• International Journal of Concrete Structures and Materials
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• 제3권1호
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• pp.11-14
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• 2009

This paper is interested in the incorporation of crushed sand and desert sand in the composition the self compacting concretes (SCC). Desert dune sand, which has a fine extra granulometry, and the crushed sand, which contains an important content of fines, can constitute interesting components for SCC. Part II consists in studying the behaviour of SCC containing various sands with different origins. These sands, with different sizes, consist of several combinations of rolled sand (RS), crushed sand (CS) and desert sand (DS). The study examines the influence of the granular combination of sands on the characteristics in the fresh and the hardened state of SCC. The results of the experimental tests showed an improvement of the workability of the fresh SCC by combining sands of varied granulometry. The addition of the DS to CS or to RS allowed the increase of the mixture viscosity but decreased the mechanical strengths. Furthermore, the CS-RS combinations increased the compressive and the tensile strengths of the studied SCC. The optimized formulations of sands gave the highest performances of the SCC.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2005년도 추계 학술논문 발표대회
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• pp.17-20
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• 2005

This study investigates mock-up test of the concrete containing crushed sands with improved quality and following could be draws as conclusions. The slump satisfies the target value. The air content reaches the goal, however, it decreases by the occurrence of loss with elagse of age. In normal strength region, the setting time of CS24 member is shorter than that of SS24 member. In high strength region, the setting time of SS50 member is make only slower than that of CS5O because of the use of retarding AE agent. The compressive strength of the concrete using crushed sands is little higher than the concrete using washed sea sands, and the compressive strength of core sample increases at lower part. Drying shrinkage of the concrete using crushed sands is larger than that using washed sea sands. At water caring condition, both the concrete using crushed sands and using washed sands expand at first, exhibit to be swelled and with elagse of age, they remain relatirely constant. Also, the drying shrinkage occurred greatly when the width and thickness of a member are small because it is easy to evaporate the inner part vapor in the small width and thickness of a member. there can be little different according to the location of a contact gauge, however it is similar to the change of specimen's length change. The concrete using crushed sands, of which grading, grain shape and fine particle is improved, are comparable to the quality of the concrete using washed sea sand.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.73-78
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• 2001

Portland cement concrete is made with coarse aggregate, fine aggregate, portland cement, water and, in some cases, selected chemical admixtures such as air-entraining agents, water reducer, superplasticizer, and so on, and mineral admixtures such as fly ash, silica fume, slags, etc. Typically, in the concrete, the coarse aggregate and fine aggregate will occupy approximately 80 percent of the total volume of the final mix. Therefore, the coarse and fine aggregates affect to the properties of the portland cement concrete. As the natural sands are drained, it is necessary and economical to utilize crushed sands(manufactured fine aggregate). It is reported that crushed sands differ from natural sands in gradation, particle shape and texture, and the micro fines in the crushed sands affect to the quality of the portland cement concrete. Therefore, the purpose of this paper is to investigate the characteristics of fresh and hardened concrete with high content of micro fines. This study provides firm data for the use of crushed sands with higher micro fines.

• 산업기술연구
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• 제21권A호
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• pp.285-292
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• 2001

The amount used of aggregates for concrete is increasing rapidly since the mid-1980s in Korea. The natural gravels from river are already displaced with crushed stone, and use of crushed sand as a substitute of natural river sands, also, is getting increased day by day. This paper is presented for mixture of high strength concrete using crushed sands. Mixing design of concretes are various water-cement ratios(w/c) such as 25%, 40%, 55% and different replacement ratio of crushed sands to natural sands such as 0%, 20%, 40%, 60%. As a results, it has been shown that compressive strength of concretes with w/c lower than 40% and 25% is higher than $400kgf/cm^2$ and $600kgf/cm^2$ respectively.

• 한국안전학회지
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• 제16권1호
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• pp.65-72
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• 2001

Portland cement concrete is made with coarse aggregate, fine aggregate, portland cement, water and, in some cases, selected chemical admixture such as air-entraining agents, water reducer, superplasticizer, and so on, and mineral admixture such as fly ash, silica fume, slags, etc. Typically, in the concrete, the coarse aggregate and fine aggregate will occupy approximately 80 percent of the total volume of the finished mixture. Therefore, the coarse and fine aggregates affect to the properties of the portland cement concrete. As the deposits of natural sands have slowly been depleted, it has become necessary and economical to produce crushed sand(manufactured fine aggregate). It is reported that crushed sand differs from natural sands in gradation, particle shape and texture, and that the content of micro fines in the crushed sand affect to the quality of the portland cement concrete. Therefore, the purpose of this paper is to investigate the characteristics of fresh and hardened concrete with higher micro fines. This study provides a firm data to apply crushed sand with higher micro fines.

• 한국농공학회지
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• 제44권2호
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• pp.107-116
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• 2002

The amount used of aggregates for concrete is increasing rapidly since the mid-1980s in Korea. The natural gravels from river are already displaced with crushed stone, and use of crushed sand as a substitute of natural river sands, also, is getting increased day by day. This paper is presented fur analysis on mechanical properties of high strength concrete using fly ash and crushed sand. The material functions in mixing design of concretes are various water-cement ratios(w/c) such as 0.25, 0.40, 0.55 and different replacement ratio of crushed sand to natural sands such as 0%, 20%, 40%, 60%. As a results, it has been shown that compressive strengths of concretes with W/C lower than 0.40 and 0.25 are higher than 400 kgf/$\textrm{cm}^2$ and 600 kgf/$\textrm{cm}^2$ respectively. It is also concluded that the results of rapid chloride permeability tests of concrete are evaluated to negligible. The conclusions of this study is that it is possible to use fly ash and crushed sand fur high strength concrete.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.656-661
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• 2009

In this study, theoretical analysis and evaluation tests were performed to assess the pipe stability against compaction equipments and vehicle loads when conventional construction criteria for pre-insulation heating pipes are applied and the alternative material, crushed sand, are used for backfills. The research outcomes shows that (1) the conventional code criteria for pre-insulated heating pipes is well established to support compaction equipments and vehicle loads, (2) the crushed sands as an alternative is usable as backfill materials for pre-insulated heating pipes based on the suitability evaluations of various types of pipes, and (3) the crushed sand agree well with the design consideration of pre-insulated heating pipes construction in the points of economical efficiency and construction criteria.

• International Journal of Concrete Structures and Materials
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• 제3권1호
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• pp.3-9
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• 2009

This paper examines the incorporation of the crushed sand (CS) and desert sand (DS) in the formation of self compacting concrete (SCC). These sands have been substituted for the rolled sand (RS), which is currently the only sand used in concretes and which is likely to run out in our country. DS, which comes from the Tunisian Sahara in the south, is characterized by a tight distribution of grains size. CS, a by-product of careers containing a significant amount of fines up to 15%, is characterized by a spread out granulometry having a maximum diameter of around 5mm. These two sands are considered as aggregates for the SCC. This first part of the study consists in analyzing the influence of the type of sand on the parameters of composition of the SCC. These sands consist of several combinations of 3 sands (DS, CS and RS). The method of formulation of the adopted SCC is based on the filling of the granular void by the paste. The CS substitution to the RS made it possible, for all the proportions, to decrease the granular voids, to increase the compactness of the mixture and to decrease the water and adding fillers proportioning. These results were also obtained for a moderate substitution of DS/CS (< 40%) and a weak ratio of DS/RS (20%). For higher proportions, the addition of DS to CS or RS did not improve the physical characteristics of the SCC granular mixture.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.205-210
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• 2002

As the deposits of natural sands have slowly been depleted, it has resulted in an increase in manufactured fine aggregate (MFA). Standard specifications for fine aggregate for concrete contained in KS F 2558 permit a maximum of 7 percent finer than the No. 200 sieve (75${\mu}{\textrm}{m}$). Since the production process for MFA normally generates 10 to 20 percent of micro fines-which is defined as aggregates passing the No. 200 sieve (75${\mu}{\textrm}{m}$)-more than permitted by specifications, Excess fines must be removed by screening and/or washing operations. The amount of by-products will continue to grow as production increases with environmental discharge restrictions. This fundamental study focuses on experimental research for the adequacy of use of micro fines included in crushed aggregate using methylene blue test. Total of 63 types of sands from seven different rocks were tested. Based on the test results, the methylene blue test was turned out to be a good indicator of the quality of micro fines for concrete and a supplementary article and an amendment of the KS standard were recommended.

• 한국광물학회지
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• 제19권4호
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• pp.355-361
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• 2006

국내에서 인공쇄석사의 점유율은 30% 이상이며 계속적인 증가추세에 있다. 국내 인공쇄석사는 주로 화강암류를 그 원암으로 이용하고 있다. 인공모래 제조공정 중에 생기는 스러지(63마이크론 이하입자)는 침전제를 이용하여 분리하며, 그 양은 중량비 15% 내외이다. X-선 회절분석에 의하면 스러지 구성광물은 석영, 장석류가 3/4 이상을 차지하며, 그밖에 방해석 등과 각종 점토광물류를 포함한다. 점토류 중에는 운모 및 고령토류가 우세하고, 녹니석, 질석과 함께 스멕타이트류도 포함된다. 쥬라기 화강암류에서 발생되는 스러지는 대체적으로 백악기의 것에 비해서 더 많은 고령토류, 녹니석 및 질석류를 포함한다. 화학조성에 있어서도 화강암류와 스러지의 사이에 명확한 차이를 보여준다. $SiO_2$ 및 $Na_2O$ 성분 외에는 스러지가 화강암 원석류보다 더 높은 함량을 나타내어, 그들이 풍화작용에 의한 증가임을 나타낸다. 스러지에 대한 입도분석에 의하면, 토양조직 분류에서의 Silt loam 정도에 해당하며, 변수두 투수실험에 의해 측정된 수리전도도에 의하여서도 silt 및 sand가 우세하게 포함된 특성을 나타낸다. 이와 같이, 현재 우리나라에서 버려지고 있는 스러지는 silt 및 점토입자함량에 의하여 불투수성을 야기하므로 산업폐기물로 간주되어 환경오염물로 분류되고 있다.