• 자원리싸이클링
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• 제23권3호
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• pp.13-20
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• 2014

현재 산업 및 토목기술의 발전으로 인한 콘크리트 구조물의 대형화 및 다양화가 시도되고 있으나 대형 구조물의 시공 시 발생하는 수화열은 온도균열을 유발하여 콘크리트 구조물의 내구성능을 저하시키는 문제를 발생한다. 본 논문은 시멘트의 종류에 따른 콘크리트의 내구성능 및 수화열 저감 특성을 고찰하기 위하여 보통포틀랜드시멘트, 플라이애쉬를 혼합한 2성분계 시멘트, 플라이애쉬와 고로슬래그를 혼합한 3성분계 시멘트 및 저발열 시멘트를 각 각 사용하여 제작한 콘크리트의 물성, 내구성능 및 수화특성 등의 결과를 비교 분석한 결과, 3성분계 혼합 시멘트가 내구성능 및 수화열 저감 효과에 가장 우수한 것으로 나타나 매스 콘크리트 및 내구성능이 요구되는 구조물 축조에 적합하다고 판단되었다.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2010년도 추계학술대회 초록집
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• pp.131.1-131.1
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• 2010

This study was conducted for engineering optimization for the gasification process which is the key factor for success of Taean IGCC gasification plant which has been driven forward under the government support in order to expand to supply new and renewable energy and diminish the burden of the responsibility for the reduction of the green house gas emission. The gasification process consists of coal milling and drying, pressurization and feeding, gasification, quenching and HP syngas cooling, slag removal system, dry flyash removal system, wet scrubbing system, and primary water treatment system. The configuration optimization is essential for the high efficiency and the cost saving. For this purpose, it was designed to have syngas cooler to recover the sensible heat as much as possible from the hot syngas produced from the gasifier which is the dry-feeding and entrained bed slagging type and also applied with the oxygen combustion and the first stage cylindrical upward gas flow. The pressure condition inside of the gasifier is around 40~45Mpg and the temperature condition is up to $1500{\sim}1700^{\circ}C$. It was designed for about 70% out of fly ash to be drained out throughout the quenching water in the bottom part of the gasifier as a type of molten slag flowing down on the membrane wall and finally become a byproduct over the slag removal system. The flyash removal system to capture solid particulates is applied with HPHT ceramic candle filter to stand up against the high pressure and temperature. When it comes to the residual tiny particles after the flyash removal system, wet scurbbing system is applied to finally clean up the solids. The washed-up syngas through the wet scrubber will keep around $130{\sim}135^{\circ}C$, 40~42Mpg and 250 ppmv of hydrochloric acid(HCl) and hydrofluoric acid(HF) at maximum and it is turned over to the gas treatment system for removing toxic gases out of the syngas to comply with the conditions requested from the gas turbine. The result of this study will be utilized to the detailed engineering, procurement and manufacturing of equipments, and construction for the Taean IGCC plant and furthermore it is the baseline technology applicable for the poly-generation such as coal gasification(SNG) and liquefaction(CTL) to reinforce national energy security and create new business models.

• 콘크리트학회논문집
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• 제19권4호
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• pp.393-399
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• 2007

교량 바닥판은 공용 기간 동안 차량하중 및 다양한 환경 조건 (동결융해, 우수 및 융빙제)에 직접적으로 노출되어 있는 부재이다. 이로 인해, 교량 바닥판은 다른 주요부재에 비해서 다양한 결함 및 손상이 자주 발생하여 고속도로 상의 문제 교량은 대부분 바닥판에 결함을 지니고 있다. 따라서 교량 바닥판의 내구성을 확보하기 위한 방안으로 고성능콘크리트 (high performance concrete, HPC)가 대안으로 제시되었다. 교량 바닥판의 내구성을 향상하기 위해, 배합된 고성능콘크리트에 대한 내구성능 실험이 수행되었다. 본 연구에 사용된 배합 변수는 총 4가지로, 1) 보통시멘트 (OPC) 2) 시멘트 중량의 20%의 플라이애쉬 치환(FA), 3) 20%의 플라이애쉬와 4%의 실리카퓸 치환 (FS), 그리고 4) 40%의 고로슬래그미분말 치환 (BS)에 대해서 내구성 실험을 실시한 후 비교 평가를 실시하였으며, 사용된 설계 압축강도는 각각 27 MPa와 35 MPa이다. 고성능콘크리트를 시험 배합한 결과, 결합재의 양을 증가시켜 강도를 증진시키는 것보다는 혼화재를 사용하는 것이 내구 성능이 크게 향상되는 것으로 나타났다. 특히 혼화재 중, 플라이애쉬와 실리카퓸을 함께 결합재로 사용하는 경우가 균열 저감 및 내구 성능 증진에 가장 효율적인 것으로 나타났다.

• 한국건축시공학회지
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• 제5권3호
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• pp.101-107
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• 2005

This paper reports the contribution of Shrinkage reducing admixture(SRA) to the physical properties and drying shrinkage of concrete. Dosage of SRA is varied with. For the properties of fresh concrete, an increase in SRA dosage results in a decrease in fluidity and air content, while setting time is accelerated. For the properties of hardened concrete, the incorporation of mineral admixture leads to a decrease in compressive strength at early age, whereas after 28 days, the incorporation of fly ash(FA) and blast furnace slag(BS) has greater compressive strength than conventional concrete without admixture. The use of SRA results in a decrease in compressive strength. The incorporation of SRA with every $1\%$ increase causes the decrease of compressive strength by as much as $3\~6\%$. For drying shrinkage properties, the incorporation of FA and BS reduces drying shrinkage slightly. The use of SRA also decreases drying shrinkage. Every $1\%$ of increase in SRA dosage can reduce drying shrinkage by as much as $10\~15\%$

• Computers and Concrete
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• 제19권6호
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• pp.651-658
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• 2017

High-performance concrete, besides aggregate, cement, and water, incorporates supplementary cementitious materials, such as fly ash and blast furnace slag, and chemical admixture, such as superplasticizer. Hence, it is a highly complex material and modeling its behavior represents a difficult task. This paper presents an evolutionary system for the prediction of high performance concrete strength. The proposed framework blends a recently developed version of genetic programming with a local search method. The resulting system enables us to build a model that produces an accurate estimation of the considered parameter. Experimental results show the suitability of the proposed system for the prediction of concrete strength. The proposed method produces a lower error with respect to the state-of-the art technique. The paper provides two contributions: from the point of view of the high performance concrete strength prediction, a system able to outperform existing state-of-the-art techniques is defined; from the machine learning perspective, this case study shows that including a local searcher in the geometric semantic genetic programming system can speed up the convergence of the search process.

• Computers and Concrete
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• 제19권6호
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• pp.717-724
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• 2017

In this paper, four formulas are proposed via gene expression programming (GEP)-based models and regression analysis (RA) to predict the flexural strength ($f_s$) values of mortars containing different mineral admixtures that are ground granulated blast-furnace slag (GGBFS), silica fume (SF) and fly ash (FA) at different ages. Three formulas obtained from the GEP-I, GEP-II and GEP-III models are constituted to predict the $f_s$ values from the age of specimen, water-binder ratio and compressive strength. Besides, one formula obtained from the RA is constituted to predict the $f_s$ values from the compressive strength. To achieve these formulas in the GEP and RA models, 972 data of the experimental studies presented with mortar mixtures were gathered from the literatures. 734 data of the experimental studies are divided without pre-planned for these formulas achieved from the training and testing sets of GEP and RA models. Beside, these formulas are validated with 238 data of experimental studies un-employed in training and testing sets. The $f_s$ results obtained from the training, testing and validation sets of these formulas are compared with the results obtained from the experimental studies and the formulas given in the literature for concrete. These comparisons show that the results of the formulas obtained from the GEP and RA models appear to well compatible with the experimental results and find to be very credible according to the results of other formulas.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표논문집(II)
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• pp.262-268
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• 1998

This research is to examine the selected method of optimal mixing proportion and cost analysis in the super flowing concrete. As confined water $ratio($\beta_p$)$ and K is introduced, itis to establish optimal mixing design of super flowing concrete according to the steps of paste, mortar and concrete. From paste and mortar test, it was led to $$\beta_p$$ and $K_p$satisfying the optimum condions depending on the kinds of binders. Then $$\beta_p$$ and $K_p$ is reflected to the mix condition of super flowing concrete. The result of test, the mix condition of super flowing concrete satisfied the quality performance of concrete with adjustment of additional rate of the superplasticizer. Besides, in case of design strength $350kg/\textrm{cm}^2$ of concrete, material cost in super flowing concrete is able to be reduced 5~16% in replacement of fly ash 30% in ordinary portland cement and slag cement.

• 한국건축시공학회지
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• 제7권4호
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• pp.145-151
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• 2007

In this paper, tests are carried out in order to investigate the strength development of concrete under various binder types, W/B and curing temperature ranged from $5{\sim}20^{\circ}C$. Fly ash and blast furnace slag were incorporated by as much as 30%, respectively. Strength development of concrete are estimated using Logistic model and strength ratio of concrete at 28days to that at early age are also investigated. According to experimental results, it is found that good agreements are obtained between measured values and calculated ones using logistic model below $20^{\circ}C$. Strength ratio of concrete at 28days to that at early age increases in case W/B decreases and curing temperature increases. Tables and graphs for strength ratio of concrete are provided in this paper. It is capable of obtaining and predicting the periods to attain design strength by considering increment factor of strength easily with the table and graphs presented in this paper. This paper presents the reference data to decide removal time of form, time to reach target strength and strength inspection of remicon whether the test specimens meet the specified criteria of compressive strength. Multi regression models with respect to the relationship between 7days compressive strength and 28 days compressive strength depending on W/B and admixture types are presented.

• 한국건축시공학회지
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• 제7권2호통권24호
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• pp.59-65
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• 2007

Recently, due to the increase of high-rise buildings construction, many researches for making harden of concrete earlier and remove of forms faster are being performed to reduce construction period. In this study, we compared and analysed the early strength properties of mortar according to the kinds and replacement ratio of mineral admixture to select the kinds and replacement ratio of mineral admixture of high early strength concrete. For this purpose, mortar mixtures according to the kinds(FA, MK, ZR, BFS, DM) and replacement ratio(0, 2, 4% by volume of sand) of mineral admixture were selected. From our test data, early-age compressive strength decreased in accordance with the increase of replacement ratio of fly-ash(FA) & blast furnace slag powder(BSF) and, in case of addition admixture, early-age compressive strength of with containing 4% appeared higher compared with containing 2%.

• Computers and Concrete
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• 제10권6호
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• pp.557-573
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• 2012

This paper discusses the combined application of two different techniques, Neural Networks (NN) and Principal Component Analysis (PCA), for improved prediction of concrete properties. The combination of these approaches allowed the development of six neural networks models for predicting slump and compressive strength of concrete with mineral additives such as blast furnace slag, fly ash and silica fume. The Back-Propagation Multi-Layer Perceptron (BPMLP) with Bayesian regularization was used in all these models. They are produced to implement the complex nonlinear relationship between the inputs and the output of the network. They are also established through the incorporation of a huge experimental database on concrete organized in the form Mix-Property. Thus, the data comprising the concrete mixtures are much correlated to each others. The PCA is proposed for the compression and the elimination of the correlation between these data. After applying the PCA, the uncorrelated data were used to train the six models. The predictive results of these models were compared with the actual experimental trials. The results showed that the elimination of the correlation between the input parameters using PCA improved the predictive generalisation performance models with smaller architectures and dimensionality reduction. This study showed also that using the developed models for numerical investigations on the parameters affecting the properties of concrete is promising.