• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.413-416
• /
• 2008

The concrete used most in construction materials. There is an overcrowded iron dimensions use of the concrete at time of the other concrete theory on the reinforcing rod back which did congestion and compares it with this, and there are more few dimensions of the aggregate than concrete, and quantity of aggregate passage is superior in mortar than concrete. If a volume rate of the aggregate writes mortar than concrete against this, therefore, unit amount increases, and quantity of paste increases and quantity of dry shrinkage than increase concrete. However, I let I regulate lay priest distribution of the aggregate, and the results rates increase and reduce unit amount and decrease quantity of dry shrinkage, and separation resistance and the gap passage characteristics are judged because it can be it in a substitute document of very superior concrete. I came to carry out the study that I watched to let I was useful a little more and do the improvement repair of a become building wall body, a basement pillar and repair reinforcement of the assistant in the reinforcing rod back, the old age when I made congestion here. I regulated lay priest distribution of the aggregate in the study and regulated substitution rate of the aggregate (40%, 50%, 60%) and divided W/C 30%, 40% standards and produced mortar and I compared quantity of air by this, slump, compression robbery and showed it this time.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.7 no.4
• /
• pp.287-294
• /
• 2019

GGBFS(Ground Granulated Blast Furnace Slag) has been widely used in concrete for its excellent resistance chloride and chemical attack, however cracks due to hydration heat and dry shrinkage are reported. In many International Standards, GGBFS with low fineness of 3,000 grade is classified for wide commercialization and crack control. In this paper, the mechanical and durability performance of concrete were investigated through two mix proportions; One (BS) has 50% of w/b(water to binder) ratio and 60% replacement ratio with low-fineness GGBFS, and the other (TS) has 50% of w/b and 60% replacement ratio with 4000 grade and FA (Fly Ash). The strength difference between TS and BS concrete was not great from 3 day to 91 day of age, and BS showed excellent performance for chloride diffusion and carbonation resistance. Two mixtures also indicate a high durability index (more than 90.0) for freezing-thawing since they contain sufficient air content. Through improvement of strength in low fineness GGBFS concrete at early age, mass concrete with low hydration heat and high durability can be manufactured.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.4
• /
• pp.111-117
• /
• 2017

This study examined the material properties of Korean rice husk ash (RHA) according to the manufacturing process, and evaluated the feasibility of its use as a new admixture for high strength concrete. For this purpose, its particle size distribution, chemical composition, and microstructure were analyzed under various parameters, such as calcination temperature ($400^{\circ}C$, $650^{\circ}C$, and $900^{\circ}C$) and the inclusion of a milling process. X-ray fluorescence analysis confirmed that the silicon oxide ($SiO_2$) content of RHA was improved to more than 92% with a calcination process at $650^{\circ}C$ or higher. In addition, microstructural analysis showed that the RHA calcined at $650^{\circ}C$ has a porous structure. Because of this, the absorption capacity of the RHA was improved. On the other hand, when the milling process was applied, the porous structure was destroyed; thus, the absorption capacity tended to decrease further. Based on the analysis results, it was concluded that RHA calcined at $650^{\circ}C$ can be used as an admixture for high strength concrete, which possesses functions of both a shrinkage reducing agent and a pozzolanic activator.

• Journal of the Society of Cosmetic Scientists of Korea
• /
• v.41 no.4
• /
• pp.401-411
• /
• 2015

This study was performed to investigate the wound healing effect of skin regeneration cosmetics utilizing low molecular weight Polydeoxynucleotide (PDRN). High purity PDRN was prepared from salmon testes poly-deoxy-ribonucleotide through protein and toxin removal process and molecular weight reduction. In order to evaluate the wound healing effect of PDRN in SD rats, 4 sites of dorsal skin of each animal were excised by using biopsy punch and $500{\mu}L$ of test solution was topically applied once daily for 4 weeks. The tissue changes were observed for every week during the application periods. After applying the PDRN to the wound, the skin was cut flower and contraction of the wounds more quickly, and the coating of PDRN in the wound area was reduced significantly as compared to the positive control group $Fucidin^{(R)}$ applied. The microscopic observation of stained tissue showed that a positive control was most rapid in re-epithelialization ability followed by the PH group, PDRN group, HA group. In addition, transforming growth factor ($TGF-{\beta}$) and vascular endothelial growth factor (VEGF), such as in the growth factor was similar to the results of staining of tissue lesions. In conclusion, it is determined that the low molecular weight PDRN has the therapeutic effect to the wound, and could be used as a functional material of cosmetics and medical industries.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.9
• /
• pp.299-305
• /
• 2019

As the damage factors of the three­storey stone pagoda of the Bulguksa Temple in Gyeongju could cause a reduction in the historical and artistic value and accelerate the deterioration of the stone, an appropriate solution is needed. The aim of stone conservation is to conserve the original shape and convey originality from the ancestors to their descendants. This procedure includes a record of the condition, being available in the future. In particular, the damage assessment could be used in conservational research, educational data, conservational treatment, and preventive data. As a result of quantitative damage assessment, biological damage indicated 159 %, chemical damage 114 %, and physical damage 16 %. The west direction revealed 95 % because of the amount of sunshine, moisture, and expansion of rock. Complex factors and high range damage were observed on the foundation and body of the pagoda. Since the top of pagoda was restored in the 1970s, the state presented a good condition. By doing this, the number of organisms could be reduced by cleaning and the physical damage could be minimized by bonding. On the other hand, continuous monitoring will be needed because there is a possibility of reforming the damage in the future.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.8 no.4
• /
• pp.498-505
• /
• 2020

Aggregate occupies about 70-85% of the concrete volume and is an important factor in reducing the drying shrinkage of concrete. However, when constructing high-rise buildings, it acts as a problem due to the high load of natural aggregates. If the load becomes large during the construction of a high-rise building, creep may occur and the ground may be eroded. Material costs increase and there are financial problems. In order to reduce the load on concrete, we are working to reduce the weight of aggregates. However, artificial lightweight aggregates affect the interface between the aggregate and the paste due to its higher absorption rate and lower adhesion strength than natural aggregates, affecting the overall strength of concrete. Therefore, in this study, in order to grasp the interface between natural aggregate and lightweight aggregate by type, we adopted a method of measuring electrical resistance using an EIS measuring device, which is a non-destructive test, and lightweight bone. The change in the state of the interface was tested on the outside of the material through a blast furnace slag coating. As a result of the experiment, it was confirmed that the electric resistance was about 90% lower than that in the air-dried state through the electrolyte immersion, and the electric resistance differs depending on the type of aggregate and the presence or absence of coating. As a result of the experiment, the difference in compressive strength depending on the type of aggregate and the presence or absence of coating was shown, and the difference in impedance value and phase angle for each type of lightweight aggregate was shown.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.26 no.1
• /
• pp.67-72
• /
• 2022

Concrete prevents corrosion of reinforcing bars due to its strong alkalinity. However, in the sea, strong alkali components with a pH of 12 to 13 are eluted, which adversely affects the ecological environment and growth of marine organisms. In this study, the mechanical properties and durability of the low alkali mortar were evaluated for the development of a low alkali mortar for the 3D printed artificial reefs. As a result of evaluation of strength characteristics, the α-35 mixture, which were produced with fly ash, silica fume and α-hemihydrate gypsum, satisfied the strength requirement 27 MPa in terms of compressive strength. As a result of pH measurement, it was found that mixing with alpha-type hemihydrate gypsum resulted in minimizing pH due to the the formation of calcium sulfate instead of calcium hydroxide production. As a result of the chloride ion penetration resistance test, the α-35 mixture exhibited the best performance, 3844C. As a result of measuring the length change over time, the α-35 mixture showed the shrinkage 33.5% less compared to the Plain mix.

• Journal of the Korea Institute of Construction Safety
• /
• v.6 no.1
• /
• pp.12-18
• /
• 2024

High-rise, large-scale, and diversification of buildings are possible, and the reduction of concrete cross-sections reduces the weight of the structure, thereby increasing or decreasing the height of the floor, securing a large number of floors at the same height, securing a large effective space, and reducing the amount of materials, rebar, and concrete used for designating the foundation floor. In terms of site construction and quality, a low water binder ratio can reduce the occurrence of dry shrinkage and minimize bleeding on the concrete surface. It has the advantage of securing self-fulfilling properties by improving fluidity by using high-performance sensitizers, making it easier to construct the site, and shortening the mold removal period by expressing early strength of concrete. In particular, with the rapid development of concrete-related construction technology in recent years, the application of ultra-high-strength concrete with a design standard strength of 100 MPa or higher is expanding in high-rise buildings. However, although high-rise buildings with more than 120 stories have recently been ordered or scheduled in Korea, the research results of developing ultra-high-strength concrete with more than 130 MPa class considering field applicability and testing and evaluating the actual applicability in the field are insufficient. In this study, in order to confirm the applicability of ultra-high-strength concrete in the field, a preliminary experiment for the member of a reduced simulation was conducted to find the optimal mixing ratio studied through various indoor basic experiments. After that, 130 MPa-class ultra-high-strength concrete was produced in a ready-mixed concrete factory in a mock member similar to the life size, and the flow characteristics, strength characteristics, and hydration heat of concrete were experimentally studied through on-site pump pressing.

• Journal of the Society of Disaster Information
• /
• v.20 no.1
• /
• pp.20-31
• /
• 2024

Purpose: Research and development of high-strength concrete enables high-rise buildings and reduces the self-weight of the structure by reducing the cross-section, thereby reducing the thickness of beams and slabs to build more floors. A large effective space can be secured and the amount of reinforcement and concrete used to designate the base surface can be reduced. Method: In terms of field construction and quality, the effect of reducing the occurrence of drying shrinkage can be confirmed by studying the combination of low water bonding ratio and minimizing bleeding on the concrete surface. Result: The ease of site construction was confirmed due to the high self-charging property due to the increased fluidity by using high-performance water reducing agents, and the advantage of shortening the time to remove the formwork by expressing the early strength of concrete was confirmed. These experimental results show that the field application of ultra-high-strength concrete with a design standard strength of 100 MPa or higher can be expanded in high-rise buildings. Through this study, we experimented and evaluated whether ultra-high-strength concrete with a strength of 130 MPa or higher, considering the applicability of high-rise buildings with more than 120 floors in Korea, could be applied in the field. Conclusion: This study found the optimal mixing ratio studied by various methods of indoor basic experiments to confirm the applicability of ultra-high strength, produced 130MPa ultra-high strength concrete at a ready-mixed concrete factory similar to the real size, and tested the applicability of concrete to the fluidity and strength expression and hydration heat.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.37 no.12
• /
• pp.1599-1608
• /
• 2008

This study aimed to assess the health status based on the anthropometric and biochemical measurements of middle-aged and elderly people living in Andong area. The subjects were 1,384 people (532 males, 852 females) aged 50 years and over (average 62.7 years). The mean anthropometric values for males and females were heights of 163.7 and 151.5 cm; weights 63.6 and 57.3 kg; body mass index (BMI) 23.6 and $24.9kg/m^2$; body fat 21.8 and 31.8%, respectively. Height and weight were lower, however, waist circumference (in female) and BMI were higher than those of the 2001 National Health and Nutrition Survey (NHNS). Obesity incidences of male and female subjects were 28.7% and 47.3% by BMI; 25.8% and 50.8% by % body fat; and 15.6% and 80.9% by waist circumference, respectively. Also, abdominal adiposity was very severe in female subjects of 50s. The mean biochemical measurements of male and female were as follows: systolic and diastolic blood pressure 136.9, 83.8 mmHg and 133.6, 82.5 mmHg; hemoglobin (Hb) 14.3 and 13.0 g/dL; hematocrit (Ht) 44.7 and 39.8%; blood albumin 4.15 and 4.04 g/dL; total-cholesterol 170.0 and 183.1 mg/dL; HDL-cholesterol 43.6 and 42.7 mg/dL; fasting blood glucose 96.7 and 93.0 mg/dL, respectively. Also, the prevalence of biochemically abnormal subjects according to each cut-off point of biochemical measurements were analyzed. The results for male and female were; hypertension 58.0% and 47.2%; iron deficient anemia 19.3% and 20.6% by Hb, 7.2% and 11.9% by Ht; hypoalbuminemia 9.8% and 11.7%; diabetes 12.0% and 10.2%; hypercholesterolemia 19.5% and 30.5%, respectively. From those results we found that hypoalbuminemia, hypertension and hypercholesterolemia were prevalent, and obesity in females of 50s, iron-deficient anemia and diabetes in males of 70 years and over were significant health problems in this area. Therefore, it seems to be necessary to examine their health status periodically and provide the appropriate health and nutrition education program, which includes low sodium intake, balanced diet, exercise and weight control, to prevent the occurrence of chronic diseases.