• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.451-459
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• 2021

The purpose of this study is to evaluate the performance of a solidifying agent for recycling the fine powder separated from the nuclear power plant decommissioned concrete as a solidifying agent(SA) for radioactive waste. In order to evaluate the performance of the solidifying agent, a powder simulating the fine powder of waste concrete separated from the dismantled concrete of a nuclear power plant was produced, and the main variables were the type of binder and the replacement ratio of zeolite. The solidifying agent was evaluated for fluidity performance, compressive strength, and leaching resistance to non-radioactive cesium. The compressive strength of SA increased as the zeolite replacement ratio increased, and the SA containing 5% or more of zeolite showed a compressive strength that was 1.4 to 1.7 times higher than the acceptance criteria. The cesium leaching index of all specimens was 6 or higher, satisfying the acceptance criteria, and the leaching index of SA was 1.47~1.63 times higher than that of OPC. In particular, the average leaching index after 28 days of the 5% zeolite-substituted solidifying agent was 9.15, which was improved by about 6.4% compared to OPC, and it was confirmed that the zeolite was effective in improving the leaching resistance to cesium ions by showing stable performance over the entire period.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.609-612
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• 2006

The quality of the concrete compression strength can be determined after the passage of 28 days, but if any defect is found the quality of concrete after that length of time, there can be serious problems in dismantling and repair. Thus, in response to the use of concrete using non sintering cement (NSC), the present study purposed to propose a method of managing the strength of high strength concrete using NSC in comparison with high strength concrete using ordinary Portland cement (OPC) through early strength estimation using microwave, which enables the quick estimation of the strength of high strength concrete using NSC.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.329-332
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• 2004

This study aims to manufacture non-sintering cement(NSC) by adding phosphogypsum(PG) and waste lime(WL) to granulated blast furnace slag(GBFS) as sulfate and alkali activators. This study also investigates the pore structure of NSC Matrix. The result of experiment of pore structure properties, showed no considerable difference for total pore volume by cement mixing ratio but shows a large distinction in distribution of pore diameter. On the whole, pore-diameter of paste of NSC show that occupation ratio of pore diameter below 10mm is larger and is smaller than OPC and BFSC at pore diameter of over 10nm. Such a reason is that the hydrate like CSH gel and ettringite formed dense pore structure of NSC matrix.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.725-728
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• 2006

This research investigates the characteristics of chloride fixation in non-sintering cement(NSC) matrix. NSC was manufactured by adding phosphogypsum and slack lime to granulated blast furnace slag as sulfate and alkali activators. As a result, the concentration of chloride ion in pore solution of NSC-solidified matrix is more low than that of OPC-solidified matrix containing the same chloride content in cement paste. Also, the concentration of chloride ion in pore solution of NSC-solidified matrix is similar with that of BSC-solidified matrix containing the same chloride content in cement paste.

• Journal of Ceramic Processing Research
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• v.19 no.6
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• pp.509-513
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• 2018

This study uses fly ash for non-shrinkage grout in order to develop strength of grout and improve its durability. We grind fly ash to the extent of $7,000cm^2/g$ and use ground fly ash and raw fly ash respectively at the proportion of 10%, 20%, 30% instead of OPC and compare the results drawn on the condition of each proportion. As a mixed material of grout, EVA and water-reducing agent is added in order to prevent bleeding and improve segregation resistance, CSA is added with a view to preventing drying shrinkage and improving early strength property. In regard to flow and flow time test for analyzing and evaluating workability, it is revealed that grouts of all mix proportions except raw fly ash 30% mix proportion satisfy all performance criteria. With regard to length change rate, grout with no admixture shows the highest shrinkage rate, but the rate is 0.0005%, extremely insignificant rate. As material age increases, compressive strength of two grouts, that is to say ground fly ash 10% and 20%-used grouts, exceed that of grout with no admixture or show high-level compressive strength.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.297-298
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• 2023

In the concrete industry, efforts are being made to reduce CO₂ emissions, and technologies that collect, store, and utilize CO₂ have recently been studied. This study analyzed the change in compressive strength after the accelerated carbonation test of Non-Sintered Cement(NSC) mortar. Type C Fly Ash and Type F Fly Ash were mixed in a 1:1 ratio and then mixed with Blast Furnace Slag fine powder to produce NSC. The mortar produced was cured underwater until the target age. In addition, an accelerated carbonation test was conducted under the condition of a concentration of 5 (±1.0%) of CO₂ gas for 14 days. The mortar compressive strength was measured before and after 14 days of accelerated carbonation test based on the 7th and 28th days of age. As a result of the experiment, the compressive strength was improved in all binder. In general, the compressive strength of NSC mortar subjected to the accelerated carbonation test was similar to that of Ordinary Portland Cement(OPC) mortar not subjected to the accelerated carbonation test.

• Journal of the Korean Institute of Rural Architecture
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• v.22 no.3
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• pp.17-24
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• 2020

Reservoirs, which make up most of South Korea's reservoirs, are located in rural areas. In the case of rural reservoirs, about 75% have been reported over 50 years old aged reservoirs constructed before the 1960s. Reservoirs are important facilities that store and supply water necessary for daily life. However, if it is destroyed, the reservoir can cause a lot of damage, so continuous management is necessary. As a method for strengthening old reservoirs, a method using cement has been widely applied. However, OPC is a product that uses a lot of carbon dioxide and natural resources. Therefore, the amount of cement should be reduced. Against this background, in this study, the ground injection material of utilizing circulation resources was applied to the site. Applied reservoirs have been around for 75 years and leaks have occurred in some sections. The application method was constructed in two rows, up to a depth of 12m. After reinforcement, the electrical resistivity test was conducted three times. As a result, similar resistance was shown at 1 month after construction. And after 6 months, the saturation area decreased. And the performance after reinforcing the aged reservoir was examined. As a result of the review, this study confirmed that the applicability was equivalent to that of OPC, and the excellent performance of reinforcing the aged reservoir was shown.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.673-676
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• 2008

Color concrete utilizes peculiar texture and color sense in external appearance actively as a finish. But, this color concrete is essential use of pigment for required color revelation, and color cone cleat from mixing of this pigment are different existent achromatic color concrete and basic properties of matter. this study progressed slump test and setting time examination through mortar injection resistance examination of mortar that mix Pigment.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.521-528
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• 2021

The high-density fiber composite manufacturing method by the extrusion molding method has the characteristic that continuous production is possible, and the product is molded through a mold forming a specific cross-section. OPC is used as a defect material, an appropriate amount of SiO₂ is supplied for CaO reaction activity, and high density and high strength are expressed through steam and autoclave curing. However, due to the use of organic reinforcing fibers, the flame duration exceeds the regulations during the non-combustible performance test, making it difficult to secure performance. In this study, the product was produced by mixing alkali-resistant organic fiber and fly ash having voids as a binder by replacing the existing polypropylene fiber. appeared to be possible.

• Computers and Concrete
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• v.22 no.3
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• pp.319-326
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• 2018

RC (Reinforced Concrete) members are always subjected to loading conditions and have construction joints when constructed on a big scale. Service life for RC structure exposed to chloride attack is usually estimated through chloride diffusion test in sound concrete, however the test is performed without consideration of effect of loading and joint. In the present work, chloride diffusion coefficient is measured in concrete cured for 1 year. In order to evaluate the effect of applied load, cold joint, and mineral admixtures, OPC (Ordinary Portland Cement) and 40%-replaced GGBFS (Ground Granulated Blast Furnace Slag) concrete are prepared. The diffusion test is performed under loading conditions for concrete containing cold joint. Investigating the previous test results for 91 days-cured condition and the present work, changing diffusion coefficients with applied stress are normalized considering material type and cold joint. For evaluation of service life in RC continuous beam with 2 spans, non-linear analytical model is adopted, and service life in each location is evaluated considering the effects of applied stress, cold joint, and GGBFS. From the work, varying service life is simulated under various loading conditions, and the reduced results due to cold joint and tensile zone are quantitatively evaluated. The effect of various conditions on diffusion can provide more quantitative evaluation of chloride behavior and the related service life.