• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.6
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• pp.178-184
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• 2017

This study was aimed to investigate the tensile behaviors of PE(Polyethylene) fiber-reinforced highly ductile cementitious composites with different combinations of micro silica sand and normal sand(river sand) with maximum particle size of 4.75 mm. Flow test result indicated the increase of flowability with higher replacement ratio of river sand. There was no noticeable difference in the mean compressive strength with different replacement ratio of river sand, but the variation in the compressive strength increased as higher amount of river sand was adopted for the replacement. The difference in the uniaxial tensile strength was negligible, but the tensile strain capacity was significantly influenced by the replacement ratio of river sand. It is thought that increased density of multiple cracks induced improved tensile strain capacity when higher percentage of river sand was adopted for fine aggregate. The deviation in the strain capacity increased as the replacement ratio of river sand was higher, as in the compressive strength. This study presented the feasibility of using normal sand instead of micro silica sand for highly ductile cementitious composites with equivalent or better uniaxial tensile performance, even though it might increase the deviation in the performance.

• Journal of The Geomorphological Association of Korea
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• v.18 no.2
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• pp.53-63
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• 2011

The changes and causes of channel section in Naeseongcheon River, a tributary of Nakdong River, during the long(1984~2001) and short(2009~2011) periods are analyzed. There are the declines of channel height with a maximum of approximately 2m in the most areas of the lower reaches during the past 20 years. These are thought as the influences of active aggregate collections and river dredging. The size of sand bar within the channel at the NM1 decreases greatly during the past 2 years. This may results from the decrease of sediment supply due to the Yeongju Dam construction in the upper reaches. However, the NM2 and NL2 where the natural channel are preserved experience the slight increase of height during the past 2 years. Therefore, the anthropogenic channel interferences in Naeseongcheon River have greatly influenced on the declines of channel height by the decrease of sediment supply.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.04a
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• pp.142-147
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• 1994

Lately, among concrete component used in construction works, the aggregate is the most important material because it hold about 70~80 Vo1% of most structural materials. Considering that the demand of aggregate is on the continuous increase in the construction works year after year, it is a very urgent thing to develop a substitute aggregate for river aggregate. This paper, an experimental study on the effect of corrosion protection by tighting concrete used fly-ash and silica fume, is to investigate workability and engineering properties of concrete used fly-ash and silica fume. As a test results, contrary to SF, workability of concrete used FA is inclined to be improved. And in the case of containing SF, the compressive strength containing admixtures is higher than plain concrete with increasing curing age.

• Proceedings of the Korea Concrete Institute Conference
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• 1990.04a
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• pp.24-28
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• 1990

The purpose of this study is to examine through the experimental study whether the water cooled unprocessed blast furnace slag produced in the country is useful for the fine aggregate of concrete or not. The results of this study show that the quality of the water cooled blast furnace slag is inferior to that of natural river sand and that the concrete made by substituting the water cooled blast furnace slag for fine aggregate have a tendency to decrease to some extent in strength. But if the water cooled blast furnace slag is transformed into more hardened state material, to use it as the fine aggregate of concrete will be possible.

• Journal of The Korean Society of Agricultural Engineers
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• v.48 no.7
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• pp.25-31
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• 2006

Permeable polymer concretes can be applied to roads, sidewalks, river embankment, drain pipes, conduits, retaining walls, yards, parking lots, plazas, interlocking blocks, etc. This study was to explore a possibility of using bottom ash as filler and recycled coarse aggregate of industrial by-products for permeable polymer concrete. The tests carried out at $20{\pm}1^{\circ}C$ and $60{\pm}2%$ relative humidity. At 7 days of curing, unit weight, void ratio, compressive and flexural strength and coefficient of permeability ranged between $1,652{\sim}1,828kgf/m^{3},\;15{\sim}29+%,\;18.2{\sim}24.5\;MPa,\;6.4{\sim}8.4\;MPa\;and\;6.8{\times}10^{-2}{\sim}1.7{\times}10^{-1}\;cm/s$, respectively. It was concluded that the bottom ash and recycled coarse .aggregate can be used in the permeable polymer concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.271-275
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• 1998

Recently, in the trend of using aggregate, it is common that coarse aggregate is replaced with crushed stone and fine aggregate is replaced with sea sand as a replacing aggregate. In this study, to judge the adaptability of using antiwashout underwater concrete, we used mixed sand (river sand : sea sand= 5 : 5) and changed W/C. After carrying out the research on the strength development of the compressive strength of specimen, tensile strength, fluxural strength which is produced and cured in the air and salt water, we founded that when W/C was low and the amount of AWA and SP were increased, the state of strength development was excellent.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.453-456
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• 2005

The use of lightweight concrete products is usually increased at a recently high structures. Among the rest EPSB concrete products which have an excellence on the sound and thermal insolation are used. Also, the gathering of nature aggregate is limited, so that lack of fine aggregate is appearing. The purpose of this study is to obtain basic data of properties of EPSB concrete in according to types of aggregate. The results of experiment are as follow. The EPSB concrete using bottom ash is appeared the lowest slump in fresh concrete. The EPSB concrete using river sand and bottom ash are showed as a similar compressive strength except it using crushed sand in hardened concrete.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2019.11a
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• pp.83-84
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• 2019

Recently, the supply and demand of aggregates has become difficult due to various practical constraints such as depletion of natural aggregate resources and tightening environmental regulations. As a result, aggregates such as selective crushed aggregates and river aggregates are now distributed to the construction market. In particular, among the aggregates distributed in the country, selective crushed aggregates that have been used recently are characterized by the fact that the quality of the raw material is not uniform and is based on geological characteristics. Such bad aggregates can affect the overall performance of the concrete and shorten the life of the structure. Therefore, in this study, in order to improve such problems, we want to analyze the effect of aggregate powder on mortar.

• Proceedings of the Korean Institute of Building Construction Conference
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• v.y2004m10
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• pp.55-58
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• 2004

This paper investigated the results of quality of concrete using mixed sand with grading adjustment in order to find out the applicability of fine aggregate with bad grading, According to test results, fluidity of concrete with fine level grading river sand was decreased while with coarse level grading crushed sand increased compared with that with medium level grading crushed sand. Use of mixed sand with grading adjustment(MSG) resulted in an improvement in fluidity. Increase in fineness modulus led to an increase in bleeding, For compressive strength, use of MSG increased compressive strength. For drying shrinkage, use of fine level grading river sand resulted in an increasing drying shrinkage due to the larger presence of fine particles, while use of MSG led to a reduction in drying shrinkage

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.05a
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• pp.107-110
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• 2006

In this study, recently it is urgently required that recycle promotion of construction and demolition waste concrete because urban development is accelerated and redevelopment project is rapidly expanded, production quantity of construction and demolition waste concrete is being increased. On the other hand, it is urgently required that problem solution of demand and supply unbalance of fine aggregate because the sea sand is restricted by exhaustion of river sand and intensification of environment influence evaluation. Therefore, it tries to conform in time necessity, there is the objective of this study to provide the fundamental data about the re-application as the comparison and analysis the quality present condition for the recycled fine aggregate in the inside and outside of the country. At the same time it will be able to improve the quality of the recycled fine aggregate waste as investigating the physical nature and a quality present condition of the recycled fine aggregate from construction waste.