• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.1
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• pp.1-7
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• 2020

GGBFS(Ground Granulated Blast Furnace Slag) is one of the most actively used mineral admixtures with excellent long-aged strength and chloride diffusion resistance. Unlike Standard covering GGBFS in Japan and the U.K., the domestic standard for GGBFS does not contain low fineness of GGBFS under 4000 grade. In this paper, several basic tests are carried out for the concrete with 3,000 grade GGBFS concrete and ternary blended concrete for reducing hydration heat by mixing 4,000 grade GGBFS and fly ash, such as fresh concrete properties, compressive strength, and shrinkage properties. The air content and slump between the ternary blended concrete and the concrete with low-fineness GGBFS showed the similar level, and the results of difference in setting time from them were less than 20 minutes, showing no significant difference. In the evaluation of compressive strength and shrinkage characteristics, the ternary blended concrete showed lower long-aged strength and higher shrinkage than the low-fineness GGBFS concrete.

• Journal of the Korea Institute of Building Construction
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• v.18 no.6
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• pp.551-558
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• 2018

This study evaluate the fluidity and hardening properties of mortar by replacement ratio of ferronickel slag powder to estimate the applicability of ferronickel slag powder for cement replacement materials. Ferronickel slag powder was replaced by 0, 5, 10, 15 and 20% of the cement weight. In addition, blast furnace slag powder and fly ash were also used for comparing with the mixtures using ferronickel slag powder. As the test results, the micro-hydration heat of the mixture containing the ferronickel slag powder was lower than that of the mixtures containing the same amount of blast furnace slag powder and fly ash. The flow of the sample with ferronickel slag powder was relatively higher than the other mixtures. In all ages, the compressive strength of the mixture with ferronickel slag powder and fly ash was similar to that of the mix containing only fly ash. In case of drying shrinkage, the mixture containing ferronickel slag powder exhibited lower drying shrinkage than the mixture using blast furnace slag powder, and similar to the mixture containing fly ash.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.3
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• pp.292-303
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• 2002

This paper presents experimental results for early-age properties of concrete such as the setting time and strength, evaluated via the ultrasonic pulse velocity (UPV). Developing and using an automatically-recording monitoring system, the UPV's of mortar and concrete with various water to binder ratios (W/B) were measured during the first 24 hours. In addition, probe penetration and compression tests were conducted to measure the setting time and compressive strength, respectively. It was observed that the UPV's of mortar with high W/B remained constant during the first 6.5 hours and then abruptly began to increase at constant rates. On the other hand, the UPV of mortar with low W/B increased relatively slowly and gradually due to the setting retardation caused by the use of high range water reducing agent (HRWR). It was found that setting of concrete occurs when the UPV reaches a certain value. Moreover, it was concluded that the estimation formulas should incorporate the effects of W/B to more accurately estimate the early-age strength of concrete from the UPV.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.562-570
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• 2020

This study explores manufacturing technology and basic properties of high strength cement composites at 2,000kg/㎥ of specific weight. It is suggested that lightweight-high strength cement composites can be produced by substituting silica sand in ulta-high performance concrete mixture with lightweight materials such as solid bubbles and lightweight fine aggregates. The 28-day compressive strengths of cement composites with solid bubbles were from 116MPa to 141MPa at below 2.0g/㎤ of unit density while the cement composites with lightweight aggregates possessed lower compressive strength and higher unit density. The specific weight calculated from mixture proportions did not have significant difference with unit density of hardened cement composites, indicating that unit density of hardened cement composites can be estimated from the specific weight in mixture proportions.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.4
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• pp.96-102
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• 2019

When GGBFS(Ground Granulated Blast Furnace Slag) with high blaine is incorporated in concrete, compressive strength in the initial period is improved, but several engineering problems arise such as heat of hydration and quality control. In this paper, compressive strength and durability performance of concrete with 3,000 Grade-low fineness slag are evaluated. Three conditions of concrete mixtures are considered considering workability, and the related durability tests are performed. Although the strength of concrete with 3,000 Grade slag is slightly lower than the OPC(Ordinary Portland Cement) concrete at the age of 28 days, but insignificant difference is observed in long-term compressive strength due to latent hydration activity. The durability performances in concrete with low fineness slag show that the resistances to carbonation and freezing/thawing action are slightly higher than those of concrete with high fineness slag, since reduced unit water content is considered in 3,000 Grade slag mixture. For the long-term age, the chloride diffusion coefficient of the 3000-grade slag mixture is reduced to 20% compared to the OPC mixture, and the excellent chloride resistance are evaluated. Compared with concrete with OPC and high fineness GGBFS, concrete with lower fineness GGBFS can keep reasonable workability and durability performance with reduced water content.

• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.1
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• pp.89-96
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• 2022

In this paper, to evaluate the output quality of the cementitious composite mixture for printing with the ME method for construction 3D printer, visual inspection of the output appearance and the dimensional error rate, compressive strength and flexural strength of the output were measured. As a result of the test, the mixing design with excellent output appearance was P1-2, P1-4, P2-5, P2-6, and the mixing design with good output appearance was P0-1, P1-1, P1-3, P1-6, P1-7 and P2-4. Of these mixing designs, P0-1 and P2-6 had the lowest dimensional error rates As a result of evaluating the compressive strength and flexural strength of the various mixing designs, the Mixing design with excellent output designs showed good mechnical properties. However, mixing designs with excellent mechanical properties does not necessarily have excellent output quality. Therefore, in order to accurately evaluate the output quality, it is judged that visual inspection and dimensional error rate inspection should be performed first, and then the mechanical characteristics should be reviewed.

• Journal of the Korean GEO-environmental Society
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• v.25 no.6
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• pp.5-12
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• 2024

Currently, a grouting method that minimizes damage to the reservoir embankment by injecting solidification agent at low pressure is commonly used to ensure waterproofing and safety of the embankment, but the use of solidification agents can cause issues, such as a decrease in durability and a lack of clear method for determining the mixing ratio. In this study, when the base ground and solidification agent were stirred and mixed at various weight mixing ratios, the permeability coefficient and strength of the mixture were confirmed through laboratory tests, and the optimal mixing ratio was suggested through analysis of the test results. The specimen for the laboratory test was produced considering the mixing ratio of the solidification agent. The specimen for the permeability coefficient test was tested by producing one each of cohesionless and cohesive soil for a mixing amount of 1.5 kN/m³ of solidification agent, and the permeability test results confirmed that the water barrier performance was secured below the permeability coefficient value required by various design criteria. A total of 24 specimens for the strength test were produced, 3 for each of 5 mixing amounts for cohesive soil and 3 mixing amounts for cohesionless soil. The strength test results showed that the uniaxial compressive strength tends to increase linearly with increasing curing time for both cohesionless soil and cohesive soil when the mixing amount is less than 2.0 kN/m³. Therefore, the optimal mixing ratio applied to the site is determined to be mixing amount of 1.5 kN/m³ and 2.0 kN/m³. Finally, numerical analysis reflecting test results was conducted on design case for improvement projects for aging reservoirs embankment to verify the water barrier performance and safety improvement effects.

• Magazine of the Korea Concrete Institute
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• v.4 no.2
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• pp.83-92
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• 1992

본 연구의 목적은 현장에서 구입 가능한 저품질의 재료를 사용한 일련의 실험을 통하여 28일 압축강도와 물\ulcorner시멘트비와 관계를 유출함으로써 고강도 콘크리트의 배합설계식을 얻기 위한 것이다. 목표슬럼프는 고층건물에서의 시공성을 고려하여 15$\pm$2cm로 하였으며 혼화제로는 고성능감수제를 사용하였다. 실험결과로부터 고강도콘크리트의 응력-변형도 특성을 비롯하여 탄성계수, 포아송비, 단위중량 등 고강도 콘크리트의 일반적인 재료성질을 얻었으며 본 연구에서 제안한 고강도콘크리트의 배합설계식은 국내현장조건을 고려한 실용식으로 고강도콘크리트으 설계 및 시공을 위한 기초자료로 사용 가능하다고 판단된다.

• Magazine of the Korea Concrete Institute
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• v.9 no.2
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• pp.145-151
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• 1997

In concrete mix design we need the informations of the codes, the specifications, and the experiences of experts. However we can't consider all factors regarding concrete mix design. The final acceptance depends on concrete quality control test results. In this process we meet the uncertainties of materials. temperature, site environmental situations, personal skillfulness. and errors in calculations and testing process. Then the mix design adjustments must be made. Concrete mix design and adjustments arc somewhat complicated, time-consuming. and uncertain tasks. In this paper, as a tool to minimize the uncertainties and errors the neural network is applied to the concrete mix design. Input data to train and test the neural network are obtained numerically from the results of design following the concrete standard specifications of Korea. The 28-days compressive strengths which are variate according to the uncertainties and errors are considered. The results show that neural networks have a strong potential as a tool for concrete mix design.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2001.11a
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• pp.370-374
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• 2001

기존의 다른 폐자재와는 달리 탄소배합 콘크리트는 탄소는 그 자체가 물을 흡수하는 성질이 있어 배합콘크리트에 밀실하게 배합되기가 쉽지 않으나 일단 밀실하게 제작되면 압축강도가 크게 개선되는 것으로 전기$\cdot$전도에 큰 성능개선을 할 수 있는 것으로 보여 진다