• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.759-764
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• 2004

In this study, the experiment was carried out to investigate and analyze the ready-mixed concrete production of ultra-high strength concrete with mixing strength of $100N/mm^2$ according to types of mineral admixtures. The main experimental variables were water/binder ratio $25.0\%$, water content $160kg/m^3$ and mineral admixtures such as fly ash, silica fume and meta kaolin. According to the test results, the principle conclusions are summarized as follows. 1) even if it secures similar slump, the viscosity appear to difference by mixing condition relatively. 2) The autogeneous shrinkage of ultra-high strength concrete is profitable that use admixture, and heat of hydration is desirable that apply considering countermeasure enough in the advance. 3) The concrete that use SF10+MK10 on 56days could confirm that it is possible that achieve compressive strength more than $100N/mm^2$ under mixing conditions that is appearing by compressive strength $102.7N/mm^2$.

• Journal of Industrial Technology
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• v.24 no.A
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• pp.17-22
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• 2004

In the study, we have developed a straightening system for 304 micro wires that are normally used in the medical and semi-conductor fields. To apply heat to the micro wires, we introduced the direct wire heating method which generates the thermal energy by the electrical resistance of the wire itself. To avoid the deterioration of the wire surface by the environment, such as the oxidation or the hydration, the $N_2$ gas was filled in the glass pipe in which the straightening process was being performed. A precision tension meter was also attached to control the tension of the wire during the heating and straightening process. In order to control the straightening process, several experimental investigations with varying the tension, the feeding velocity and the temperature (current) was carried out. As a result of experiments, we obtained the optimal processing conditions satisfying the straightness requirement of the micro wires.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.159-160
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• 2009

The application of 40MPa high strength concrete was accepted as a goal for improving durability and reducing column's section in concrete bridge piers. As a result of applying 40MPa high strength concrete, it could be achieved that column diameter and coping height were reduced into 0.6m, 0.4m, respectively. And crack by heat evolution of hydration did not generate, because of a careful quality and curing control of high strength concrete.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.4
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• pp.195-202
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• 2004

In this study, it was founded to make the optimal mixture for producing concrete which is self-compacting, yet, and generates low heat of hydration by using flyash, blast furnace slags and limestone powders as binders in addition to cement while using super-plasticizers and viscosity agents as admixture agents. The structural behaviors of the concrete produced with the selected mixture were compared with those of the concrete currently using for construction of nuclear power plants. The study shows that the blended high fluidity concrete including limestone is better in workability and durability than the concrete currently in use for nuclear power plants.

• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.349-356
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• 2002

This research deals with the properties of fresh and hardened high-performance concrete(HPC) incorporating high-reactivity metakaolin(HRM). The properties of fresh and hardened state concrete were investigated included air content, slump flow, setting time, heat of hydration, compressive strength, resistance to chloride-ion penetration, abrasion and repeated freezing and thawing. The properties of the HRM concrete were also compared with those of the portland cement concrete and silica fume(SF) concrete. The laboratory test results indicate that HRM material can be used as a supplementary cementitious material to produce high-performance concrete.

• Journal of the Korean Ceramic Society
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• v.32 no.10
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• pp.1147-1161
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• 1995

When ceramic membrance was made from metal salt solution in place of metal akoxide solution, crack free and good adhesion to supporter was optimized for sol stability and good adhesion force. A starting sol was prepared from aluminum oxychloride aqueous solutjion in order to inhibit the grain growthof Al2O3 during heat treatment. The crack free dip coating can't be achieved in 1mol/ι zirconium oxychloride solution because of the high viscosity which interferes with the hydration copolymerization between Al3+ ion and Zr4+ ion. Thus Al2O3-ZrO2 sol stability and viscosity for dip coating was effective when 0.01 mol/ι zirconium oxychloride was added. The minimizing of crack and achieving better adhesion to the supporter wa obtained by microwave drying, surfactant addition and ultrasonic dip coating in wet atmosphere. The result seems to minimize the capillary force and improve the adhesive ability to supporter during the process. Where the average pore size of Al2O3-ZrO2 ultrafilter ceramic membrane measured 17 Å by the BET method and observed γ-Al2O3 phase with tetragonal zirconia after firing at 700℃.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.06a
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• pp.206-207
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• 2020

Accurate estimation of concrete strength development at early ages is a critical factor to secure structural stability as well as to speed up the construction process. The temperature generated from the heat of hydration is considered as a key parameter in predicting the early age strength. Conventionally, concrete temperature has been measured by temperature sensors installed inside concrete. However, considering the measurement on building structures with multiple floors, this method requires reinstallation and repositioning of hardware such as sensors, data loggers and routers for data transfer. This makes the temperature monitoring work cumbersome and inefficient. Concrete temperature monitoring by using thermal remote sensing can be an effective alternative to supplement those shortcomings. In this study, image processing was carried out through K-means clustering technique, which is a unsupervised learning method, and the classification results were analyzed accordingly. In the future, research will be conducted on how to automatically recognize concrete among various objects by using deep learning techniques.

• The Journal of the Korea Contents Association
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• v.12 no.8
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• pp.366-372
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• 2012

In most of construction work, especially mat foundation construction, it is very important that accidents be prevented at early aged construction stage. To reduce the risk of accidents, it is necessary to choose the curing method to provide instructions for safety forming work by proper curing of concrete after placing. Therefore, this paper has proposed a designation algorithm of curing method for representing curing type and period by analyzing the transient hydration heat solution, focusing on mat foundation construction. This has been implemented, moreover, using an object oriented programming language to develop structural analysis system taking account crack index. In addition, we present in this paper a safety curing management system developed to assess risk during forming work.

• Magazine of the Korea Concrete Institute
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• v.10 no.5
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• pp.89-100
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• 1998

본 연구는 양생온도이력이 콘크리트 강도에미치는 영향을 평가하기 위한 것으로 물 시멘트비가 60%, 45%, 26%인 3종류의 콘크리트에대하여 5$^{\circ}C$부터 5$0^{\circ}C$까지의 항온양생과 초기재령에 고온도이력을 변수로 한 변동온도양생을 실시한 공시체의 압축강도를 측정하였다. 또한 그 실험결과에 강도평가 방법의 하나인 Maturity 개념을 도입하여 강도평가에 미치는 재령, w/c, 온도이력 등에 대한 영향을 평가하였다. 항온양생 실험결과에 따르면 물시멘트비가 낮을수록 초기재령에서의 강도발현은 높게 나타나며 양생온도 5$0^{\circ}C$인 경우를 제외하고 재령7일까지의 강도발현은 양생온도가 높을수록 크게 나타나고 있다. 한편, 변동온도양생실험결과에 의하면 초기재령에서 고온양생한 콘크리트의 강도발현은 물시멘트비의 영향을 크게 받으며, 1주 이후의 양생온도가 강도발현에 미치는 영향은 1주까지의 고온도이력에 대한 영향에 비교해 2차적이다. 기존의 Maturity개념인 Saul-Bergstrom의 함수와 Ooi의 함수를 가지고 항온 및 변동온도 양생실험결과를 분석한 결과, 전체적으로 Saul-Bergstrom식에 의한 경우가 실험값과의 차이가 작게 나타났으나 두 식 모두 Maturity 가 큰 경우에는 계산에 의한 값이 실험에 의한 값보다 크게 나타나고 있어 장기 재령시 강도평가는 한계강도 개념을 고려한 새로운 Matruity함수를 제안할 필요가 있다.

• Journal of the Korea Concrete Institute
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• v.20 no.6
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• pp.797-807
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• 2008

For this study, the semi-adiabatic temperature rising test is accomplished by using ternary system cement (OPC, BFS, FA) reducing temperature crack. Two tests are conducted; one is for the paste test, and the other is for the concrete test. As the results of paste tests, using fly ash is better to reduce hydration temperature than doing blast furnace slag. In the case of the paste mixed ternary system cement, the more fly ash is mixed and the less blast furnace slag is used, the lower the temperature is. The less the mixture ratio of blast furnace slag is and the more the mixture ratio of fly ash is, the later the temperature rising velocity and descending velocity are. Besides, the temperature is lower if water/binder ratio is high. The use of ternary system cement has the retardation effect of temperature rising because the time to reach the maximum temperature is in the order of OPC100, binary system cement, and ternary system cement. From the test, the maximum temperature of concrete used ternary system cement is $8{\sim}11^{\circ}C$ lower than that of concrete used OPC100. Moreover, temperatures rising velocity and descending velocity of ternary system cement range $47{\sim}51%$ and $37{\sim}42%$ compared with OPC100. The specimen of concrete shows remarkable low internal temperature and slow temperature rising velocity and descending velocity compared with the specimen of paste because it is that temperature loss of concrete is much more than paste specimen according to aggregates.