• 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.

• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.415-423
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• 2006

As the shortage of natural & good quality aggregate for concrete, it is needed development of alternative aggregate. At the present time, the crushed sand is widely used among the alternation aggregate, and the usage of crushed sand will be increased more and more. Generally, crushed sud is produced with wet process in domestic, but some manufacturing companies which are handicapped with local restrict are produced by dry process. In this study, analyzing the facilities of dry crushed sand, the quality properties of dry crushed sand was done by Korean Industrial Standards. Based on the quality results of dry crushed sand, the experiment of concrete with the dry crushed sand which is substitute for sea sand was done. As the results of basic qualities, the amount of 0.08 mm sieve passing ratio was over KS criteria, and the fineness modulus was higher than sea sand, and the other physical properties of dry crushed sand was similar to sea sand. The results of concrete experiment, according to the substitutive ratio of dry crushed sand is increased, the slump and air content of concrete was decreased by increase of fine particles of dry crushed sand, and the unit weight content, compressive & tensile strength of concrete were increased on the contrary. The physical properties of concrete used dry crushed sand were showed same tendency without relation to W/B. Consequently, if the fine particle contents of dry crushed sand was lower, it is judged that dry crushed sand is no problem to use for concrete aggregate and the amount of usage will be increased.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2009.05b
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• pp.81-85
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• 2009

This study was to execute the basic property evaluation of recycled sand which produced by the sand flux device in order to evaluate the performance of differences between small large sand flux device. As a result, this study has found out that the recycled sand after passing the sand flux device had excellent quality characteristics compared with the One before passing the device. In additional experiment On the basic material properties, this study showed a tendency to improve the quality and performance significantly in case of fineness modulus, absolute surface dried density, 0.08mm sieve throughput, volume of clay lumps, and content of organic foreign matter. In conclusion, it was considered as various quality performances of recycled sand were improved through the production stage of prototype.

• Journal of The Korean Society of Grassland and Forage Science
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• v.8 no.1
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• pp.55-60
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• 1988

A two year's field experiment was conducted on newly reclaimed saline tidal lands to measure the effects of sand mulching on salinity of the soils and their relationship to crop performance. Hybrid sorghum cv. Pioneer 931 was grown under different mulching treatments using of medium sand and red earth (Fine loamy, Typic Hapludults). Salinity in the root zone was decreased markedly under soil mulching using of medium sand, especially during the dry season, and it caused a great increase in the root growth and R/T ratio. Seasonal values of electrical conductivity at sand mulching were 6.6 in April and 1.6 mmhos in August, but it was still high with a concentration of 12.7 (April) and 3.8 mmhos (August) in untreated check plot. Sand mulching increased plant growth and the rate of dry matter accumulation. However, treatment of red earth additionally over sand mulching produced lower dry matter yield than those of soil mulching using of medium sand only. Under salt stress sorghum plant showed a decrease in the leaf weight ratio (LWR) and it resulted in a low concentration of crude protein of the plant. Sand mulching enhanced leaf weight ratio and rate of protein synthesis.

• Advances in concrete construction
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• v.9 no.6
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• pp.589-596
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• 2020

In an effort to find alternate, environment friendly and sustainable building materials, the scope of possible utilization of iron slag (I-sand), generated as a by-product in iron and steel industries, as fine aggregates in reinforced cement concrete (RCC) made with manufactured sand (M-sand) is examined in this manuscript. Systematic investigations of the physical, mechanical, microstructural and durability properties of I-sand in comparison with RCC made with M-sand have been carried out on various mix designs prepared by the partial/full replacement of I-sand in M-sand. The experimental results clearly indicate the possibility of utilizing iron slag for preparing RCC in constructions without compromising on the property of concrete, durability and performance. This provides an alternate possibility for the effective utilization of industrial waste, which is normally disposed by delivering to landfills, in building materials which can reduce the adverse environmental effects caused by indiscriminate sand mining being carried out to meet the growing demands from construction industry and also provide an economically viable alternative by reducing the cost of concrete production.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.2
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• pp.83-92
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• 2006

Recently, interest grew recently on the quality of aggregates following the diminution of primary resources from river and the growing construction demand which exhausted high-quality sand sources around large cities and incited the use of low grade aggregates like shore sand and sea sand that can be supplied in natural state. Especially, the environmental preservation concern and the augmentation of public grievance about the exploitation of sea sand as substitute to river sand are gradually impeding the supply. This situation aggravated by the recent interdiction to extract sea sand which resulted in sand crisis that even led once to the suspension of construction works. The lack of sea sand and river sand increased the exploitation of crushed sand which occupies now nearly 20% of the whole quantity of fine aggregates. And, the use of crushed sand may be expected to grow continuously in the future. This paper described that the properties of crushed sand and the concrete using the crushed sand, the technologies to improve quality of crushed sand and the concrete in order to provide information for the production of high-quality concrete using crushed sand.

• Korean Journal of Organic Agriculture
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• v.8 no.1
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• pp.79-88
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• 1999

In order top investigate the growth of water dropwort grown by sandculture irrigated with recirculated tilapia aquaculture water, these experiments were carried out. Fish(tilapia) production and biofiltration provided by sand cultured water dropwort(Oenanthe stolonifera DC.) were linked in a closed system of recirculation water. Water dropwort was irrigated with water drawn from the tilapia tank and drainage from sand beds was returned to the fish tank. The temperature, pH and EC of tilapia culture water were stable. The growth of water dropwort grown by sandculture with aquaculture water was normal. Microbial activity of the biofilterbed irrigated by tilapia rearing water was higher than that of biofilterbed irrigated by tapwater. The feasibility of an integrated, recirculatory system for concurrent production of water dropwort and fish with no additional fertilization application was demonstrated.

• Journal of Sericultural and Entomological Science
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• v.39 no.2
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• pp.101-105
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• 1997

Most of the mulberry saplings in Korea have been produced by grafting. But the production of mulberry sapling by this method is very complex process and requires high level of technique and two years to produce saplings. Therefore, to develop the mulberry sapling production system by softwood cutting method which is suitable for mass production, several conditions on rooting and growth of cuttings were investigated. The rooting ability of cuttings varied according to mulberry varieties, showing the highest rooting ratio of 93.3% in cultivar of Shingwangppong. Of different soil texture as for rooting media, the clay was found to be the best; other media decreased in order as follows; sand, sand loam and vermiculite. The shading ratio by 70% with polyethylene film showed the highest rooting ratio of the cuttings. Optimum day of cutting was around 50th day after sprouting, whereas the ratio of stem thicker than 7mm at the base of saplings in diameter was highest at 44th day.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.4 no.5
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• pp.1-10
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• 1981

The purpose of this study is to cut down cost of production and improve the productivity of industry through quality improvement of castings and reduction of defectives by applying the experimental design to the foundry sand mixing operation done at molding department in the foundry. Among the related foundry sand mixing factors which have an effect on casting the experiment of which factors have a dominant effect on quality improvement was performed between two different levels by means of "$2^n$ type orthogonal array." The results cail be summarized as follows ; (1) The optimum conditions per each foundry sand mixing between two different levels proved to be such as $A_2$(used sand) : 24 unit (172.8kg), $B_2$(unused sand ) : 2 unit (15.0kg), $C_2$(binder) : 2.5 unit (4.4kg). $D_2$(addition agent) : 1 unit(1.4kg) and $F_1$(moisture) : 7.4%(14.6kg). (2) As a result of the application of experimental design, the fraction defective during the foundry sand mixing operation turned out to be reduced front 6.6% to 2.04%. (3) For the purpose of cost-down, It was found that the optimum level decision of foundry sand mixing for various castings is required to be made by means of experimental design.al design.

• Advances in concrete construction
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• v.13 no.6
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• pp.461-470
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• 2022

Solid waste management is of great concern in today's world. An enormous amount of waste is generated from various industrial activities. Concrete production utilizing some of the potential waste materials will add to the benefit of society. These benefits will include reduction of landfill burden, improved air quality, riverbed protection due to excessive sand excavation, economical concrete production and much more. This study aims to utilize waste granite powder (GP) originating from granite industries as a sand replacement in concrete. Fine GP was collected in the form of slurry from different granite cutting industries. In this study, GP was added in an interval of ten percent as 10%, 20%, 30%, 40% and 50% by weight of sand in concrete. Mechanical assets; compressive strength, flexural strength and splitting tensile strength were prominent for control and blended mixes. Modulus of elasticity (MoE) and abrasion tests were also performed on control and blended specimens of concrete. To provide a comprehensive clarification for enhanced performance of GP prepared concrete samples, scanning electron microscopy (SEM) and X-ray diffraction (XRD) were performed. Results indicate that 30% replacement of sand by weight with GP enhances the mechanical assets of concrete and even the results obtained for 50% replacement are also acceptable. Comprehensive analysis through SEM and XRD for 30% replacement was better than control one. The performance of GP added to concrete in terms of abrasion and modulus of elasticity was far better than the control mix. A significant outcome shows the appropriateness of granite fines to produce sustainable and environmentally friendly concrete.