• Journal of the Korea Concrete Institute
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• v.28 no.2
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• pp.205-212
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• 2016

This research investigates the influence of ground granulated blast furnace slag (GGBFS) composition on the alkali-activated slag cement (AASC). Aluminum oxide ($Al_2O_3$) was added to GGBFS binder between 2% and 16% by weight. The alkaline activators KOH (potassium hydroxide) was used and the water to binder ratio of 0.50. The strength development results indicate that increasing the amount of $Al_2O_3$ enhanced hydration. The 2M KOH + 16% $Al_2O_3$ and 4M KOH + 16% $Al_2O_3$ specimens had the highest strength, with an average of 30.8 MPa and 45.2 MPa, after curing for 28days. The strength at 28days of 2M KOH + 16% $Al_2O_3$ was 46% higher than that of 2M KOH (without $Al_2O_3$). Also, the strength at 28days of 4M KOH + 16% $Al_2O_3$ was 44% higher than that of 4M KOH (without $Al_2O_3$). Increase the $Al_2O_3$ contents of the binder results in the strength development at all curing ages. The incorporation of AASC tended to increases the ultrasonic pulse velocity (UPV) due to the similar effects of strength, but increasing the amount of $Al_2O_3$ adversely decreases the water absorption and porosity. Higher addition of $Al_2O_3$ in the specimens increases the Al/Ca and Al/Si in the hydrated products. SEM and EDX analyses show that the formation of much denser microstructures with $Al_2O_3$ addition.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.473-476
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• 2008

Due to the pursuit of high function and international price increase in the field of construction, the application of the secondary product using cement is on the increase gradually in the construction industry in the pursuit of economic cost reduction by the shortening of the construction time like Expediting and the dry construction method at the same time. However, it is in very urgent situation of measures to improve the structural performance or durable performance because it is limited for use in terms of panel in interior exterior building or functional repair reinforce as yet. Accordingly, this study is to investigate applicability of permanent Formwork like mould with the structural performance or excellent durable performance in the field of construction, and to derive optimum mixture in the performance and quality of manufacture. As a result of analysis comparison with the dynamic and durable properties of vacuum extrusion molding high toughness cement panel according to the mixture of four conditions, this study has found that the test body of mixing ECC-DP3 using small filler and large granulated blast furnace slag and powder flame retardant had excellent relative hardness and bending stress strain. The durable performance has shown excellent tendency by the decrease of porosity and enhancement of water-tightness.

• Journal of the Korea Concrete Institute
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• v.29 no.3
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• pp.307-314
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• 2017

Concrete is a durable and cost-benefit construction material, however performance degradation occurs due to steel corrosion exposed to chloride attack. Penetration of chloride ion usually decreases due to hydrates formation and reduction of pores, and the reduced chloride behavior is considered through decreasing diffusion coefficient with time. In the work, HPC (High Performance Concrete) samples are prepared with 3 levels of W/B (water to binder) ratios of 0.37, 0.42, and 0.27 and 3 levels of replacement ratios of 0%, 30% and 50%. Several tests containing chloride diffusion coefficient, passed charge, and compressive strength are performed considering age effect of 28 days and 180 days. Chloride diffusion is more reduced in OPC concrete with lower W/B ratio and GGBFS concrete with 50% replacement ratio shows significant reduction of chloride diffusion in higher W/B ratio. At the age of 28 days, GGBFS concrete with 50% replacement ratio shows more rapid reduction of chloride diffusion than strength development, which reveals that abundant GGBFS replacement has effective resistance to chloride penetration even in the early-aged condition.

• Korean Journal of Organic Agriculture
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• v.14 no.2
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• pp.205-217
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• 2006

This research was carried out to investigate the effects of some organic materials such as rice straw, compost, hairy vetch, phosphate rock, magnesium lime powder and ash in the organic paddy fields, and also to develope the new technique for better soil management using described materials. The results are as follows; Height and tiller of rice plants were higher in chemical fertilizer than rice straw or compost, however, those of rice plants in hairy vetch-rice cropping system reached to chemical fertilizer. The Eh value of soil has decreased consecutively since on 30th, May because of the rising of soil temperature by an increase in the activity of microbes. As a result of measuring yield and yield components, there is not significant difference between treatment. The application of organic materials enriched the contents of available phosphorus, exchangible potassium and calcium in soil, and, also improved the physical properties such as pore space rates and bulk density. From the viewpoint of soil management technology in organic paddy fields, the application of rice straw or organic compost might cause the decrease of yield compared with conventional cultivation system, chemical fertilizer, however, the application of hairy vetch residues of soil compensated for growth and yield as well as improved the physicochemical property. Therefore, it is assumed that the cultivation of hairy vetch for winter season can be one of the useful methods for organic farming system.

• Korean Journal of Agricultural Science
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• v.14 no.2
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• pp.329-344
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• 1987

This paper described the behavior under repeated loading in triaxial compression test on clay. The experiment was conducted to investigate the influence of controlled various over-consolidation ratio and compaction energy, on the stress-strain behavior of clays. 1. The difference of deviator stress during repeated loading was greatly appeared at large strain. And pore water pressure was decreased at initial of unloading, but it was increased again before long. 2. The recoverable elastic strain (${{\Delta}{\varepsilon}e}$) and the slope of un-reloading were decreased with the increment of over-consolidation ratio (OCR). 3. The recoverable elastic strain (${{\Delta}{\varepsilon}e}$) was increased with the increment of strain rate but it was decreased with the increment of strain in strain rate tests. The slope of un-reloading (Eur) tends to increase with the increment of strain rate and it was decreased with the increment of strain. 4. The recoverable elastic strain was greatly increased with the increment of compaction energy and it slightly tends to decrease with the increment of strain on various compaction energy. The slope of un-reloading was not appeared markedly with increment of compaction energy but it tends to decrease with the increment of strain generally.

• Korean Journal of Organic Agriculture
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• v.23 no.4
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• pp.813-827
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• 2015

This study was conducted to evaluate the effect of organic inputs on soil properties in a newly reclaimed organic soils. The soil of the experiment site was very low in soil fertility and the physico-chemical properties were poor. Several organic input treatments with different source of nutrient were placed, including compost in combination with green manures for organic agricultural practices, chemical fertilizers for conventional agricultural practices, and control without fertilizer. The experiment was conducted with continuous cropping system during 3 years. The chemical properties concentration in compost+green manure treatment was increased continually compare to control and chemical fertilizer treatment, and closed to the recommended rate of fertilizer. The organic matter value for compost+green manure treatment was increased from 0.86~0.96% to 2.00~2.29% by continuous nutrient supply of compost and green manure. However, further investigation on increasing of organic matter value for 3 years is necessary to monitor carefully during the long-term because it will help to clarify the all mechanisms of organic matter on organic input application way. The available phosphate value for compost+green manure treatment was generally increased from 21.9~27.1 mg/kg to 182.0~394.1 mg/kg. In case of exchange cation, the concentration for compost+green manure treatment was increased during 2 years within the range to the recommended rate of fertilizer, however, it is expected to cause a rather over supply for 3 years.

• Korean Journal of Soil Science and Fertilizer
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• v.25 no.2
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• pp.175-180
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• 1992

The occurrence of internal cavity of in red ginseng is one of critical quality criteria. The occurrence of internal cavity mainly due to fresh ginseng character that is determined by growth conditions. Growth conditions and percent occurrence of internal cavity were investigated on various ginseng plantations for 6 years and the relation. ships among them were statistically analysed. In addition, field experiments were carried out seperately for the effect of special factors. 1. Internal cavity in red ginseng mainly occurred on area between central part and cortex part of tap root in red ginseng. It was suppose to be caused by characteristics of fresh ginseng. 2. Soil moisture decreased percent occurrence of internal cavity(PIC) above 27.5 % of PIC and increased below it. 3. The factors of shade structure with high intensity of light condition tend to increase PIC. PIC was decreased below 15.9 % of light transmittance rate and increased above it.

• The Journal of Engineering Geology
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• v.3 no.1
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• pp.21-37
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• 1993

In order to investigate the correlation of sedimentary rock properties. specific gravity, porosity, water content, sonic wave velodty, and point4oad strength index of core samples of limestones, sandstones and shales were measured. The relationships between density and velocity show $V_p=16300d-38719.3,{\;}V_s1896.4d-29225.1$ of regression equation for sandstones and $Vp=4085d-10264.8,{\;}V_s=3519d-7841.3$ for shales and <$Vp=4085d^2-20747d+303,{\;}V_s=3899d^2-21442d+318$ for limestones. Seismic wave velocity of shales which have high density is lower than that of sandstones, and this seems to be an effect of bedding in shale. P-wave velocity and S-wave velocity of limestones, sandstones and shales show the linear relationships as a whole. The regression equations are respectively calculated V_s=0.26V_p+1041.6m/sec,{\;}V_s=0.43V_p+424.2m/sec,{\;}and{\;}Vs=0.51V_p+261.9m/sec$ and the correlation coefficients of the velocity show r= 0.86 in sandstones, r= 0.75 in limestones and r=0.86 in shales. According to the point4oad strength test for limestones, point4ord strength anisotropy was not so dear even though the specimens show generally the banded structure. Variations of dip angle of bedding whihin the range $30^{\circ}-60^{\circ}$ does not have much influence upon the diametral strength index and axial strength index. From the result of point load test, P-wave velocity increases with point4ord strength index but the regression equations are $V_p=98.5lI{s_d}+4082.1m/sec,{\;}V_p=106.41{s_a}+3954m/sec$ and their correlation coefficient is low.

• The Journal of Engineering Geology
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• v.21 no.2
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• pp.147-156
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• 2011

We conducted laboratory experiments to determine the physical and mechanical properties, and the failure behaviors, of cements for use as grouting material in a $CO_2$-injection borehole. Samples with lour different ratios of water to cement mass (0.4, 1, 2, and 3) were tested. The analyzed properties (porosity, sonic velocity, modulus, and compressive and tensile strengths) varied systematically as a function of the ratio of water to cement (w/c), showing a sharp change between w/c ratios of 0.4 and 1. Triaxial compression tests revealed a clear boundary between brittle and ductile failure depending on the w/c ratio and confining pressure. The present results can be utilized as input parameters for numerical models to understand the initial deformation and failure behavior of grouting cements in a $CO_2$-injection borehole.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.51 no.7
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• pp.593-598
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• 2006

This study was conducted to investigate the effect of tillage methods such as plowing and rotary tillage (PRT), rotary tillage (RTG), no-tillage after barley straw application (NTB), and barley straw mulching after plowing and rotary tillage (BPR) on the growth and the yield of soybean when cultivated after the cultivation of barley. The methods were compared with the control method in which plowing and rotary tillage after barley straw incineration was applied. Barley straw application resulted in increase in organic matter, total nitrogen, phosphate, and exchangeable cation regardless of tillage methods. Porosity and moisture level in paddy soil was ranked as follows : PRT > RTG > BPR > control > NTB. Decomposition rate of barley straw dramatically increased to 41.7% toward 30 days after soybean sowing, higher in NTB, DRB, and RTG than in BPR. Weed occurrence was decreased 36% in NTB and 40% in BPR. Root activity, nodulation and the dry weight per plant of soybean at flowering stage were highest in NTB and lowest in PRT. Soybean yield in NTB was 3,070 kg/ha increasing 19%, whereas that in PRT was not increased. Therefore in case of a frequent rain during the cultivation of soybean in paddy field PRT could result in excess moisture level in soil, the cultivation without tillage is desirable.