• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.213-216
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• 2004

Aggregate occupies about 70 to 80 percent by volume in concrete as skeleton of concrete, but recently, it has been insufficient in quantity to collect good natural aggregate because of exhaustion of aggregate resources. In case of Korea, in 2002, the using ratio of crushed stone occupies about $97\%$ of whole coarse aggregate, and ratio of crushed sand occupies about $18.3\%$ of whole fine aggregate. This is an experimental study to compare and analyze the properties of concrete according to the grading of crushed stone to improve quality and mix design of concrete using crushed stone. According to results, it was found that grading level of crushed stone in the range of G42 to G60 was better than any other grading level in terms of fluidity and compressive strength. And it is considered to be in the range of 6.52 to 6.85 in terms of FM.

• Journal of the Korean Geosynthetics Society
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• v.5 no.1
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• pp.33-38
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• 2006

Large-scale direct shear tests were conducted in order to evaluate both the shear strength of crushed stone itself and the interface shear strength between crushed stone and geotextile. Total three types of geotextile (i.e. one woven geotextile and two nonwoven geotextiles) were used in the experimental program, considering two different values for the unit weight of crushed stone. Total fifteen tests were conducted in this study. It has been found from the experimental results that the friction angles of crushed stone itself were $47^{\circ}$ and $57^{\circ}$ under the unit weights of crushed stone being $1.4t/m^3$ and $1.5t/m^3$, respectively. Interface friction angle between nonwoven geotextile and crushed stone showed $39^{\circ}$ for type A indicating an efficiency of 83% and $42^{\circ}$ for type B indicating an efficiency of 89%. Similarly, interface friction angle between woven geotextile and crushed stone showed $39^{\circ}$ indicating an efficiency of 83%.

• Journal of the Korean GEO-environmental Society
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• v.7 no.6
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• pp.67-73
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• 2006

In this study, basic physical tests and mechanical tests of crushed rock were performed in order to investigate the field application of crushed rock as substitute materials of sand that is commonly being used as foundation and backfill materials of sewer conduit. Particle-size distribution curve of crushed rock is similar to sand and also it is well-graded soil than common sand. Maximum dry unit weight in proctor compaction test for crushed rock is higher than the values of common sand. So we can estimate that the crushed rock has advantages in workability than sand for the backfill compaction after construction of sewer conduit. When we investigate the results of direct shear test and triaxial compression test on the crushed rock, it has a similar value of shear strength parameters to sand at the same stress state and as time goes by, it tends to increase the unconfined compression strength. But, because the strength reaches at the constant value after 6~7 days, we expect that it can absorb the lateral strain of flexible conduit well. All the above experimental results just proves that crushed rock can substitute for sand as backfill materials and foundation of sewer conduit.

• Journal of Korean Medicine Rehabilitation
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• v.21 no.2
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• pp.143-158
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• 2011

Objectives : Peripheral nerve injuries are commonly encountered clinical problem and often result in severe functional deficits. The aim of this study is to evaluate the effects of aqueous extract of Achyranthes japonica(AJ) on functional recovery in sciatic nerve after crushed sciatic nerve injury. Methods : In the present study, the animals in the AJ-treated groups received the aqueous extract of AJ at the respective doses orally for 13 consecutive days. In order to assess the effects of the aqueous extract of AJ on function recovery in crushed sciatic nerve injury, sciatic functional index(SFI) was performed. c-Fos expression in the paraventricular nucleus(PVN) and ventrolateral periaqueductal gray(vIPAG), and neurofilament, and the expressions of brain-derived neurotrophic factor(BDNF), nerve growth factor(NGF) following crushed sciatic nerve injury in rats were investigated. For this, immunohistochemistry and western blot were performed. Results : In the present study, crushed sciatic nerve injury showed characteristic gait changes showing decrease of SFI value and treatment with the aqueous extract of AJ significantly enhanced the SFI value. Neurofilament expression in the sciatic nerve was decreased by crushed sciatic nerve injury and treatment with the AJ increased neurofilament expression. The expressions of BDNF and NGF in the sciatic nerve were increased following crushed sciatic nerve injury and treatment with the AJ significantly controlled the sciatic nerve injury-induced increment of BDNF and NGF expressions. c-Fos expressions in the PVN and vIPAG were increased following crushed sciatic nerve injury and treatment with the AJ significantly suppressed the sciatic nerve injury-induced increment of c-Fos expressions. Conclusions : These results suggest that AJ treatment after crushed sciatic nerve injury is effective in the functional recovery by enhancing axonal regeneration and suppressing of pain.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.3
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• pp.244-251
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• 2015

The paper evaluates the effect of the physical property, fineness modulus (FM) and replacement ratio of crushed sand on the characteristics of concrete. This is intended to use crushed sand from Daegu-Kyungbuk region as the fine aggregate of concrete. The experimental result indicates that the replacement ratio of crushed sand needs to be less than 50% to satisfy the mixed gradation of both natural and crushed sand when their FMs are 2.0 and 3.2, respectively. The slump of concrete with crushed sand increased as the replacement ratio of crushed sand increased, while the workability of concrete with the replacement ratio of more than 75% was significantly reduced. The air content and bleeding rate of concrete was reduced as the replacement ratio increased. Furthermore, due to the enhancement of the concrete adhesive regardless of the FM of crushed sand, compressive strength of concrete tended to improve as the replacement ratio increased.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.229-236
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• 2006

Recently, the use of crushed sand produced by the crushing of stone is continuously increasing to reach an utilization rate of about 20% of the whole fine aggregates that is foreseen to grow larger in the future. However, the lack of recognition concerning quality during the production of crushed sand results in the use of crushed sand that do not satisfy the KS F 2527 standard during the manufacture of concrete. And, studies investigating the effects of such crushed sand on concrete are still neglected. Therefore, this study intends to provide data that can be exploited for concrete using crushed sand through the analysis of the effects of the grain shape of crushed sand on the quality of concrete. Results revealed problems in the workability, air entraining and durability for a value of 53% for the solid volume percentage for shape determination specified by the current KS F 2527. Analysis showed that the adjustment of the solid volume percentage for shape determination from the currently specified 53% to 55% will improve the quality of concrete using crushed sand in high strength concrete particularly.

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

• Food Science and Preservation
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• v.7 no.2
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• pp.222-227
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• 2000

Antimutagenic activity of crushed kimchi fermented with starter under various conditions such as temperature(5-20$^{\circ}C$), salt concentration(2-10%), addition rate of starter (0-20%) was investigated. The kimchi was fermented with crushed Chinese cabbage without salting, red pepper powder, crushed garlic, crushed ginger, anchovy juice and starter. Well fermented kimchi juice(fermented at 10$^{\circ}C$ for 15 days) and sterilized radish juice was used as a source of lactic acid bacteria and starter medium, respectively. Antimutagenic activity showed the highest in the crushed kimchi fermented at 15$^{\circ}C$ for 15 days, 4% salt concentration, 5% starter added, respectively. The inhibition rate of mutagenic activity of the kimchi against S. typhimurium TA98 induced by NQO and S. typhimurium TA100 induced by MNNG was 56.41% and 60.11%, respectively. And the inhibition rate of the kimchi juice showed 56-60% per 100ul.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.339-342
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• 2000

Recently, the importance of the conutermeasures for waste materials has pointed out. Waste glass is also one to waste materials used for the recycling in construction sites. The crushed waste glass has been used to make a glass polymer composite that can be applied for sewer, storm drain pipe and interlocking block, etc. In this study, the crushed waste glass is explored with the possibility of recycling it, as a substitute for fine aggregates. The prepose of this investigation is to improve the strengths and acid resistance of the UP mortars using crushed waste glass. The UP mortars are prepare with blast furnace slag fly ash filler. the UP-fine aggregate ratios the crushed waste glass replacements for fine aggregate are tested strengths before and after immersion(H (아래첨자2)SO(아래첨자4) 10%), weight change and acid resistance are also tested. From the test results, the relative strength or UP mortars using fly ash as filler are found to be somewhat superior to that of the UP mortars using blast furnace as filler, And a UP mortar with fly ash as a filler, a UP-fine aggregate ratio of 15% and a waste glass replacement if 50% for fine aggregate is recommended as optimal mix proportion of UP mortar using crushed waste glass. Accordingly, it is enough to assure the use of the crushed waare glass as an aggregate for the production of UP mortar.

• Journal of the Korea Institute of Building Construction
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• v.3 no.3
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• pp.107-112
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• 2003

This study is to investigate the properties of concrete with crushed sand on site and to propose a quality guideline for its use as artificial sand and concrete. From our experimental result in laboratory and site, we found that demand water of concrete with crushed sand for target slump increased by 18kg/m3 compared to mixed sand and l8kg/m3 compared to sea sand respectively. The compressive strength increased by around 3∼6% when compared to concrete with sea sand. Accordingly, our study showed that the combined sand mixed with sea sand would be desirable to obtain workability and strength of concrete including dry shrinkage and bleeding test. Furthermore, the optimal replacement percentage of crushed sand was 50% with sea sand. As such, crushed sand would be sufficient as fine aggregate for concrete in terms of economic efficiency and quality. Crushed sand, on the other hand can only be used as fine aggregate when VFS(Very Fine Sand) is below 3.5 percentage of weight of sand and particle shape is above 55 percentage. Also, the particle shape and microsand passing NO.200 sieve should continually be improved to increase workability of concrete on site.