• Computers and Concrete
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• v.24 no.2
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• pp.137-150
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• 2019

In this paper, surrogate models such as multivariate adaptive regression splines (MARS) and M5P model tree (M5P MT) methods have been investigated in order to propose a new formulation for the 28-days compressive strength of self-compacting concrete (SCC) incorporating metakaolin as a supplementary cementitious materials. A database comprising experimental data has been assembled from several published papers in the literature and the data have been used for training and testing. In particular, the data are arranged in a format of seven input parameters covering contents of cement, coarse aggregate to fine aggregate ratio, water, metakaolin, super plasticizer, largest maximum size and binder as well as one output parameter, which is the 28-days compressive strength. The efficiency of the proposed techniques has been demonstrated by means of certain statistical criteria. The findings have been compared to experimental results and their comparisons shows that the MARS and M5P MT approaches predict the compressive strength of SCC incorporating metakaolin with great precision. The performed sensitivity analysis to assign effective parameters on 28-days compressive strength indicates that cementitious binder content is the most effective variable in the mixture.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.6 no.4
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• pp.62-73
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• 2003

The study was to apply a mat style reed planting method at confluence to improve plants growth conditions by relaxing disturbed topographical base due to water flow and was intended to review the effect to build up a vegetation strip by monitoring process after the construction. First off, We've attempted to construct reed mats on selected sites as confluences of Tan and Gaehwa stream and then examined and analyzed characteristics of soil and vegetation community. As the results of the examination, the soil texture was proven to be a mix of sand and loamy sand and be 6.3 ~ 7.0 soil pH. In addition, it contained 1.0 ~ 4.6% of organic matter, 0.04 ~ 0.22% of T-N and 27.8 ~ 41.2% of water content. For its vegetation structure, the Tan stream confluence was first actually a point bar without plants prior to the construction but 8 kinds of hygrophytes including Persicaria hydropiper and 9 kinds of terrestrial plants such as Potentilla supina, Artemisia annua, and Alopecurus aequalis var. amurensis. On the other hand, the Gaehwa stream confluence contained 6 kinds of hygrophytes such as Bidens frondosa and other 11 kinds of terrestrial plants prior to the construction while it produced 7 kinds of hygrophytes including Ranunculus ternatus as well as Phragmites australis and 9 kinds of terrestrial plants such as Potentilla supina after the construction. For the Phragmites australis, almost of them was weathered away in early days just after planting because of development period passed, but on May, six months later from planting, it was investigated that its length was approximated as 65 ~ 85cm with 75% coverage and that the number of it was 437 ~ 633/$m^2$. The study was shown that reed mats can improve environmental conditions of disturbed topographical base, enabling natural growth of various riparian vegetation including the introduced plant, reed. In the meantime, it was supposedly judged that to recover or build up a vegetarian strip, supplementary materials should be prepared to help produce and grow plants because it is not probable to expect river drift by water flow at confluence and that corrosion, burying or inundation owing to changes of water lever should be considered.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.3
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• pp.292-298
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• 2016

In this research, considering the practical situation of separated placing method for mass concrete structure, an efficient method of controlling the heat of hydration is suggested by comparing between the simulated values and actual measurements conducted with the optimum mix design obtained from the various mix conditions with different types and amount of supplementary cementitious materials(SCMs). As the result of the research, firstly, the optimum mix designs for top and bottom layers were determined by Midas gen as OPC to FA of 85 to 15, and OPC to FA to BS of 50 to 20 to 30, respectively. The concrete mixtures prepared with the mix designs determined from the simulation satisfied the target performance range in slump, air content and compressive strength. Additionally, from temperature measurement for the actual mass concrete placed during spring, the maximum temperature difference between surface and core was about $10^{\circ}C$ with 59 and $49^{\circ}C$ for top and bottom layers, respectively, and 1.4 of cracking index was obtained. Therefore, considering the practical conditions of mass concrete construction, it is considered that the different heat of hydration method using different mix designs with SCMs can be an efficient method for controlling thermal cracking and settling cracking of mass concrete.

• The Korean Journal of Food And Nutrition
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• v.26 no.2
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• pp.208-215
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• 2013

This study for add functional nutrition ginseng to make consomm$\acute{e}$ soup of beef. consomm$\acute{e}$ soup of beef added to the supplementary materials, the moisture content of ginseng (75.34%), crude protein 2.78%, crude fat 0.53%, ash 0.018%, respectively. Consomm$\acute{e}$ soup beef cone with the addition of solid content and viscosity measurements, the results showed BCG0 3.34% viscosity ginseng 0% 2.26 acid group most were lower. The sweetness of the control group, 0% added ginseng lowest measured pH is 6.53, and 4.13 BCG12 the lowest amount was measured. Consomm$\acute{e}$ soup beef cone with the addition of lightness was lower as the control group BCG0 34.21, redness BCG0 14.44 as the highest value, respectively. Yellowness decreased significantly (p<0.001) between the amount of ginseng have more and more each sample. Turbidity was decreased with increasing the amount of ginseng. Ginseng added 6% BCG6 symbols from color BCG9 5.10 the highest rating, and flavor 5.40 as the highest rating was 9% added BCG9 5.70 overall acceptability overall acceptance was rated the highest. Strength ginseng 0% added in the control group showed the highest intensity of 6.4, dark brown. Savory flavor 0% added ginseng BCG0 showed the lowest intensity to 4.4. Consomm$\acute{e}$ soup when you try to synthesize the results of all the experiments, the addition of ginseng considered the best addition to the 9%, and the addition of more than 12% of ginseng reducing rather symbols that suggest.

• Journal of The Korean Association For Science Education
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• v.15 no.3
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• pp.250-262
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• 1995

Investigation on the appendices was carried out to acquire teaching materials about improvement of a appendices and development of teaching-learning activities for science textbooks in Korean middle schools. We analysed the appendices for 30 kinds of science textbooks used in Korean middle schools during $1969{\sim}1994$ years. In the results there were three kinds of pattern for the appendices, such as appendix, non-appendix, and similar appendix without appendix title. The content of appendices were summarized as six categories. such as list of science and scientist history, SI unit-constants and symbols, handling methods of instruments for basic experiments, measuring methods and inquiry activity, safety and precautions, and supplementary data with figures and tables. The appendices of six categories were mostly a content of general and integrated science, and were concentrated in the first grader's textbooks. There were many appendices about the methods for basic experiments such as 'How to Use of Experimental Appliances' in the first grader's science textbooks, but there was no or lack of them in the second and the third grader's science textbooks in the middle school. By the ratio to the pages of appendices which were included according to curriculum changes. the ratio was found to be 4.47% which was the highest in middle school science textbooks at the second curriculum and to be 3.47% which was the highest in high school biology textbooks at the second curriculum. The results of this study indicated that the science textbooks should include as many appendices as possible, because teachers could utilize them in teaching activities and students should be able to be given much help in self-learning.

• Journal of Korean Library and Information Science Society
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• v.48 no.4
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• pp.429-448
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• 2017

The purpose of this study is to present the development direction of future reading education by examining the characteristics of reading materials within the high school textbook developed as the 2015 revised curriculum. For this purpose, reading materials of high school textbooks were analyzed in Korean language, mathematics, English, integrated science, and integrated social studies. The analysis criteria of reading materials were subject type, purpose, and student activities. As a result of the study, reading materials on various themes such as humanity, liberty, culture, environment, and district were presented in the integrated society and integrated science textbook of the 2015 revised curriculum. In particular, the Korean language curriculum was composed of a unit called "reading one book in one semester". However, most reading materials have no guidance on reading effective or reading direction, and lack of reading materials and information for extended reading. The reader's reading of the textbook was found to be simply supplementing the learning content of each unit or presenting fragmentary cues for conceptual purposes. This suggests that there is a lack of awareness of students' interest in reading, internalization of reading, and extension of reading. In this paper, we suggest supplementary materials of reading materials for expanding the high school textbooks, and explore the developmental relationship between textbooks and reading education through suggestions on aspects of textbook composition and teaching methods.

• Computers and Concrete
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• v.22 no.4
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• pp.407-417
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• 2018

Over the past three decades, self-compacting concrete (SCC), which is characterized by its superior rheological properties, has been gradually used in construction industry. It is now recognized that the application of SCC using supplementary cementitious materials (SCM) is highly attractive and promising technology reducing the environmental impact of the construction industry and reducing the higher materials costs. This paper presents an experimental study that investigated the mechanical and durability properties of SCCs manufactured with blended binders including fly ash, slag, and micro-silica. A total of 8 batches of SCCs were manufactured. As series of tests were conducted to establish the rheological properties, compressive strength, and durability properties including the water absorption, water permeability, rapid chloride permeability and initial surface absorption of the SCCs. The influences of the SCC strength grade, blended types and content on the properties of the SCCs are investigated. Unified reactive indices are proposed based on the mix proportion and the chemical composition of the corresponding binders are used to assess the compressive strength and strength development of the SCCs. The results also indicate the differences in the underlying mechanisms to drive the durability properties of the SCC at the different strength grades.

• Computers and Concrete
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• v.31 no.2
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• pp.111-121
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• 2023

The influence of material composition such as aggregate types, addition of supplementary cementitious materials as well as exposed temperature levels have significant impacts on concrete residual mechanical strength properties when exposed to elevated temperature. This study is based on data obtained from literature for fly ash blended concrete produced with natural and recycled concrete aggregates to efficiently develop prediction models for estimating its residual compressive strength after exposure to high temperatures. To achieve this, an extensive database that contains different mix proportions of fly ash blended concrete was gathered from published articles. The specific design variables considered were percentage replacement level of Recycled Concrete Aggregate (RCA) in the mix, fly ash content (FA), Water to Binder Ratio (W/B), and exposed Temperature level. Thereafter, a simplified mathematical equation for the prediction of concrete's residual compressive strength using Gene Expression Programming (GEP) was developed. The relative importance of each variable on the model outputs was also determined through global sensitivity analysis. The GEP model performance was validated using different statistical fitness formulas including R², MSE, RMSE, RAE, and MAE in which high R² values above 0.9 are obtained in both the training and validation phase. The low measured errors (e.g., mean square error and mean absolute error are in the range of 0.0160 - 0.0327 and 0.0912 - 0.1281 MPa, respectively) in the developed model also indicate high efficiency and accuracy of the model in predicting the residual compressive strength of fly ash blended concrete exposed to elevated temperatures.

• Advances in nano research
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• v.15 no.5
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• pp.467-484
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• 2023

Despite the significant features of fiber-reinforced cementitious composites (FRCCs), including better mechanical, fractural, and durability performance, their high content of cement has restricted their use in the construction industry. Although ground granulated blast furnace slag (GGBFS) is considered the main supplementary cementitious material, its slow pozzolanic reaction stands against its application. The addition of nano-sized mineral modifiers, including nano-silica (NS), is an alternative to address the drawbacks of using GGBFS. The main object of this empirical and numerical research is to examine the effect of NS on the strain-hardening behavior of cementitious composites; ten mixes were designed, and five levels of NS were considered. This study proposes a new method, using a four-point bending test to assess the use of nano-silica (NS) on the flexural behavior, first cracking strength, fracture energy, and micromechanical parameters including interfacial friction bond strength and maximum bridging stress. Digital image correlation (DIC) was used for monitoring the initiation and propagation of the cracks. In addition, to attain a deep comprehension of fiber/matrix interaction, scanning electron microscope (SEM) analysis was used. It was discovered that using nano-silica (NS) in cementitious materials results in an enhancement in the matrix toughness, which prevents multiple cracking and, therefore, strain-hardening. In addition, adding NS enhanced the interfacial transition zone between matrix and fiber, leading to a higher interfacial friction bond strength, which helps multiple cracking in the composite due to the hydrophobic nature of polypropylene (PP) fibers. The findings of this research provide insight into finding the optimum percent of NS in which both ductility and high tensile strength of the composites would be satisfied. As a concluding remark, a new criterion is proposed, showing that the optimum value of nano-silica is 2%. The findings and proposed method of this study can facilitate the design and utilization of green cementitious composites in structures.

• Journal of the Korea Concrete Institute
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• v.26 no.1
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• pp.13-21
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• 2014

To quantitatively evaluate the influence of ground granulated blast-furnace slag (GGBS) as a supplementary cementitious material on the life-cycle environmental impact of concrete, a comprehensive database including 3395 laboratory mixes and 1263 plant mixes was analyzed. The life-cycle assesment studied for the environmental impact of concrete can be summarized as follows: 1) the system boundary considered was from cradle to pre-construction; 2) Korea life-cycle inventories were primarily used to assess the environmental loads in each phase of materials, transportation and production of concrete; and 3) the environmental loads were quantitatively converted into environmental impact indicators through categorization, characterization, normalization and weighting process. The life-cycle environmental impacts of concrete could be classified into three categories including global warming, photochemical oxidant creation and abiotic resource depletion. Furthermore, these environmental impacts of concrete was significantly governed by the unit content of ordinary portland cement (OPC) and decreased with the increase of the replacement level of GGBS. As a result, simple equations to assess the environmental impact indicators could be formulated as a function of the unit content of binder and replacement level of GGBS.