• Proceedings of the Korean Institute of Building Construction Conference
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• 2015.11a
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• pp.103-104
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• 2015

This study is an experiment about what affects the compressive strength by using a reducing agent (PNS based admixtures) to play cement using the cement paste based Waste Concrete Powder of waste concrete, which accounts for more than 60% of construction waste around the latest domestic and international It was. Securing the replacement of cement with Waste Concrete Powder and, by varying the admixture was to compensate for the low absorption of liquidity and obtain a fine powder. And the experiment was conducted with a constant water cement ratio and aggregate usage for the purpose of lowering the water cement ratio promoting strength development. When substituted with the experimental results of 0.3% based on 3 ~ 28 days as strength 36Mpa exhibited the highest strength.

• Journal of the Korean Ceramic Society
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• v.36 no.2
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• pp.130-135
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• 1999

The enhanced slag fineness and the batch water of low water-to-cement ratio(W/C) were employed in order to improve the early strength of blast-furnace slag blended cement at low temperature. A grinding aid was used to grind the blast-furnace slag into the fineness of 6,280$\textrm{cm}^2$/g (Blaine), and this fine slag was then homogeneously mixed with the ordinary Portland cement to produce the blast-furnace slag blended cement containing 40% slag by weight composition. On the other hand, the batch water could be reduced from W/C=0.50 (KS L 5105) to W/C=0.33 through a commercial, naphthalene type superplasticizer. Through the method mentioned above, the early strength of the blast-furnace slag blended cement at low temperature could be enhanced even somewhat higher than the Portland cement strength. And the microsturcture of the cement was studied by both the pore structure analysis and the A.C. impedance measurement.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.61-64
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• 1997

As construction technology advances, most of concrete structures are becoming larger and taller. Therefore, high strength and quality concrete is necessary for them. So, the proposal of using belite cement is investigated to satisfy high flowing, low heat, and high strength. In this study, the compressive strength, tensile strength, and modulous of elasticity of concrete using belite cement was considered according to the mix proposition condition as a water-cement ratio, unit cement content, and sand percentage.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.919-924
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• 2001

The purpose of this study is to prepare the basic data for the development of building board with expanded perlite. Each paste was mixed with four levels of water cement ratio(30, 40, 50, 60%), and expanded perlite was substituted with four levels of substitutive ratio(20, 40, 60, 80%) for the each paste. The physical property, compressive strength, bending strength and thermal conductivity of each cement composite which is made through previously described method were analyzed and the result was as follow. In the case of 80 percent substitutive ratio, the cement composite had a mechanical defect which was resulted from lack of paste content. In the case of 40 and 60percent substitutive ratio, the cement composite had sufficient strength, light weight and low thermal conductivity for application to fire resisting board.

• Journal of Environmental Science International
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• v.26 no.11
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• pp.1267-1274
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• 2017

A Controlled Low-Strength Materials (CLSM) is suitable for mine backfilling because it does not require compaction owing to it high fluidity and can be installed quickly. Therefore, a CLSM utilizing $CO_2$-solidified Circulating Fluidzed Bed Combustion (CFBC) coal ash was developed and it's properties were investigated, since. $CO_2$-solidification of CFBC coal ash can inhibit exudation of heavy metals. The chemical composition and specific surface area of Pulverized coal Combustion fly ash and CFBC fly ash were analyzed. The water ratio, compressive strength and length change ratio of CLSM were confirmed. The water ratios differed with the specific surface area of the CLSM. It was confirmed that the porosity of CLSM affected its compressive strength and length change ratio.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2018.11a
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• pp.46-47
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• 2018

High performance concrete with low water-to-cement ratio has been widely used with increased demand of high rising buildings and huge scaled structures. Additionally, for high performance concrete, various SCMs are replaced to improve its performance from fresh state to hardened state. With the drawback of increased viscosity of the concrete mixture for high performance concrete, low-viscosity typed high range water reducer is the relatively new admixture. Therefore, as a goal of the research, under using various SCMs with wide range of content, the performance of low-viscosity typed high range water reducer was evaluated. Especially, in this research, the influence of low-viscosity typed high range water reducer on rheological properties including plastic viscosity and yield stress were assessed. As a result of the research, it is expected to provide a fundamental information of low -viscosity typed high ranged water reducer on high performance concrete with various conditions of SCMs.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 1996.06c
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• pp.212-218
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• 1996

The concrete pipe used to distribute irrigation water to the right place now available is commonly made up of cement , sand, earth, pebble, etc. These materials with right ratio and right amount of water were mixed and squeezed through the pipe-making machine called vertical squeezed pipe-making machine, and then a cement prefabricated pipe is produced . This kinds of pipe has been expanding by leaps and bounds. Being little cement contents and low cost, the length of pipe is 1.0m or so with weight of 50kg, which is easy to be made and to be transported. The demolish pressure of it is 0.2 MPa or so, which meets the needs of agriculture irrigation . The buried pipe irrigation system, has been popularized in Jining Municipal , Shandong Province. By the year of 1995 , the irrigation area under pipe conveyancesystem usign this type of pipe has reached 74000 hectares. By calculation, about 27.7million ㎥ water, 2.88 million kWh power , 0.167 million man power and 1528 hectares cu tivated land will be saved one year, adding value of agriculture output increased by 10 million kg. The total economic benefits amount to 0.92 million US$ a year. The paper presents the pipe making course and its application on a large scale area.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5C
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• pp.207-215
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• 2009

Cemented soils or concrete are usually cured under moisture conditions and their strength increases with curing time. An insufficient supply of water to cemented soils can contribute to hydration process during curing, which results in the variation of bonding strength of cemented soils. In this study, by the consideration of in situ water supply conditions, cemented sand with cement ratio less than 20% is prepared by air dry, wrapped, moisture, and underwater conditions. A series of unconfined compression tests are carried out to evaluate the effect of curing conditions on the strength of cemented soils. The strength of air dry curing specimen is higher than those of moisture and wrapped cured specimens when cement ratio is less than 10%, whereas it is lower when cement ratio is greater than 10%. Regardless of cement ratio, air dry cured specimens are stronger than underwater cured specimens. A strength increase ratio with cement ratio is calculated based on the strength of 4% cemented specimen. The strength increase ratio of air dry cured specimen is lowest and that of wrapped, moisture, and underwater cured ones increased by square. Strength of air dry cured specimen drops to maximum 30% after wetting when cement ratio is low. However, regardless of cement ratio, strength of moisture and wrapped specimens drops to an average 10% after wetting. The results of this study can predict the strength variation of cemented sand depending on water supply conditions and wetting in the field, which can guarantee the safety of geotechnical structures such as dam.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.79-84
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• 2001

Because the WFS(Waste Foundry Sand), by-product of a casting factory, is generally a smaller particle than a fine aggregate, it has a bad influence on quality of concrete. Especially, the grading of aggregate is a very important factor in the case of concrete-based products having low water cement ratio manufactured by vibration and pressing method. Therefore, it is necessary to use WFS with the suitable grading of aggregate that it don't has a bad Influence on the quality of concrete-based products. This study investigated the suitable using proportion of WFS by means of the composition method of aggregate suggested by Driscoll. The results showed that it was desirable to use 10% of WFS since higher strength was developed with that amount.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.985-990
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• 2001

Chloride permeability of high strength concrete(HSC) was investigated using saltwater pending test and rapid chloride permeability test by electrical potential(ASTM C 1202). The lower water-cement ratio concrete showed the lower diffusion coefficient of chloride. The relationship between the diffusion coefficient of chloride and charge passed by the rapid chloride permeability test could be obtained. This relationship appears to be an effective method for evaluating chloride permeability of low water-cement HSC.