• 한국항만학회지
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• 제9권1호
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• pp.65-72
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• 1995

This study is being done for the purpose to achieve a stable demand and supply of materials for long term. The author investigated condition of suitable mixer design method for concrete, an individual value and a character of dynamics as a supplement material by drying up the natural aggregate, and a possible practicalization plan to reduce defects to the minimum. As a result of this study, it can be acquired a good quality of concrete by the use of the natural sand (Nak Dong river sand) and the crushed sand with suitable mixing ratio. The fineness modulus (F.M) of mixing aggregate is $2.7\pm1$ at this time and this is good for workbility and plasticity of concrete.

• 자원환경지질
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• 제57권3호
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• pp.293-303
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• 2024

River mining, the extraction of sand and gravel from riverbeds, is rising at an alarming rate to keep pace with the increasing demand for construction materials worldwide. The far-reaching deleterious effects of river mining include the lowering of water levels, the augmentation of turbidity, and the erosion of riverbanks, i.e., the disruption of water flow and alteration of river morphology. Aggregates demand, geolocation, and the economy of Bangladesh accelerated illegal extraction. However, limited research has been carried out in this region, despite the severe impact on aquatic and terrestrial ecosystems. To address the corresponding consequences and direct the scope for further research, it is required to evaluate existing studies of other countries having similarities in river morphology, climate, economy, and other related parameters. In this respect, based on previous studies, the effects of sand extraction are particularly prominent in India, having 54 cross-boundary rivers with Bangladesh. The geological profile of numerous rivers in the past decades has been altered due to natural aggregate mining in the Indian subcontinent. Hence, this study focused on relevant research in this region. However, the existing research only focuses on the regional portion of the aforementioned international rivers, which lacks proper assessments of these rivers, taking into account especially the mining effects. Moreover, several global rivers that have similarities with Bangladeshi rivers, considering different parameters, are also included in this study. The findings of this article underline the pressing need for more efficacious measures to address the adverse effects of river mining and safeguard ecosystems and communities globally, especially in the Indian subcontinent, where the situation is particularly vulnerable. For this reason, targeting the aforementioned region, this review highlights the global evidence in assessing the future effects of river mining and the need for further research in this field.

• Computers and Concrete
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• 제19권6호
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• pp.617-623
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• 2017

This work is conducted with the aim of using waste material to reserve the natural resources. The objective is accomplished by conducting experimentation and verify by modeling based on fuzzy logic. In experimentation, concrete is casted by using natural/river sand as fine aggregate and termed as control specimen. Natural sand is conserved by replacing it with used foundry sand (UFS) by an amount of 10, 20 and 30% by weight. Fresh and hardened properties of concrete are investigated at different ages. It is observed that compressive strength and modulus of elasticity reduced with the increase in amount of UFS. Furthermore, concrete compressive strength is predicted by using fuzzy logic model and verified at different replacement ratio and age with experimental observations.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1993년도 봄 학술발표회 논문집
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• pp.40-45
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• 1993

Due to the recent shortage of river sand resulting from a rapid growth of concrete construction, sea sand and pit sand are increasingly used in stead. It is , however, well noted that non-washed sea sand used in reinforced concrete causes to corrode reinforcing steel and to incur cracks in concrete, and thus eventually result in damage to concrete. Moreover, many sources of pit sand in our country are randomly used without experimental research for its applicability to concrete construction. The purpose of this research to activate the usage of pit sand and sea sand for concrete construction to solve the recent shortage of river sand. Followings have been experimentally investigated : 1)Physical properties of pit sand and sea sand, 2)Compressive strength of mortar on the weight of pit sand passing through No.200 sieve, 3) Compressive strength of mortar on the chloride content of sea sand, 4) Compressive strengths of concrete using pit sand and sea sand, respectively, 5)Corrosion propagatio in reinforcing steel on the chloride concent, of sea sand, and 6)etc.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.317-322
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• 2001

This paper investigates the influence of fine aggregates on bleeding of concrete. According to test results, as water content decreases, crushed sand content increases, fluidity shows decline tendency. As for aggregates kinds, concrete using sea sand shows most fluidity loss among the tested results. Compressive strength gains highly when crushed sand is used. As for bleeding of concrete, bleeding shows decline tendency because of increasing in powder content and filling effect of voids. Bleeding amount is in a decreasing order of magnitude for concretes made with the following aggregates: sea sand, river sand, and crushed sand. Accordingly, crushed sand mixed with river sand and sea sand with certain proportion enable to reduce bleeding and enhance strength.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.153-159
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• 1999

The objective of this study was to investigate the bond strength properties of antiwashout underwater concrete. The fine aggregate(river sand, blended sand (river sand : sea sand = 1 : 1), condition of cast and cure(sea water, fresh water), and compressive strength of proportion(210kgf/$\textrm{cm}^2$ ~ 330kgf/$\textrm{cm}^2$) were chosen as the experimental parameters. The experimental results show that the underwater segregation resistance was increased, but flowability (slump flow) and air contents were decreased as the compressive strength of proportion increased. Bond strength of antiwashout underwater concrete was similar to plain concrete. From this study, rational analytic formula for the modulus of rupture and bond stress are to be from compressive strength of concrete.

• 한국농공학회지
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• 제18권4호
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• pp.4265-4273
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• 1976

1. Fine aggregates of concrete are very important for the construction works and construction cost determination. Most of fine aggregates are from the river sand, but the amount of storage in the river side is steadily decreasing due to continuous construction works. Therefore, another source of fine aggregates is needed to meet increasied demand of sand. 2. Beach sand is a possible source of fine aggregates. But rust of steel bar is caused by CL-chemical of beach sand. Therefore, desalinization of beach sand is requested to get durable reinforced concrete. Economical methods of desalinization are as follows. (a) Flooding and drainage method. (b) Washing of beach sand with water supply and mixing. (c) Spreading of beach sand on the land and leaching by rain water for a few month. 3. Hardening of concrete with beach sand is accelerated due to salt, Thus early stage strength increase leads to make cracks. Also later stage strength decreases and durability becomes worse. By using appropriate admixture, the quality of concrete can be improved.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.237-240
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• 1999

This study was performed to analyze strength characteristics of concrete using FWS(foundry waste sand), as a way of study for reusing the FWS disused in the foundry as the fine aggregate for concrete. As the experimental results, the slump of concrete showed a decline with the increase of replacement ratio of FWS. The compressive strength of concrete made with FWS 25% replacement river sand showed higher value than that of concrete not containing FWS, but the flexural strength of concrete containing FWS was decreased 21% compared with that of concrete not containing FWS at age of 28days.

• 공업화학
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• 제23권4호
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• pp.409-415
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• 2012

폴리머 콘크리트 복합재료의 제조에 재활용하기 위하여 산업폐기물로 처리되고 있는 제강슬래그를 아토마이징 공법으로 구형의 골재를 제조하였다. 구형의 급냉 제강슬래그는 입도에 따라 폴리머 콘크리트 복합재료의 잔골재(강모래)와 굵은 골재(쇄석)를 대체하여 사용하였다. 급냉 제강슬래그를 사용하여 제조한 폴리머 콘크리트 복합재료의 제 물성을 조사하기 위하여 폴리머 결합재의 첨가율과 급냉 제강슬래그의 대체량에 따라 다양한 배합의 폴리머 콘크리트공시체를 제조하여 물성시험을 실시하였다. 시험결과, 급냉 제강슬래그를 적정량 대체하여 사용한 공시체의 기계적 강도가 현저히 향상되었으며(최대압축강도 117.1 MPa), 폴리머 콘크리트 복합재료의 생산원가에 가장 큰 영향을 미치는 폴리머 결합재의 사용량을 현저히 절감할 수 있었다. 그러나 폴리머 콘크리트 복합재료의 내열수성시험에서 공시체의 기계적 강도가 현저히 감소되었다.

• 한국건축시공학회지
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• 제21권6호
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• pp.551-562
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• 2021

본 연구에서는 IGCC에서 발생하는 부산물인 CGS를 콘크리트용 혼합 잔골재로써 효율적으로 활용하는 방안을 제시하기 위하여 플라이애시 치환 매스 콘크리트의 수화열 저감 효과를 확보하기 위한 방안으로 CGS 기반 혼합 잔골재와 플라이애시 치환에 따른 수화열 저감 특성 분석 및 해석을 실시 하고자 한다. 따라서, 매스 콘크리트의 수화열 저감을 위하여 활용되는 플라이애시 기반 저발열 결합재에 CGS를 잔골재로 치환하여 최적의 조합으로 FA 30% 및 CGS를 잔골재로 50% 치환할 경우 저발열 결합재 FA를 단일 치환한 경우보다 복합상승 효과에 따라 수화열 저감 성능이 더 크게 나타났다. 따라서 산업부산물인 CGS 골재 조합에 플라이애시를 복합 치환한 분체-골재조합 재료 시스템은 매스 콘크리트 수화열 저감 공법의 효율적인 대안으로서 활용이 기대된다.