• Magazine of the Korean Society of Agricultural Engineers
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• v.26 no.3
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• pp.68-80
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• 1984

This study was attempted in order to investigate the effects of superplasticizers on fresh and hardened concrete. The experimental program included tests on the slump and slump loss, bleeding, time of set, air content, the compacting, factor Vee Dee, compressive strength, tensile and flexural strength, permeability, shrinkage and freege-thaw durability. The major conclusions that can be drawn on the study are as follows. 1. Superplasticizers were observed to have an appreciable fluidifying action in fresh concrete so that tinder appropriate conditions, they either considerably improved its workability or permitted a water reduction of at least 8-12% to be made while maintaining normal workability. 2. The bleeding ratios of base and S,P. Concrete were much lower than those of the conventional concrete. Differences between the base and S.P. Concrete were insignifician. 3. The setting time was the longest for conventionla concrete, followed by S.P. concrete and base concrete in thatorder. And AE water reduction admixtures showed an appreciable influence on the setting and hardening characteristics of concrete and prolonged the stiffening times. 4. The high initial slump values of S.P. concrete generally decreased rapidly with increased standing time. CF values showed increasing tendencies with the increase of S.P. content, and excessive addition of S.P. caused the segregation of fresh concrete, resulting in its rejection. 5. Though there was a slight increase in strength, no significant differences are observed between base and S.P. concrete in terms of the compressive, tensile and flexural strength. 6. The permeability of S.P. concrete was significantly less than that of the conventional concrete, and the shrinkage of S.P. concrete was considerably smaller than that of the conventional concrete, but there were no significant differences between base and S.P. concrete. 7. Compared to base concrete, S.P. concrete without entrained air tended to slightly increase freeze-thaw durability, and S.P. concrete with an appropriate entrained air gave satisfactory resistance to freezing and thawing.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.373-376
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• 2008

The objective of this study is to investigate the properties of fresh concrete with recycled fine aggregates. Three different kinds of fine aggregate with natural, high and low quality recycled aggregates were prepared. The concrete mixtures were produced with test parameters of replacement ratio of recycled fine aggregate. The properties of the fresh concrete were measured by means of slump and air content according to elapsed time. Quality control method to maintain the constant total mixing water for recycled aggregate concrete was suggested. The all concrete mixtures were produced with approximately the same slump on the job site after an hour. Test results indicated that compressive strength of the concrete mixtures with constant slump is not affected by the replacement ratio of recycled fine aggregate. Therefore, the practical way for the quality control of recycled aggregate concrete is to maintain the constant total mixing water.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.10a
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• pp.132-137
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• 1993

The purpose of this study is to evaluate the quality characteristics of concrete using super plasticizer which is on the market within the country. For this purpose, nine kinds of super plasticizer are compared and analyzed for the slump , air content, unit weight, water-reducing percent and ratios of compressive strength with admixture content. As a result, the optimum quantity of admixture content were obtaining for ordinary and high strength concrete using super plasticizer.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.509-512
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• 2006

We have many environmental problems by the polluted materials as a results of mechanical development these days. So people want to use building products made from natural things and take a good effect for people from those bio products. We can instance electron wave shelding, far infrared ray and anion emission, and anti-bacterial property as the latest trend of the bio building material. So we had a experiment to investigate how much bio materials affect concrete when we use in the concrete with cement substitution. We tested slump, 7days compressive strength, and air contents for physical properties of bio concrete. The result is that bio concretes with four bio ingredients have proper values comparing with target values for slump and air content but lower compressive strength than plain concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.174-179
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• 1997

In this study, effects of carbon content and fineness of fly-ash on the workability an the strength development of concrete and investigated experimentally. Carbon content with 6 levels (0, 2, 3, 4, 5, 7%) and fineness with 3 levels (4, 000, 5, 000, 6, 000 $\textrm{cm}^2$/g) are selected for test variables. Besides, the effect of fly-ash with variation of initial concrete temperature is tested. To measure slump and air losses, small laboratory agitator is used. As the results, the used AE admixture content to maintain constant initial air content is increased linearly with increasing carbon content in fly-ash. With increasing fineness of fly-ash, the strengths at 3 and 7 days are slightly increased, however, there is no clear difference among 28 day strengths within the scope of this study.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.631-634
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• 2005

This paper discussed the influence of addition of aqueous additives such as various beverage and detergent on the properties of concrete during placement by workmen's mistake. Slump and air content were not highly affected by the addition of aqueous additives, while addition of detergent led to an remarkable increase in air content due to interfacial activated ingredient in detergent. For setting time, lactic-acid fermented milk exhibited a longest setting delay and in order of coffee and soda. Concrete containing setting retarding beverage had higher compressive strength than control concrete at 7 and 28days. Concrete containing detergent exhibited strength loss due to the presence of larger amount of air content.

• Journal of Industrial Technology
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• v.33 no.A
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• pp.93-99
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• 2013

Shotcrete has been referred to as gunite, pneumatically applied mortar or concrete, sprayed concrete or mortar. There are sound reasons why sprayed mortar is one of the best portland cement based material for repairing old concrete structures. However, it is difficult to find the research results on the latex-modified mortar nevertheless on the impact of air onto the fresh and hardened properties of latex-modified mortar. So, the main experimental program included strength test, slump test, rapid chloride permeability test, image analysis for air void system, and chemical attacks with the main experimental variables of latex content, fine aggregate content, water-cement ratio, and air foamer content.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.11a
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• pp.85-88
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• 2005

This study investigates influence on concrete adding beverage or detergent, by work man's mistakes during concrete placement in field. Overall, concrete adding beverage or detergent does not affect slump and air content, compared with control concrete. However concrete adding detergent resulted in significantly higher air content, due to inter facial activation ingredient. For the properties of setting time, concrete adding lactic acid beverage indicated the longest retarding properties, next was coffee and soft drink in order. Compressive strength of concrete, which retarded setting time. exhibited slightly improved value at 7 and 28 days respectively, while that of concrete adding detergent significantly decreased, due to higher air content.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10c
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• pp.7-12
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• 1998

The waste sludge is by-produced about 20-30% of total production and arised to the severe problems of this mine's surrounding environmnet. This study was invested the composition of component, particle of size of the waste sludge by Chemical Analysis, X, R, D, Particle Size Analyzer and the physical properties (air content, slump, strength, etc) of concrete when the waste sludge is added into concrete. so, It's recomended the proper content of the waste sludge to be added into concrete. and then, is verified to be applied at batch plant in field. Above the results, the recomeded content of the waste sludge is about 2-4% (about 4-8% in cement) in aggregates and when it's added the recomended content, they are detected to be more or less changed the physical properties of concrete, ( equally strength and durability, little less air con tent, little increased shinkage, etc). but the application of the recomended content don't arise the problem of the basic quality control of concrete and physical properties.

• Journal of The Korean Society of Agricultural Engineers
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• v.57 no.2
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• pp.47-56
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• 2015

At the present, the mechanized form roads pavement was constructed with plain concrete. Mostly, it was used by welded wire mesh for preventing crack. Cellulose fibers for the reinforcement of concrete offer relatively high levels of elastic modulus, fiber count (per unit weight), specific surface, and bond strength to cement-based materials. The construction of concrete pavement confirmed that cellulose fiber reinforced concrete was applicable to mechanized form roads pavement. In the study, cellulose fibers were used here at 0.08 % volume fraction, which is equivalent to a fiber content of $1.2kg/m^3$. Cellulose fiber reinforced concrete were compared with plain concrete. Field test results indicated that cellulose fiber reinforced concrete showed slightly to increase of 28 days compressive strength and improved the initial strength. it tended to increase of splitting tensile strength. Test results showed that the slump and air content tend to decreased. but, the variation of air contends is very little. Also, construction cost of cellulose fiber reinforced concrete is less than about 25.7 % the case of welded wire mesh previously used. Therefore, The cost reduction is expected to be possible in construction site by mechanized form roads pavement.