• Journal of the Korean Recycled Construction Resources Institute
• /
• v.8 no.2
• /
• pp.190-197
• /
• 2020

This paper evaluates the mechanical properties and durability of cement matrix blended with mineral admixtures and ferronickel slag(FNS) powder which is an industrial b y-product during ferronickel smelting process. The hydration heat, pore structure, compressive strength, length change, rapid chloride penetration test(RCPT), and freezing and thawing resistance of ternary blended cement matrix were investigated and compared with ordinary portland cement matrix. The result showed that the compressive strength of ternary blended cement matrix using ferronickel slag powder and mineral mixture was low in strength compared to the reference concrete, but recovered to a certain extent by using alkali activator. Length change of cement mortar using FNS powder have shown less shrinkage occurs than the reference specimen. In addition, irrespective of using the alkali-activators, all ternary mix are indicative of the 'very low' range for chloride ion penetrability according to the ASTM C 1202, and the freeze-thaw resistance also showed excellent results.

• 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.

• Resources Recycling
• /
• v.4 no.1
• /
• pp.12-19
• /
• 1995

This study was carried out to remove the iron and impurities usmg hydrocyclone and HGMS for recycling of sludge from the granite stone cutting and polishing industrγ in the basic of chemi떠1 analysis and minerallogical investigation. This sludge consist of 70.9% $SiO_2$ 13.6% $Al_2O_3$ and It also contained 2.52% of $Fe_2O_7$ and 0.29% of $TiO_2$, as a main impurities to decrease the whiteness. As the result of hydrocyclone experiment, It was very good condition that are 100~150 g/l of sludge amount, 2.0~ 2.5 mm of underflow nozzle size, and 1.2~1.6 kg/$\textrm{cm}^2$ of pressure for 85% sludge product with the $-37{\mu}\textrm{m}$ size. $Fe_2O_3$ and $TiO_2$, contents by treatment of HGMS were decreased with 0.65% and 0.07% each at 10,000 gauss of magnetic field strength, and addih$\upsilon$n of Sodium tripolyphosphate as a dispersant was effected to get low grade F Fe,Ol and TiO, concentrate. PhYSIcal properties of this stone sludge product were showed 58.5% of whiteness, 1 13.4% of firing shrinkage and 3.0812 $\textrm{m}^2$/g of specific surface area.

• Journal of Adhesion and Interface
• /
• v.13 no.4
• /
• pp.171-181
• /
• 2012

The demand characteristics of the conventional 12 kinds of epoxy resins which have been used for restoration of the ceramic relics were investigated to provide standards of the effective materials in this study. The result of durability analysis showed that a liquid type is more effective in ceramic relics (low damage, high strength), and a paste type is more effective in earthenware relics (high damage, low strength). The result of workability analysis appears that the liquid type is higher than the paste type, and a slow curing type is higher than a fast curing type in surface hardness. Therefore, in the case of the liquid type which is hard to reprocess due to high surface hardness, it is necessary to conduct a study on improving physical properties by adding filler. The result of the gloss analysis on epoxy resins showed that the liquid type (colorless) has higher gloss than the paste type, and the slow curing type has higher gloss than the fast curing type in liquid types. CDK-520A/520B and Araldite SV 427-2/HV 427-1 showed the most similar gloss to $700^{\circ}C$ earthenware, Devcon 5 minute, EPO-TEK 301-2, and Quik Wood showed the most similar gloss to celadon and whiteware, Quik Wood, EPO-TEK 301-2, and Devcon 5 minute showed the most similar gloss to buncheongware. It is necessary for conservator to decide the range of the restoration surface by predicting the increase and decrease of the restoration surface because most of the epoxy resins caused the volume change in curing process.

• Journal of the Korea Institute of Building Construction
• /
• v.19 no.4
• /
• pp.289-297
• /
• 2019

Epoxy resin adhesives are currently used as adhesives in buildings. Epoxy resin adhesives, which are organic materials, generate harmful substances when producing adhesives, and toxic substances are high in the residential space after installation. In addition, a large amount of carbon monoxide generated from organic materials in the case of a building fire leads to personal injury. This study evaluates the feasibility of inorganic adhesives using pure inorganic materials such as magnesia, phosphate, and borax as inorganic adhesives to replace existing organic adhesives. As a result of the experiment on the selection of adequate phosphate and the characteristics of the addition rate of borax used as a retarder, the potassium phosphate monobasic was obtained as a suitable phosphate and the characteristics according to the borax addition rate were compared with the quality standard of KS F 4923 The hardening shrinkage and heat change rate satisfied the quality standards. The tensile strength was satisfactory when the borax addition rate was 4% or more, but the adhesive strength did not meet the quality standards. Further studies are needed to improve adhesion strength.

• 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 Korean GEO-environmental Society
• /
• v.23 no.9
• /
• pp.17-23
• /
• 2022

Using cement as a road subbase is economical, easily modified and supplemented and has excellent road pavement quality control. In addition, cement adheres well to sandy soils without adhesion, and it plays a role of permanently preserving adhesion in viscous soils with adhesion, so it can be widely applied as stable treatment with the advantages of increased strength, reduced compressibility. and improved durability. However, while cement is excellent in terms of strength for a road subbase, the material properties mean that it is difficult to maintain and reinforce when cracks or fractures occur due to dry shrinkage, and the pH increases in the ground due to hexavalent chromium eluting from cement. which can cause environmental problems such as groundwater contamination. Therefore, this study evaluates the usability of alternatives in the road base layer such as environmentally cementitious stabilizer and on-site soil generated from the site. We intend to reduce the environmental damage and evaluate the durability. To evaluate the applicability of the site, Environmental stability test and freeze-thaw test and wetting-drying test was conducted to evaluate the strength characteristics of alternative materials on the road through the limited performance evaluation of environmentally cementitious stabilizer. The test ranges were set at mixing ratios of 10%, 20%, and 30% and ages of three days, and 28 days old to evaluate the early strength and reference strength according to the mixing ratio of the environmentally cementitious stabilizer.

• 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 Korean Wood Science and Technology
• /
• v.52 no.3
• /
• pp.221-233
• /
• 2024

Lignin, a prominent constituent of woody biomass, is abundant in nature, cost-effective, and contains various functional groups, including hydroxyl groups. Owing to these characteristics, they have the potential to replace petroleum-based polyols in the polyurethane industry, offering a solution to environmental problems linked to resource depletion and CO₂ emissions. However, the structural complexity and low reactivity of lignin present challenges for its direct application in polyurethane materials. In this study, Kraft lignin (KL), a representative technical lignin, was fractionated with ethanol, an eco-friendly solvent, and mixed with conventional polyols in varying proportions to produce polyurethane films. The results of ethanol fractionation showed that the polydispersity of ethanol-soluble lignin (ESL) decreased from 3.71 to 2.72 and the hydroxyl content of ESL increased from 4.20 mmol/g to 5.49 mmol/g. Consequently, the polyurethane prepared by adding ESL was superior to the KL-based film, exhibiting improved miscibility with petrochemical-based polyols and reactivity with isocyanate groups. Consequently, the films using ESL as the polyol exhibited reduced shrinkage and a more uniform structure. Optical microscope and scanning electron microscope observations confirmed that lignin aggregation was lower in polyurethane with ESL than in that with KL. When the hydrophobicity of the samples was measured using the water contact angle, the addition of ESL resulted in higher hydrophobicity. In addition, as the amount of ESL added increased, an increase of 7.4% in the residual char was observed, and a 4.04% increase in Tmax the thermal stability of the produced polyurethane was effectively improved.

• Journal of Wetlands Research
• /
• v.26 no.2
• /
• pp.139-146
• /
• 2024

Various injection materials, such as asphalt-based injection materials, urethane-based injection materials, cement- based injection materials, and acrylic-based injection materials, are used for the repair of aged conduits and underground structures with cracks. In this study, research was conducted on an environmentally friendly acrylic- based leak repair material that exhibits good curing properties even in humid conditions and stability in temperature fluctuations. To compare the performance of the improved acrylic leak repair material with the existing acrylate injection material, experiments were conducted using KS standard methods, including underwater length change rate tests, underwater leakage resistance tests, and chemical performance tests. The comparative experiments revealed that the improved acrylic leak repair material showed no changes in shrinkage due to humidity, temperature variations, or chemical reactions compared to the existing acrylate injection material. In the underwater resistance test, the improved acrylic leak repair material did not show any leakage. Additionally, to assess the environmental impact of the improved acrylic leak repair material, acute fish toxicity tests and acute oral toxicity tests were conducted, and the results showed no mortality and no specific concerns with the test specimens. The experimental results led to the conclusion that the improved acrylic leak repair material is considered to be superior in performance, environmentally safe, and harmless to the human body. Based on various experimental results, it is inferred that the improved acrylic leak repair material is suitable for use as a repair material for cracks in manholes and underground structures compared to the existing acrylate repair material. This study aims to propose valuable data for future technological development by evaluating the applicability of acrylic leak repair materials.