• Advances in concrete construction
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• 제5권2호
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• pp.173-182
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• 2017

This paper is aimed at determining the shear and impact strength of waste plastic fibre reinforced concrete. M30 grade of concrete is prepared with waste plastic door fibres cut into 5 mm width and aspect ratios of 30, 50, 70, 90 and 110. Fibres are used in a volume fraction of 0 to 1.5% with an increment of 0.25%. L shaped specimens are cast for shear strength tests and flat plates of size $250{\times}250{\times}30mm$ are used for impact tests. "Drop ball method" is used for checking the impact strength. Shear strength is checked with L shaped specimens under UTM with a special attachment. It was found that up to 1.25% of waste plastic fibres can be effectively used for better strength of concrete both in shear and impact. Shear and impact strength were found to be increasing up to a volume fraction of fibres of 1.25%.

• Advances in concrete construction
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• 제1권4호
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• pp.305-318
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• 2013

Engineering properties such as compressive strength, splitting tensile strength, modulus of rupture, modulus of elasticity and Poisson's ratio of geopolymer concrete (GPC) and steel fibre reinforced geopolymer concrete (SFRGPC) have been obtained from standard tests and compared. A total of 15 specimens were tested for determining each property. The grade of concrete used was M 40. The percentages of steel fibres considered include 0.25%, 0.5%, 0.75% and 1%. In general, the addition of fibres improved the mechanical properties of both GPC and SFRGPC. However the increase was found to be nominal in the case of compressive strength (8.51%), significant in the case of splitting tensile strength (61.63%), modulus of rupture (24%), modulus of elasticity (64.92%) and Poisson's ratio (50%) at 1% volume fraction of fibres. An attempt was made to obtain the relation between the various engineering properties with the percentage of fibres added.

• Structural Engineering and Mechanics
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• 제63권2호
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• pp.217-223
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• 2017

Glass fiber reinforced gypsum panels (GFRG) are hollow panels made from modified gypsum plaster and reinforced with chopped glass fibers. The hollow cores of panels can be filled with in-situ concrete/reinforced concrete or insulation material to increase the structural strength or the thermal insulation, respectively. GFRG panels are unfilled when used as partition walls. As load bearing walls, the panels are filled with M 20 grade concrete (reinforced concrete filling) in order to resist the gravity and lateral loads. The study was conducted in two stages: First stage involves formulation of the alternate light weight mix by conducting experimental investigations to obtain the optimum combination of phosphogypsum and shredded thermocol. In the second stage the alternate mixes are filled in GFRG panels and experimental investigations are conducted to compare the performance against panels filled with conventional M 20 mix.

• Steel and Composite Structures
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• 제4권2호
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• pp.95-112
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• 2004

A series of tests was performed to consider the behaviour of short composite columns under axial compressive loading, covering a range of S275 and S355 grade steel square hollow section filled with normal and high strength concrete. The interaction between the steel and the concrete component is considered and the results show that concrete shrinkage has an effect on the axial strength of the column. Comparisons between Eurocode 4, ACI-318 and the Australian Standards with the findings of this research were made. Result showed the equation used by the ACI-318 and the proposed Australian Standards gave better predication for the axial capacity of concrete filled SHS columns than the Eurocode 4.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.489-492
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• 2006

Needs for the new technologies and cutting-edge Ultra Flowing Self-Compacting Concrete are emerging as the concrete structures are becoming bigger and more specialized recently. In North America and Europe, SCC, which has high resistance against flow ability and segregation, is being used as concrete material in applications such as precast and prestressed bridges, where reinforcing bars are overcrowdedly placed. In Korea, SCC has been utilized limitedly in building structures but its utilization should be expanded to engineering structures such as bridges. In this study, for the application in precast and prestressed bridges with overlycrowded reinforcing bars, USCC was mixed with admixtures to give a binary system and a ternary system according to the 1st grade rules by JSCE (Japan Society of Civil Engineers). Compressive strength and splitting tensile strength of the resulting USCCs were tested. Elastic modulus were compared with the values suggested in CEB-FIP code and ACI 318-05.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.801-804
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• 2006

Polycarboxylate type superplasticizers(PC) have got widely used for making not only high performance concrete but low grade concrete as well. It is known that fluidity of cement with PC is affected by the characteristics of cement especially sulphate ion concentration and hydration activity. But the characteristics of PC also affect the fluidity. The fluidity of cement mortar with various types of PC was measured and critical dosage(CD) and dispersing ability(DA) was calculated. CD and DA is strongly dependent on the type of PC. And the variation of fluidity on time was affected by the type of PC also. So, it is advisable to investigate the property of PC before production of concrete and adjust it to meet the requirements of concrete depending on the materials, the time of transport and so on.

• 한국구조물진단유지관리공학회 논문집
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• 제3권2호
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• pp.155-160
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• 1999

Recently, the study on mix design of lightweight concrete using the polystyrene foam balls is put into practice from the viewpoint to grade up the quality of concrete and recyclable usage of industrial by products. Polystyrene aggregate concrete, PAC, can be used as structural concrete in low strength application. For instance, PAC could be used in the middle part of sandwich panel where stresses are generally low and in the case of grid-type reinforcement where it does not need high bond strength but little compressive strength to resist the pressure of transverse reinforcement. From this point of view, the authors discussed the influence of fluidity and compressive strength of concrete by the difference of the volume percentage of polystyrene foam balls and water cement ratio.

• Advances in concrete construction
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• 제5권1호
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• pp.75-86
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• 2017

An experimental work was carried out to study the effect of hybrid fiber on the tension stiffening and cracking characteristics of geopolymer concrete (GPC). A total of 24 concentrically reinforced concrete specimens were cast and tested under uniaxial tension. The grade of concrete considered was M40. The variables mainly consist of the volume fraction of crimped steel fibers (0.5 and 1.0%) and basalt fibers (0.1, 0.2 and 0.3%). The load deformation response was recorded using LVDT's. At all the stages of loading after the first cracking, crack width and crack spacing were measured. The addition of fibers in hybrid form significantly improved the tension stiffening effect. In this study, the combination of 0.5% steel fiber and 0.2% basalt fiber gave a better comparison than the other combinations.

• 한국과학교육학회지
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• 제4권2호
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• pp.64-73
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• 1984

This study aimed at identifying the characteristics of current science curriculum in several countries in terms of its format, aims and objectives, contents and guidelines and discussed about therm. The curricula were collected from 9 countries- The United States of America(5 states), Canada(4 Provinces), England, West Germany, France, Australia, Newzealand, Japan and the republic of China. Each country had her own characteristics of science curriculum, but there also common characteristics among several countries. First, the format of science curricula in eastern countries were very different from those of western countries. The western countries had the curriculum format which included characteristics and needs of science education, philosophy and background, aims and objectives, contents, characteristics of learners, teaching and learning strategy, teaching materials, guide of experiments, evaluation methods, and other concrete informations while eastern countries had the curriculum format which included only objectives, contents and guidelines. I think that the format of science curriculum in western countries is more recommendable than that of eastern countries. Second, the aims and objectives of science curricula in eastern countries focused on scientific knowledges and concepts, while those of countries emphasized scientific methods and attitudes. Third, the contents of science curricula were very similar regardless of eastern countries or western countries. In other words, all the countries in this study emphasized life science and earth science at lower grade level and physical science at upper grade level. Especially the observation and concrete learning activities were suggested at lower grade level and logical reasoning was emphasized at upper grade level. I think that the integrated (topic-centered) science curriculum is more recommendable than our current non-integrated science curriculum in lower grade levels. Finally, the guidelines of science curriculum in eastern countries did not suggest specific information about teaching contents, experimental methods, teaching-learning activities, evaluation methods, teaching and learning meterals, while those of western countries provided more specific information which teachers could utilize very effectively.

• 한국과학교육학회지
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• 제5권1호
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• pp.1-9
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• 1985

It is apparent to anyone who has taught science in secondary. schools that a substantial percentage of students find the subject difficult: What is the cause of difficulty? There is season to believe that part of this difficulty is associated with students' intellectual development as deserifed by Piaget. To investigate the difficulty students face with learning science in the light of Piagetian developmental theory, the stages of the intellectual development of the secondary school student s were assessed in this study using the instrument called Group Assessment of Logical Think ing (GALT). The results of this study showed that more than 60% of 7th and 8th grade students were Classified as concrete operational level. It was also found that only 20% of the students from 9th through 11th grade were formal operational stage, while about 40% of them were still at concrete operational stage. This study showed that. there was a significant main effect on the intellectual development of the students by grade. However, it showed that at 0.5 level of significance there was no main effect by sex although mean scores of male on the assessment were higher than those of female.