• Journal of the Korea Institute of Building Construction
• /
• v.13 no.3
• /
• pp.282-290
• /
• 2013

In this study, the adjustment range of mixture factor with replacement mineral admixture was reviewed to secure the mixture change data of high volume concrete compared to general concrete. When changing the concrete mix to high volume concrete within the universal concrete mixing, the adjustment range of mixture to ensure optimum quality is as follows. Unit-water content is $20{\sim}30kg/m^3$ downward. Fine aggregate ratio dropped by approximately 1% when W/B was reduced by 5%, and it is reduced by approximately 0.12% when there is a 5% increase in the total replacement rate. When the FA replacement rate was increased by 5%, the AE agent was approximately 20% to 30% higher compared with the conventional one. When the FA and BS replacement rate rose by 5%, W/B was reduced by about 1 to 4%.

• Magazine of the Korea Concrete Institute
• /
• v.7 no.2
• /
• pp.155-164
• /
• 1995

This study was performed to get high strength of the precase concrete adopting a steam curing by using a gypsum-admixture for the high strength concrete. The superplasticizer was used to compensate low slump of base concrete keeping its slump up about $6{\pm}1cm$. To examine the property for strength revelation of concrete using admixtures for a high strength concrete, steam and standard curing were compared each other. Test results were shown that admixtures for high strength concrete were more effective in steam curing than standard curing. On the condition that the unit cement content is about $530{\sim}600kg/m^3$, the compressive strength of concrete replacing by 10% of the admixture was obtained over $65Okgf/cm^2$, which was increased as 1.3 times as that for the nonreplacement. When the admixture was replaced to 15-30%, the compressive strengh was obtained over $700kgf/cm^2$ which was increased as 1.4 - 1.5 times. Therefore, the admixture for high strength concrete, being effective in steam curing, was more efficient to get a high strength concrete using only steam curing instead of an autoclave curing for the secondary products of cement.

• Journal of the Korea Concrete Institute
• /
• v.16 no.3 s.81
• /
• pp.303-310
• /
• 2004

The purpose of this study was to investigate the effect of using method and replacement ratio of limestone powder and water-cement ratio on the compressive strength and the resistance to sulfate attack of mortar incorporating limestone powder as fundamental study to use limestone powder as an addition for concrete. As a results, The method using limestone powder as a part of cement showed decrease of the compressive strength of mortar. The strength of mortar incorporating limestone powder almost decided upon unit cement content. It was recognized that the method replacing limestone powder as a part of cement was effective to decrease the heat of hydration in concrete. The method using limestone powder as a part of fine aggregate showed the considerable increase of the strength and resistance to sulfate attack of concrete. Furthermore, it was recognized that the method using limestone powder as a part of fine aggregate were effective materials as an addition for concrete in view of the improvement of strength and resistance to sulfate attack.

• Journal of the Korean Home Economics Association
• /
• v.27 no.1
• /
• pp.39-46
• /
• 1989

Mung bean starch gel (Mook) and gel made from starch of cowpea are similar properties in texture. In order to elucidate the similarity between these two starch gels, some physicochemical properties of cowpea starch were compared with those of mung bean starch. Water bildings capacity of cowpea starch (183.6%) was a little low than that of mung bean starch (184.2%). The solobility, swelling power and optical transmitance of the cowpea starch showed a smiliar pattern to mung bean starch, but cowpea starch had a little lower solubility than mung bean starch. Amylogram of mung bean strach (4, 5, 6, 7%) shoved no peak viscosity but cowpea starch (4, 5, 6%) showed peak viscosity and both starches showed high viscosities when cooling. Cowpea and mung bean starches had the blue value of 0.41 and 0.47, the alkali number of 8.4 and 8.0, the amylose content of 30.5 and 32.1%, the molecular weight of amylose of 30,000 adn 29,258 and glucose unit per segment of amylopectin of 27.6 and 26.8 respectively. The shape of cowpea and mung bean strach granules were round and elliptical, and the mean vlalue of major axis, minor axis and the ratio of these were 20.7 and 21.8 ${\mu}{\textrm}{m}$, 14.6 and 14.4 ${\mu}{\textrm}{m}$ and 1.42 and 1.51, respectively. The extent of retrogradation determined by the glucoamylase digestion method and syneresis showed that cowpea starch gel was larger than that syneresis showed than cowpea starch gel was larger than that of mung bean starch gel. The redults of X-ray diffraction studies showed A pattern for two starches, Diffraction peak of gels disappeared with gelatinization of starches but that of two starch gels storaged for 2 days at 5$^{\circ}C$ showed a similar patterm.

• Journal of the Korean GEO-environmental Society
• /
• v.11 no.10
• /
• pp.15-24
• /
• 2010

In the case of underground power utilities pipe such as circular pipe, the most difficult problem is low compaction efficiency of the bottom of pipe inducing the failure of utilities. To overcome this problem, various studies have been performed and one of these is CLSM(Controlled Low Strength Materials) accelerated flow ability. But underground power utilities pipe backfill materials is also needed to have good thermal property that can dissipate the heat as rapidly as it is generated. So, in this study, we performed thermal resistancy test for various materials such as sand, weathered soil, clay and mixed soil to analyze the thermal characteristics of CLSM(Controlled Low Strength Materials) with accelerated flow ability for various conditions(water content, unit weight, void ratio, curing time) and to evaluate the applicability for backfill material of underground power utilities pipe. The test results of 16 specimens for thermal resistancy test showed good thermal property that maintained below $85^{\circ}C\;cm/W$.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.13 no.3
• /
• pp.233-242
• /
• 2011

This study aims to evaluate the applicability of high-strength concrete mixed with blast furnace slag to shield segment lining in order to improve its performance and economic efficiency. Especially, it was also intended to derive the optimum replacing ratio of ground granulated blast furnace slag to ordinary cement as well as the optimum steam curing condition for shield segment concrete with the design strength of 60 MPa. From a series of experiments, the condition of 50% replacement of ordinary cement by ground granulated blast furnace slag and unit water content of 125 kg/$m^3$ was proposed as the optimum mixing condition. Comparing with standard curing conditions, it was also possible to expect approximately 110~442% strength improvement of concrete by steam curing in the same mixing condition.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.8 no.2
• /
• pp.147-154
• /
• 1988

Korea has the ground which freezes in winter and melts in warmer seasons by turns. Therefore, in designing civil-structures or buildings on such ground, the depth of seasonal frost penetratio must be considered. In this paper, approximate contours of the maximum depth of frost penetration in Korea is presented. It was found that the maximum depth of frost penetration did not have the linear relationship to square root of the freezing index. In order to establish more reliable method to estimate the maximum depth of frost penetration, a new empirical equation is introduced. In the presented equation, the dry unit weight and water content of soil are considered in addition to the freezing index. And the equation is compared with other previous equations used so far.

• Asian-Australasian Journal of Animal Sciences
• /
• v.33 no.8
• /
• pp.1252-1264
• /
• 2020

Objective: To effectively utilize crop by-product resources to address the shortage of animal feed during the dry season in Africa, the community of natural lactic acid bacteria (LAB) of corn stover and sugarcane tops and fermentation characteristics of silage were studied in Mozambique. Methods: Corn stover and sugarcane tops were obtained from agricultural field in Mozambique. Silage was prepared with LAB inoculant and cellulase enzyme and their fermentation quality and microbial population were analyzed. Results: Aerobic bacteria were the dominant population with 10⁷ colony-forming unit/g of fresh matter in both crops prior to ensiling, while 10⁴ to 10⁷ LAB became the dominant bacteria during ensiling. Lactobacillus plantarum was more than 76.30% of total isolates which dominated silage fermentation in the LAB-treated sugarcane top silages or all corn stover silages. Fresh corn stover and sugarcane tops contain 65.05% to 76.10% neutral detergent fiber (NDF) and 6.52% to 6.77% crude protein (CP) on a dry matter basis, and these nutrients did not change greatly during ensiling. Corn stover exhibits higher LAB counts and water-soluble carbohydrates content than sugarcane top, which are naturally suited for ensiling. Meanwhile, sugarcane tops require LAB or cellulase additives for high quality of silage making. Conclusion: This study confirms that both crop by-products contain certain nutrients of CP and NDF that could be well-preserved in silage, and that they are potential roughage resources that could cover livestock feed shortages during the dry season in Africa.

• Journal of the Korean Geotechnical Society
• /
• v.20 no.1
• /
• pp.131-139
• /
• 2004

When calculating bearing capacity and settlement of actual foundation from plate test result fur design and construction of shallow foundation, scale effect should be considered. But, adequate guide and test result of scale effect were not prepared yet in Korea. So, to analyze the relations of bearing capacity and settlement as the difference of loading plate sizes, model test and field loading test were performed with different loading plate on weathered-granite layer. Model tests were conducted with water content, compaction number, saturated unit weight and plate size(Dl5, 25cm) in soil-box$(2,000\times 2,000\times 1,000mm)$ formed soil layer. Field loading tests were carried out with diameters of loading plate$(D15, 25, 30, 40, 75\times 75, 140\times 210cm)$ on the same soil condition. Finally, we presented the prediction formula of bearing and settlement for computating scale offset in design of shallow foundation through result analysis of load test and numerical simulation on weathered soil and rock.

• Food Engineering Progress
• /
• v.13 no.3
• /
• pp.216-220
• /
• 2009

The several functional properties of freeze-dried powder of Aloe vera gel was examined as influenced by pre-concentration degrees of the gel solution. As a pre-treatment prior to freeze drying, the gel solution was vacuum-concentrated by three levels (unit: g-water/g-solids) - high (H), 76; medium (M), 119; low (L), 159. In FT-IR spectra, the sample H showed the highest absorbance in the range of 1600-1550 $cm^{-1}$ and 1450-1400 $cm^{-1}$, which corresponded to level of the acetyl group in glucomannan. The sample H of freeze-dried powder was the highest in polysaccharide content, jack bean urease inhibition rate, and FAC (fat adsorption capacity). It could be inferred that the sample H had an effect on Helicobacter pylori inhibition and fat adsorption suppression according to urease inhibition rate and FAC, respectively.