have construction joints when constructed on a big scale. Service life for RC structure exposed to chloride attack is usually estimated through chloride diffusion test in sound concrete, however the test is performed without consideration of effect of loading and joint. In the present work, chloride diffusion coefficient is measured in concrete cured for 1 year. In order to evaluate the effect of applied load, cold joint, and mineral admixtures, OPC (Ordinary Portland Cement) and 40%-replaced GGBFS (Ground Granulated Blast Furnace Slag) concrete are prepared. The diffusion test is performed under loading conditions for concrete containing cold joint. Investigating the previous test results for 91 days-cured condition and the present work, changing diffusion coefficients with applied stress are normalized considering material type and cold joint. For evaluation of service life in RC continuous beam with 2 spans, non-linear analytical model is adopted, and service life in each location is evaluated considering the effects of applied stress, cold joint, and GGBFS. From the work, varying service life is simulated under various loading conditions, and the reduced results due to cold joint and tensile zone are quantitatively evaluated. The effect of various conditions on diffusion can provide more quantitative evaluation of chloride behavior and the related service life.

• 한국농공학회논문집
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• 제54권2호
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• pp.157-166
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• 2012

Most of the roads are paved with impermeable materials such as asphalt concrete and cement concrete, and in the event of heavy rainfall, rainwater directly flows into river through a drainage hole on the pavement surface. This large quantity of rainwater directly spilled into the river frequently leads to the flooding of urban streams, damaging lowlands and the lower reaches of a river. In recent years there has been a great deal of ongoing research concerning water permeability and drainage in pavements. Accordingly, in this research, a porous polymer concrete was developed for permeable pavement by using unsaturated polyester resin as a binder, recycled aggregate as coarse aggregate, fly ash and blast furnace slag as filler, and its physical and mechanical properties were investigated. Also, 3 types of permeable polymer block by optimum mix design were developed and rainfall runoff reduction effects by permeability pavement using permeable polymer block were analyzed based on hydraulic experimental model. The infiltration volume, infiltration ratio, runoff initial time and runoff volume in permeability pavement with permeable polymer block of $300{\times}300{\times}80$ mm were evaluated for 50, 100 and 200mm/hr rainfall intensity.

• International Journal of Industrial Entomology and Biomaterials
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• 제26권1호
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• pp.41-46
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• 2013

The cladoceran Daphniamagna has been used as an aquatic test species in aquatic toxicology. To evaluate the aquatic toxicity of leachate from concrete, the immobilization of D. magna was observed after treatment of various concentrations of leachate specimens. Reliabilities of the culture condition and the experimental protocol for acute toxicity test were successfully achieved from the standard toxicity test. The leachates were prepared from the mixture of Ordinary Portland Cement (OPC) and pozzolanic admixtures, Pulverised fuel ash (PFA), Ground granulated blast furnace slag (GGBS) and GGBS containing loess. Acute toxicity test showed 100% immobilization of D. magna for OPC or PFA. The leachates from OPC or PFA had high pH 10 to 12. However, GGBS and GGBS containing loess showed less toxicity according to the concentrations. Especially, immobilization was not observed at the concentrations below 12.5% of GGBS containing loess. Also the range of pH for these specimens was 8 to 9. This suggested that the use of loess as the admixture in concrete may be useful to reduce eco-toxicity of leachates from concrete. This our study provided the harmfulness of the alkali leaching from concrete in aquatic environment and the usefulness of D. magna to evaluate the toxicity of leachates from concrete.

• 콘크리트학회논문집
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• 제12권3호
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• pp.47-55
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• 2000

Protections from the frost damage at early ages are one of the serious problems to be considered in cold weather concreting. Frost damage at early ages brings about the harmful influences on the concrete structures such as surface cracks and declination of strength development. Therefore, in this paper, protecting periods of frost damage at early ages according to the standard specifications provided in KCI(Korean Concrete Institute) are suggested by appling logistic curve, which evaluates the strength development of concrete with maturity. W/B, kinds of cement and curing temperatures are selected as test parameters. According to the results, the estimation of strength development by logistic curve has a good agreement between calculated values and measured values. As W/B and compressive strength for protecting from frost damages at early ages increase, it is prolonged. It shows that the protecting periods of FAC(Fly Ash Cement) and BSC(Blast-furnace Slag Cement) concrete are longer than those of OPC(Ordinary Portland Cement) concrete. The protecting peridos from frost damage at early age by JASS are somewhat shorter than those by this paper.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.743-747
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• 2005

In South Korea, about 900 metal mines have been abandoned, and about 88 million-t metal mine wastes have been discarded in recent years. The treatment of the tailings which are the main wastes in the abandoned metal mines becomes a social problem because they cause environmental pollution such as acidic waste water generation, groundwater contamination, and dust generation. Since almost whole quantities of the tailings have disposed by landfill now, the development of effective recycling methods for the tailings are strongly requested. It is expected that the fine tailings obtained by centrifugal separation process among the tailings can be utilized as admixture for cement. The purpose of this study is to evaluate the micro-structure of cement mortar admixed with fine tailing. Various admixtures were made of Fine tailings and 2 Types of OPC, fly-ash and blast furnace slag. The hydration reactivity of cement mortar with FT was examined by Porosity, XRD and SEM morphology analysis. The anolytical result about hardened hydrates shows that waste fine tailing help hydrates none densified due to it,s filling-space, These densified effect is concluded with improving the resistance to attack of cement mortar including waste fine tailing.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.565-568
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• 2008

플라이애쉬는 상대적으로 낮은 초기 강도 발현율에 의해서 고로슬래그 미분말에 비하여 사용이제한적이다. 따라서 플라이애쉬는 우수한 경제성과 많은 발생량에도 불구하고 많은 양이 활용되지 못하고 매립되고 있다.본 연구에서는 자극제가 플라이애쉬를 사용한 콘크리트의 성능에 미치는 영향을 확인하고 플라이애쉬의 활용 증대 가능성을 검토하였다. 연구 결과 자극제를 사용한 플라이애쉬 콘크리트가 동일 슬럼프, 공기량 및 로스를 가지면서 일반적인 혼화제를 사용한 콘크리트보다 압축강도가 높게 나타났으며 다양한 요인에서의 자극제의 성능 발현을 검증할 경우 자극제를 사용한 플라이애쉬 콘크리트의 현장 적용 확대가 가능할 것으로 사료된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.569-572
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• 2008

본 연구에서는 시멘트와 광물질 혼화재인 고로슬래그미분말과 플라이애시를 미리 혼합한 프리믹스 혼합시멘트와 이들 재료를 각각 투입하여 제작한 콘크리트에 대하여 보통강도 및 고강도 영역에서의 압축강도와 염화물 확산계수를 측정하고 각각에 대한 품질편차를 검토하였다. 검토 결과 프리믹스 혼합시멘트를 사용한 콘크리트가 재료를 각각 투입하여 제조한 콘크리트에 비하여 보통강도 및 고강도 영역 모두에서 압축강도 평균값은 증가하고 표준편차는 감소하는 것으로 나타났으며, 염화물 확산계수의 경우 평균값과 표준편차가 모두 감소하는 경향을 나타냈다. 향후 고강도 영역에서의 압축강도 변동폭 및 보통강도 영역에서의 내구성 변동폭을 감소시키기 위해 프리믹스 혼합시멘트를 사용하는 것이 바람직한 것으로 판단된다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.401-404
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• 2008

균열은 콘크리트에 염소이온과 같은 유해한 물질의 침투경로가 되어 내구성에 심각한 열화를 야기한다. 따라서 고내구성 재료를 사용한 콘크리트 휨부재에서의 균열 발생에 따른 염소이온 침투특성을 검토하고자 하였다. 이를 위해, 고내구성 재료를 적용한 보에 하중을 가하여 휨균열을 도입시키고, 촉진 염화물 침투실험(RCPT)과 장기 염화물 침투실험을 실시하여 염화물 침투 특성을 파악하였다. 실험결과에 따르면, 고내구성 재료를 적용한 부재는 균열이 발생하여도 일반 콘크리트 부재에 비해 높은 염화물 침투 저항성을 보였다. 특히 고로슬래그 미분말을 적용한 경우, 균열 부재의 장기 염화물 침투 실험에서 탁월한 염화물 침투 저항성을 보였다.

• 한국해양공학회지
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• 제28권2호
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• pp.140-146
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• 2014

This study investigated the engineering characteristics of non-sintering binder-stabilized mixtures consisting of different ratios of a hardening agent(3%, 6%, 9%, 12%) for recycling industrial by-products through several series of laboratory tests. The hardening agents consisted of two kinds of non-sintering binders(NSB-1, NSB-2), which were developed by using inter-chemical reactions among blast furnace slag, phospho-gypsum, and an alkali activator. In addition, ordinary Portland cement(OPC) was used to compare the engineering characteristics of the stabilized mixture. An unconfined compressive test showed that the unconfined compressive strength increased with the curing time and mixing ratio. Experimental test results indicated that the 7-day strength of the NSB-1 mixture was similar to that of the OPC mixture. However, its 28-day strength was higher than that of the OPC mixture. The secant module of elasticity showed a range of $E_{50}=(42-109)q_u$ regardless of the agents. Based on the results of triaxial tests, the cohesion and friction angle increased with the mixing ratio.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2014년도 춘계 학술논문 발표대회
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• pp.146-147
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• 2014

In this study, as the resistance of the carbonation for high volume admixture incorporating concrete, coating effect of using refined cooking oil in the surface of high volume admixture incorporating concrete has been tested. The following results could be made as the conclusion. For the fresh concrete, the slump and air content has been identified as satisfying the target range. For the hardened concrete, comparing with specimen of Plain, specimen with coating showed better long age compressive strength. For the carbonation speed, the specimen of FA30 showed highest speed and the specimen of BS60 showed higher speed than specimen of Plain. For all the specimens coated with RCO, as the decrease of capillary pores inside the concrete, the carbonation speed has been obviously decreased and with even better effect than using PEP coating. It could be identified that specimens with coating by RCO showed good effect on refrain the speed of carbonation.