• Title/Summary/Keyword: River sand

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The use of river sand for fine aggregate in UHPC and the effect of its particle size

  • Kang, Su-Tae
    • Advances in concrete construction
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    • v.10 no.5
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    • pp.431-441
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    • 2020
  • For the purpose of improving the properties of UHPC as well as the economic efficiency in production of the material, Availability of river sands as fine aggregate instead of micro silica sand were investigated. Four different sizes of river sands were considered. Using river sand instead of micro silica sand increased the flowability, and decreased the yield stress and plastic viscosity in rheological properties, and the effect was higher with larger particle size of river sand. It was demonstrated by analyses based on the packing density. In the results of compressive strength and elastic modulus, even though river sand was not as good as micro silica sand, it could provide high strength of over 170 MPa and elastic modulus greater than 40 GPa. The difference in compressive strength depending on the size of river sand was explained with the concept of maximum paste thickness based on the packing density of aggregate. The flexural performance with river sand also presented relatively lower resistance than micro silica sand, and the reduction was greater with larger particle size of river sand. The flexural performance was proven to be also influenced by the difference in the fiber orientation distribution due to the size of river sand.

EFFECTS OF RIVER DISCHARGE ON GROWTH OF PERIPHYTON IN SAND RIVER

  • Toda Yuji;Tsujimoto Tetsuro;Fujimori Noriomi
    • Water Engineering Research
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    • v.6 no.3
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    • pp.113-122
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    • 2005
  • Periphyton is known to be one of major primary producers for river ecosystem. While the growth of periphyton usually observed on the stone surface in gravel river, the large growth of periphyton is sometimes seen even in sand river with relatively small river discharge. In the present study, field observations and numerical simulations were performed to investigate the growth of periphyton in sand river. In the field observation, the growth of periphyton on fixed sand bed was measured weekly. The results of the field observations show that the large growth of periphyton occurs in sand river until the bed material sands have not moved. An integrated numerical simulation model is presented to describe the growth of periphyton at observed river reach, and a series of numerical simulations were performed to study the effect of river discharge on growth of periphyton in the sand river. The results of the numerical simulations show that the net primary production of periphyton decreases with the river discharge. These results suggest that the reduction of river discharge at ordinary water stage strongly affects the primary productivity of periphyton even in sand river.

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Study on Hydraulic Effect from Removal of Sandbar in River (하천 사주의 제거로 인한 수리적 영향에 관한 연구)

  • 천만복
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.39 no.1
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    • pp.48-53
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    • 1997
  • The sand bar has developed at the junction of the Kum-ho River and Shin-ryoung River. The sediment transported from the Kumho River basin has decreased since the Youngchon Dam has been functioning. Sand bar and the vicinity of the bottleneck at the upstrem of Kumho River and Osu Island which is consisted of sand bar have inundated frequently. This study was carried out through the hydraulic model test to calibrate the hydraulic effect from removal of sand bar in the river and straightening the river course by land reclamation. The water level of river at the vicinity of bottleneck can be lowered as much as 0.40~0.7m when the sand bar is removed. When river is straightened the river course by land reclamation the water level can be lowered as half of removal of sand bar.

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A Study on the Properties of Cement Mortar Using Blended Sand (혼합모래를 사용한 시멘트 모르터의 특성에 관한 연구)

  • Park Yong-Kyu;Kim Min-Ho;Yoon Gi-Won;Ryu Hyun-Gi;Han Cheon-Goo
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2005.05a
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    • pp.65-68
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    • 2005
  • This paper investigated the engineering properties of cement mortar mixed with more than 2 kinds of sand. For fresh mortar properties, unit volume weight is constant regardless of mixing content and type of sand. An increase in contents of river and crushed sand resulted in an increase in flow, whereas an increase in recycled sand contents reduced flow. Gap between maximum flow in N3C0R0 and minimum flow in N0C0R3 exhibited about $12\%$. Compressive strength at 28 days ranged from 32 to 36 MPa in order for crushed sand, river sand and recycled sand. Mortar with mixed sand along with river sand and crushed sand showed compressive strength comparable to crushed sand. An increase of fraction of recycled sand in mixed sand resulted in a decrease in compressive strength. For drying shrinkage, N0C0R3 had the largest drying shrinkage among various mixture type. The combination of large contents of recycled sand and small contents of river and crushed sand had a large amount of drying shrinkage.

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Roughness and Shape Analysis on Granular Materials (조립토의 거칠기 및 모양 분석)

  • 민덕기;이완진;이종익
    • Proceedings of the Korean Geotechical Society Conference
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    • 2002.10a
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    • pp.245-252
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    • 2002
  • The roughness of Joomoonjin sand and the Dongchun river sand was analysed by the fractal theory. It was found that the fractal dimension(D$\_$F/) of Joomoonjin sand is a little smaller than the Dongchun river sand. That means Joomoonjin sand is smoother than the Dongchun river sand. The measurements of D$\_$F/ of different fraction of the Donchun river sand showed that large particles were rougher than fine particles. The shapes of both sands were analysed by the Discrete Fourier Transform(DFT) and the Grid-based(GB) method. Normalization of coefficients with respect to size, starting point and its orientation made the coefficients invaried to these characteristics. The mean of the normalized coefficients was used to reconstruct the average shape for both sands, respectively. The measurements of the ellipticity ratio of different fraction of both sands showed that Joomoonjin sand is slightly flatter than the Dongcun river sand.

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Study on the Properties of Antiwashout Underwater Concrete with Variation of Blend Ratio of Crushed Sand (부순모래 혼입률 변화에 따른 수중불분리성 콘크리트의 특성 연구)

  • 박세인;오광영;이환우;김종수;김명식
    • Proceedings of the Korea Concrete Institute Conference
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    • 2001.11a
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    • pp.427-432
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    • 2001
  • In this study, crushed sand is blended with river sand and sea sand, to investigate the quality change of antiwashout underwater concrete with variation of blend ratio of crushed sand(0%, 20%, 40%, 60%, 80%, 100%). To see experiment conclusion, the more blend ratio of crushed sand increases, the more unit weight increases. Because the for that specific gravity of crushed sand is higher comparatively than that of river sand and sea sand. Higher compressive strength is measured following the order of river sand, crushed sand, sea sand regardless of age and casting-curing condition. Except for case of using river sand, blend ratio of 40% is appeared on most compressive strength. So the optimum blend ratio of crushed sand is 40% from the view point of compressive strength.

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Study on the Properties of Antiwashout Underwater Concrete with Variation of Mixing Proportion of Fine Aggregate Types (잔골재의 혼합비율 변화에 따른 수중불분리성 콘크리트의 특성에 관한 연구)

  • 배원만;박세윤;백동일;김명식
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.11a
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    • pp.533-536
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    • 2003
  • The objective of in this study makes investigation into the characteristics of antiwashout underwater concrete as to mix proportion, casting and curing water through experimental researches. in this study, sea sand is blended with river sand, crushed sand is blended with river sand and sea sand as to investigate the quality change and characteristics of antiwashout underwater concrete with variation of blend ratio of sea sand and crushed sand(0, 20, 40, 60, 80, 100%). Higher compressive strength is measured following the order of river sand, sea sand, crushed sand regardless of age and casting condition. Except for case of using river sand, blended ratio of 40% is appeared on most compressive strength.

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Drying Shrinkage and Durability of Concrete Using Fine River Sand (하천세사를 사용한 콘크리트의 건조수축 및 내구성)

  • Bae, Suho;Jeon, Juntai;Kwon, Soonoh
    • Journal of the Society of Disaster Information
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    • v.9 no.4
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    • pp.493-502
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    • 2013
  • The purpose of this research is to estimate the drying shrinkage and durability of concrete using the fine river sand to utilize it actively as an alternative aggregate for concrete. For this purpose, the fine river sand samples were collected at the mid and down stream of main stream of Nakdong-River, and then the concrete specimens using the fine river sand were made according to strength level. After obtaining relation equation between compressive strength and cement-water ratio from the mix experiment result, the concrete specimens using different fine river sand were made for the specified concrete strength of 35MPa, and then their drying shrinkage and durability such as the resistance to freeze and thaw and carbonation were evaluated. It was observed from the test result that the durability of concrete using fine river sand was similar to that of concrete using reference sand, but the drying shrinkage of concrete using the fine river sand with small fineness was comparatively larger than that of concrete using reference sand.

The Properties of Inter-Locking Block with the Variation of Particle Grading and Shape of Aggregate (골재의 입도와 입형 변화에 따른 인터로킹 블록의 특성)

  • 이상태;김기철;신병철;김진선;권상준;한천구
    • Proceedings of the Korea Concrete Institute Conference
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    • 1998.04b
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    • pp.661-664
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    • 1998
  • In this paper, the properties of inter-lacking block by the kind of aggregate and fineness modulus are investigated. According to the experimental results, compressive strength and flexural strength increase and absorption ratio decrease with larger fineness modulus in the range of 2.15~4.20. Flexural strength with river sand is higher than that with crushed sand by about 19%, compressive strength with river sand, that with crushed sand by about 11% and absorption ratio with river sand is smaller than that with crushed sand by abort 2%.

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A Study on the Material Properties of Concrete Using Crushed Sand (부순모래를 사용한 콘크리트의 물성에 관한 연구)

  • 윤용호;정용욱;이승한
    • Proceedings of the Korea Concrete Institute Conference
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    • 2003.11a
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    • pp.106-111
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    • 2003
  • This paper is to investigate the characteristics of a concrete in which river sand is partially substituted with crushed sand. Since river sand has a relatively small fineness modulus, there is a need to increase the fineness modulus of sand used in the manufacture of concrete. In an experiment, it was observed that when river sand had a fineness modulus of 2.0~2.4 and crushed sand had a fineness modulus of 2.8~3.5, the substitution rate of the crushed sand was preferably within the range of 25~50%. The experimental results also revealed that as the substitution rate of the crushed sand increased, the flowability of the concrete tended to increase. However, when the substitution rate of the crushed sand reached 75% or more, the workability of the concrete was considerably poor. Further, as the substitution rate of the crushed sand increased, the air content and the bleeding rate of the concrete were low.

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