• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.33-36
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• 2005

Recently, the use of volcanic-ash as a part of cement content in concrete is very common. But, it has been indicated that the compressive strength of concrete using large amount of volcanic-ash as a part of cement content in early age is low and carbonation velocity is fast. To solve those problems, High Volume Volcanic-Ash Concrete which contained large amount of volcanic-ash as a part of fine aggregate has been proposed. This is an experimential study to compare and analyze the properties of High Volumn Volcanic-Ash Concrete according to the replacement method and ratio of volcanic-ash. For this purpose, the mix proportion of concrete according to the replacement method(PL, C10, C150, A10, A100, A150) And then slump, setting time, bleeding, compressive strength, tensile strength and carbornation test were performed. According to test results, it was found that the compressive strength of the concrete using the volcanic-ash as a part of fine aggregate(A) was higher than that of the concrete using the volcanic-ash as a part of cement content(C). And, the compressive strength of the A concrete increased in early age as well as in long tern age as the volcanic-ash content increased.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2006년도 추계 학술논문 발표대회 논문집
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• pp.39-42
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• 2006

In this study, there is purpose that is on a concrete defect happen from aggregate minute's particle mixing in process that make waste concrete as recyclable cement puts to practical use constructing basic data for design of mix proportion used recyclable cement and solves strength fall problem using micron separator, and does general recyclable cement high quality. As a result of X-ray diffraction(XRD) of rater HR-C than NR-C is aware that it come out the micron-separating to decrease the $SiO_2$-peak below 50%. And a construction field which apply for strength's $24{\sim}28MPa$ HR-C in order to realize NR-C of 44% and 51%. Recycle concrete capacity through improved recycle cement of manufacturing technique by micron-separating's new distribution more better improvement. Therefore, in this study, it need to more various study a recycle cement of high quality for reasonable and utility recycling than disposal concrete.

• Computers and Concrete
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• 제16권3호
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• pp.343-356
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• 2015

1078 sets of mixtures in total that include fly ash, slag, and/or silica fume have been collected for prediction on concrete properties. A new database platform (Compos) has been developed, by which the stepwise multiple linear regression (SMLR) and BP artificial neural networks (BP ANNs) programs have been applied respectively to identify correlations between the concrete properties (strength, workability, and durability) and the dosage and/or quality of raw materials'. The results showed obvious nonlinear relations so that forecasting by using nonlinear method has clearly higher accuracy than using linear method. The forecasting accuracy rises along with the increasing of age and the prediction on cubic compressive strength have the best results, because the minimum average relative error (MARE) for 60-day cubic compressive strength was less than 8%. The precision for forecasting of concrete workability takes the second place in which the MARE is less than 15%. Forecasting on concrete durability has the lowest accuracy as its MARE has even reached 30%. These conclusions have been certified in a ready-mixed concrete plant that the synthesized MARE of 7-day/28-day strength and initial slump is less than 8%. The parameters of BP ANNs and its conformation have been discussed as well in this study.

• Computers and Concrete
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• 제11권6호
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• pp.587-602
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• 2013

In the current study, a method for concrete compressive strength prediction (based on cement strength class), incorporated in a software package developed by the authors for the estimation of concrete service life under harmful environments, is presented and validated. Prediction of concrete compressive strength, prior to real experimentation, can be a very useful tool for a first mix screening. Given the fact that lower limitations in strength have been set in standards, to attain a minimum of service life, a strength approach is a necessity. Furthermore, considering the number of theoretical attempts on strength predictions so far, it can be seen that although they lack widespread accepted validity, certain empirical expressions are still widely used. The method elaborated in this study, it offers a simple and accurate, compressive strength estimation, in very good agreement with experimental results. A modified version of the Feret's formula is used, since it contains only one adjustable parameter, predicted by knowing the cement strength class. The approach presented in this study can be applied on any cement type, including active additions (fly ash, silica fume) and age.

• 대한안전경영과학회지
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• 제13권2호
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• pp.275-282
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• 2011

A core device of foam system is the in-line eductor and it is the device to mix the foam liquid into liquid solution proper to the use density and the mixture ratio must be kept regularly regardless of changing fluid condition of the front and rear end of the in-line eductor. However, if the flux of the pressurized water changes, the mixture ratio is not kept regularly, and so it becomes a cause which a performance of fire-extinguishing deteriorates in discharging foam liquid. I devise a method to improve it that the metering orifice type in-line eductor is improved into the metering venturi type in-line eductor, the fluctuation of the mixture ratio to the flux change of the pressurized water is minimized and the performance of fire-extinguishing is kept regularly. As this method is simple in its structure and can be designed at a low cost, it helps for maintenance as well. In the future, it seems to need the research for the metering nozzle type in-line eductor in the future.

• 한국신뢰성학회지:신뢰성응용연구
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• 제17권4호
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• pp.332-342
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• 2017

Purpose: In this study, the lifetime distribution of a k-out-of-n system with heterogeneous components is suggested as Markov model, and the time-to-failure (TTF) distribution of each component is considered as phase-type distribution (PHD). Furthermore, based on the model, a redundancy allocation problem with a mix of components (RAPMC) is proposed. Methods: The lifetime distribution model for the system is formulated by the structured Markov chain. From the model, the various information on the system lifetime can be ascertained by the matrix-analytic (or-geometric) method. Conclusion: By the generalization of TTF distribution (PHD) and the consideration of heterogeneous components, the lifetime distribution model can delineate many real systems and be exploited for developing system operation policies such as preventive maintenance, warranty. Moreover, the effectiveness of the proposed RAPMC is verified by numerical experiments. That is, under the equivalent design conditions, it presented a system with higher reliability than RAP without component mixing (RAPCM).

• Advances in concrete construction
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• 제7권3호
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• pp.143-150
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• 2019

This study presents the fracture properties of nano modified medium strength concrete (MSC). The nano particle used in this study is nano silica which replaces cement about 1 and 2% by weight, and the micro steel fibers are added about 0.4% volume of concrete. In addition to fracture properties, mechanical properties, namely, compressive strength, split tensile strength, and flexural strength of nano modified MSC are studied. To ensure the durability of the MSC, durability studies such as rapid chloride penetration test, sorptivity test, and water absorption test have been carried out for the nano modified MSC. From the study, it is observed that significant performance improvement in nano modified MSC in terms of strength and durability which could be attributed due to the addition pozzolanic reaction and the filler effect of nano silica. The incorporation of nano silica increases the fracture energy about 30% for mix without nano silica. Also, size independent fracture energy is arrived using two popular methods, namely, RILEM work of fracture method with $P-{\delta}$ tail correction and boundary effect method. Both the methods resulted in nearly the same size-independent $G_F$ irrespective of the notch to depth ratio of the same specimen. This shows evidence that either of the two procedures could be used in practice for analysis of cracked concrete structures.

• 한국지반공학회논문집
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• 제22권12호
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• pp.25-31
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• 2006

본 논문에서는 주열식말뚝 배면의 차수를 목적으로 쓰이는 SCM공법의 지반강도와 투수계수 개선 효과를 연구하였다. SCM공법은 2중관 롯드를 사용하여 중압($981{\sim}9,810kPa$)으로 지반을 절삭하고 충전 및 혼합하는 공법이다. 이는 시멘트와 알카리용탈이 최소화된 친환경적인 약액을 사용하는 것으로 실험을 통하여 입증하였다. 1축압축시험, 어독성시험 등을 통하여 화학적인 안정성을 실험하였고, 그 결과 내구성이 높고 조기강도 발현이 되며 알칼리용탈이 최소화된 친환경적인 약액재료임을 입증하였다. 그리고 현장시험을 통하여 구근과 차수벽이 형성됨을 확인하였다.

• 한국식생활문화학회지
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• 제23권5호
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• pp.595-604
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• 2008

This study was conducted to evaluate the menu of a Japanese restaurant in a first class tourism hotel. The calculations used for the menu analysis were conducted using MS Excel 2003. Several previous studies have been conducted to analyze menus. For example, Pavesic used of the weighted contribution margins (WCM) and potential food cost (PFC%) to evaluate menus, while Kasavana & Smith used the mix margin (MM%) and unit contribution margin (CM) to evaluate menus. The menu engineering method focused on the customer's viewpoints, while the Cost/Margin analysis method considered the manager's viewpoints. The menus that need continuous keeping Kasavana & Smith (Star) and Pavesic (Standard) included 'Assorted sashimi with side dishes (big), 'Lunch box special', 'Tempura course', 'Broiled Spanish mackerel and side dishes', 'Shrimp tempura', 'Special sushi', 'Seafood Udong', 'Buckwheat noodles'. The results of this study should increase customer satisfaction and profits at the Japanese Restaurant.

• 한국식생활문화학회지
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• 제21권3호
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• pp.270-279
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• 2006

This study was designed to : (a) analyze the menus of the French restaurant in tourism hotel using the menu analysis techniques of Kasavana & Smith and Pavesic, (b) compare the characteristics of the two analysis techniques. The calculations for the menu analysis were done using the MS 2000 Excel spreadsheet program. The menu mix % and unit contribution margin were used as variables by Kasavana & Smith and weighted contribution margins (WCM) and potential food cost % (PFC%) by Pavesic. In two cases, a four-cell matrix was created and menu items were located in each according they achieved high or low scores with respect to two variables. The items that scored favorably on both variables were rated in the top category (e.g., star, prime) and those that scored below average on both were rated in the lowest category (e.g., dog, problem). While Kasavana & Smith's method focused on customer's viewpoints, Pavesic's method considered the manager's viewpoints. Therefore, it is more likely to be desirable for decision-making on menus if the menu analysis techniques chosen is suited to its purpose.