• Computers and Concrete
• /
• v.19 no.6
• /
• pp.617-623
• /
• 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.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.11 no.5
• /
• pp.88-92
• /
• 2002

This research is about slurry wear of SM45C and SUS304, which using standard sand and KUM river sand. The results are as follows ; 1. Mass loss rates of both standard sand and KUM river sand were linearly increased as increasement of time and velocity. 2. The average diameter of sand from relatively, less wear rate and portion of larger particles. 3. Wear resistance was linear with time and velocity of liquid jet regardless of type of sand. Also, it was able to evaluate with the formula, $HV^2$/E calibrated with n, the velocity index. 4. The wear surface in liquid jet experiment was smooth. The maximum wear depth was observed at the location 2~4mm apart from the center in the condition of $90^{\circ}$ of collision angle 6mm of nozzle diameter, and 20mm of collision distance. The sectional shape in radial appeared as 'W'shape.

• Journal of the Korea Concrete Institute
• /
• v.27 no.3
• /
• pp.273-281
• /
• 2015

In this paper, the performance of alkali-activated slag cement (AASC) is assessed in terms of compressive strength and drying shrinkage, using three different types of silica sand and river sand. The sand type has an important influence on the properties of AASC mortar. Three silica sands (SS1, SS2 and SS3) and river sand (RS) were considered. Three series of blended sands have been tested. A first series (S1) with RS and SS1, a second series (S2) with RS and SS2 and third series (S3) with RS and SS3 with a different blended ratios. The result shows a very significant influence of the blended sand on the AASC mortar properties. The compressive strength and drying shrinkage related with the particle sizes and blended ratios of sands are investigated considering blended sand properties like fineness modulus (FM) and relative specific surface. The type and blended ratio of sand seems to have very significant and important consequences for the mix design of the AASC mortar.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.27 no.4
• /
• pp.229-234
• /
• 2007

To select the most proper soil for root initiation from stem cuts of Birdsfoot trefoil (Lotus corniculatus L.), eight-week-old stem cuts were cultured on three types of soil [commercial bed soil, decomposed granite (DCG), and river sand] for one month. The results showed that the root initiation ratios on DCG (77.8%) and river sand (70.0%) were relatively high, but the ratio on commercial bed soil (41.1%) was very low. To examine the effect of rare earth (RE) and Indole-3-Butyric Acid (IBA) on root initiation from stem cuts of Birdsfoot Trefoil, stem cuts were cultured on two types of soil (DCG and river sand) with treatment of RE and IBA for one month. The root initiation ratios turned out to be 90.0% (DCG with 60 ppm of RE), 80.0% (river sand with 20 ppm of RE), 96.7% (DCG with 40 ppm of IBA), and 96.7% (river sand with 40 ppm of IBA). These results suggested that the most efficient way for root initiation of Birdsfoot trefoil was to culture the stem cuts on river sand or DCG over 30 days with IBA treatment (40 ppm).

• Journal of the Korean Society of Industry Convergence
• /
• v.2 no.1
• /
• pp.45-52
• /
• 1999

It is difficult to keep the balance of supply and demand for natural aggregates in recent years, because natural resources have become to be almost exhausted. Crushed stone is already used for coarse aggregate instead of river gravel at present. Now, crushed sand or sea sand should be used for fine aggregate, because natural sand also has been exhausted with a few exceptions around Nakdong River. The sea sand has a lot of problems which are the corrosion of reinforcement bars, the investment of facility for cleansing salt and the cost increase due to the insufficiency of industrial water. Therefore, it is necessary to produce and to utilize the crushed sand very actively, but some material properties which are related to water absorption, strength and chemical durability, prevent from determining the generalized criteria because its rocks make much differences in its physical and chemical characteristics. In this paper, fundamental physical properties of crushed sand, which comes from Daegu Subway construction fields, have been investigated for the usability on basic material of concrete. The optimum replacement ratio and the strength estimation method of crushed sand replacing natural sand also have been presented here through the compressive strength test of ready-mixed concrete cylinders.

• Korean Journal of Medicinal Crop Science
• /
• v.24 no.6
• /
• pp.479-485
• /
• 2016

Background: Planting vigorous cuttings that quickly develop shoots and roots is essential to the biological and economic success of producing medicinal flowers. The present study aimed to evaluate the effect of storage temperature and duration on seedling capacity in the propagation of Chrysanthemum indicum L. and to investigate the effect of rooting media on the growth of C. indicum L. after cutting. Methods and Results: Returning cuttings to supplemental cold storage ($2.0{\pm}1.0^{\circ}C$) may extend duration of cutting viability 6 weeks, returning cuttings to supplemental warm storage ($25.0{\pm}1.0^{\circ}C$) is not recommended. The treatment of the growing media experiments, which were conducted in the 2014 planting seasons, included sawdust, river sand, topsoil + sawdust, topsoil + poultry manure, sawdust + river sand, river sand + poultry manure, topsoil + river sand + poultry manure, topsoil + poultry manure + river sand + sawdust. Result indicated that the topsoil + poultry manure media performed best and supported the highest number of branches (3.47), branch length (26.39), and number of leaves (88.63). Conclusions: The results of the present study suggest that cold storage and the topsoil + poultry manure growth media was superior in supporting the early establishment of C. indicum cutting, this result will have a tremendous influence on propagation of this species.

• Korean Journal of Microbiology
• /
• v.24 no.3
• /
• pp.308-316
• /
• 1986

Vertical distribution of heterotrophic bacteria and physico-chemical characteristics were measuted in Kum River estuarine sediments. And interrelationship between heterotrophic bacterka and environmental factors was also studied. The type of sediment of Site 1 was silty clay, and sand at Site 2. Annual pH ranges were between 7.1 and 7.7 in the clay type sediment (Site 1) and 6.9-7.2 in the sand type sediment (Site 2). It was shown that organic matter contents were higher in the clay type sediment than those of sand type sediment. Redox potential values of sediments were decreased rapidly with depth at Site 1, but those of Sete 2 showed vertical fluctuation. Nitrogens(ammonia+amino acid-N, nitrate-N, nitrite-N) and phosphate in the clay type sediment showed higher values than those of sand type sediment. Annual distribution of heterotrophic bacteria were ranged $6.71{\times}10^4$ cells/g dry wt. $-2.50{\times}10^6$ cells/g dry wt. In the clay type sediment and $2.67{\times}10^3$ cells/g dry wt. $-1.94{\times}10^6$ cells/g dry wt. in the sand type sediment. Distribution of proteolytic, lipolytic, and amylolytic bacteria were decreased with the depth and the highest density was found in April and the lowest in January. Bacterial populations in sediments were closely correlated with such environmental factors as pH, redox potential, moisture content, organic matter contents, and inorganic nutrients such as nitrite-N and phosphate-P.

• Journal of the Korean Geotechnical Society
• /
• v.25 no.4
• /
• pp.105-112
• /
• 2009

In this study, a series of direct shear tests were performed to investigate the characteristics of friction angles for sands and interface friction angle between sands and construction materials with respect to different relative density of the Nak-dong River sands and shearing velocity. The result of the test shows that friction angles of sands are always higher than interface friction angle between sands and construction materials. As the shearing velocity get faster, the friction angles of sand became higher. With respect to the density of sand by reducing void ratio, friction angles increase linearly, and relevant equations were proposed to calculate the friction angle by changing void ratio and relative density of sand. The interface roughness of construction materials was also an important factor in interface friction angle.

• Journal of the Korean Geotechnical Society
• /
• v.23 no.2
• /
• pp.35-45
• /
• 2007

In this research, artificially cemented sand which is made of a few portland cement and Nak-Dong river sand was researched closely. For providing the fundamental data which is needed in design and analysis of levee material, the shear behavior of cemented sands was investigated by drained triaxial test, and analyzed in accordance with the increase of cement content. The peak strength and elasitc modulus increased and dilation of cemented sand was restricted by the cementation, but after breakage of the cementation, dilation increased, cohesion intercetpt and friction angle increased with the increase of cement content and strain softening behavior appeared in stress-strain curve.

• Journal of the Korean GEO-environmental Society
• /
• v.7 no.4
• /
• pp.43-52
• /
• 2006

There were huge damages of human beings and their properties in many areas of the basin of the Nak-Dong river by the unusual weather and the localized downpour recently. In this research against disasters, we want to know strength of the cemented sand that is mixed with cement and poor-graded sand, to estimate CSG(Cemented Sand and Gravel) method used coffer dam in Japan, which is the materials of riverbed in the basin of the Nak-Dong river for levee's construction. For that, we want to provide the fundamental data which need in the examination of adaptation of levee's material, design and analysis by investigating compressive strength by curing period and cement content, elastic modulus and stress by transformation from compaction test, CBR test, unconfined compression test and triaxial compression test as changing cement content from 2% to 8% at two sites in the basin of the Nak-Dong river.