• Journal of the Korea Institute of Building Construction
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• v.17 no.1
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• pp.47-54
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• 2017

Cement industry is typical carbon-emission industry. If the industrial by-products(granulated blast-furnace slag (GGBFS), fly ash, etc.) are used a large amount, it might be able to reduce cement consumption and mitigate carbon emissions. In this case, however, decrease of early strength is relatively large. Therefore, there is a limitation in increase of the amount of substitute. Considering these circumstances, it would be a good solution to reduce carbon emissions in cement industry to improve the performances of mixed cement through proper alkali-activation in Portland blended cement using GGBFS or fly ash. Therefore, this study prepared concrete in ready-mixed concrete manufacturing facilities with an addition of a binder which used 2.0% modified alkali sulfate activator after mixing Portland cement, GGBFS and fly ash in the ratio of 4:4:2 and assessed its basic properties. The results found the followings: The use of modified alkali-sulfate activator slightly reduced slump and shortened setting time. As a result, bleeding capacity decreased while early strength improved. In addition, there is no big difference in carbonation resistance. It appears that there should be continued experiments and analyses on the related long-term aged specimens.

• Journal of the Korea institute for structural maintenance and inspection
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• v.17 no.5
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• pp.77-86
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• 2013

This study investigates the fundamental properties of the water-binder (W/B) ratio and fine aggregate-binder (F/B) ratio in the alkali-activated slag cement (AASC) mortar. The W/B ratios are 0.35, 0.40, 0.45, and 0.50, respectively. And then the F/B ratios varied between 1.00 and 3.00 at a constant increment of 0.25. The alkali activator was an 2M and 4M NaOH. The measured mechanical properties were compared, flow, compressive strength, absorption, ultra sonic velocity, and dry shrinkage. The flow, compressive strength, absorption, ultra sonic velocity and dry shrinkage decreased with increases W/B ratio. The compressive strength decreases with increase F/B ratio at same W/B ratio. Also, at certain value of F/B ratio significant increase in strength is observed. And S2 (river sand 2) had lower physical properties than S1 (river sand 1) due to the fineness modulus. The results of experiments indicated that the mechanical properties of AASC depended on the W/B ratio and F/B ratio. The optimum range for W/B ratios and F/B ratios of AASC is suggested that the F/B ratios by 1.75~2.50 at each W/B ratios. Moreover, the W/(B+F) ratios between 0.13 and 0.14 had a beneficial effect on the design of AASC mortar.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.5376-5383
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• 2011

The objective of this study is the development of carbon-recycle technology, that converts carbon dioxide captured from flue gas to carbon monoxide or carbon for reuse in industrial fields. It is difficult to decompose $CO_2$ because $CO_2$ is very stable molecule. And then metal oxide was used as an activation agent or catalyst for the decomposition of $CO_2$ at low temperature. Metal oxides, which converts $CO_2$ to CO or C, were prepared using Ni-ferrite by solid state method and hydrothermal synthesis in this study. TPR/TPO and TGA were used as an analysis method to analyze the decomposition characteristics of $CO_2$. As the results, the reduction area of $H_2$ was high value at 15 wt% of NiO and the decomposition area of $CO_2$ was superior capacity at 5 wt% of NiO. However, TGA data showed contrary results that reduction area of $H_2$ was 28.47wt% and oxidation area by $CO_2$ was 26.95wt% at 2.5 wt% of NiO, one of the Ni-ferrite powders synthesized using solid state method. $CO_2$ decomposition efficiency was 94.66% and it is excellent results in comparison with previous studies.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.11
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• pp.5357-5364
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• 2011

The objective of this study is development of carbon recycle technology which convert carbon dioxide captured from flue gas to carbon monoxide or carbon and reuse in industrial fields. Since carbon dioxide is very stable and difficult to decompose, metal oxide was used as activation agent for the decomposition of carbon dioxide at low temperature. Metal oxides which convert $CO_2$ to CO or carbon were prepared using Ba-ferrite by solid and hydrothermal synthesis. TPR/TPO and TGA were used in this study. The results of TPR by H2 and TPO by $CO_2$ showed that Ba-ferrite powders synthesized by hydrothermal method were better than those by solid method. TGA showed contrary results that reduction of Ba-ferrite powders synthesized using solid method by $H_2$ was 21.96 wt%, oxidation by $CO_2$ was 21.24 wt% and 96.72 wt% of $CO_2$ decomposition efficiency showing excellent oxidation-reduction characteristics at $500^{\circ}C$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.6
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• pp.720-727
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• 2017

This study determined the optimum mix proportions for volcanic-ash-based geopolymer by analyzing the flow, setting time, and compressive strength. $Na2SiO_3$ and NaOH were used as alkali activators, and NaOH concentrations of 2, 4, 6, and 8M were used for different experimental cases. The A/B ratios examined were 0.25, 0.3, 0.35, 0.4, and 0.45, and the ratios of volcanic ash to blast furnace slag binder were 7:3, 6:4, and 5:5. In the experiment, the flow and setting time tended to decrease and the compressive strength increased as the molarity of NaOH in the geopolymer increased. The optimum molarity of NaOH was determined to be 4M. As the A/B ratio increased, the setting time decreased and the compressive strength increased. The most advantageous A/B ratio for the setting time and strength was 0.35. Increasing the ratio of volcanic ash resulted in a longer setting time and lower compressive strength. The optimum binder ratio was chosen as 6:4 based on the setting time and compressive strength. Thus, 4M of NaOH, an A/B ratio of 0.35, and binder ratio of 6:4 are considered as the proper parameters for the volcanic-ash-based geopolymer.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.111-117
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• 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
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• v.25 no.6
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• pp.73-81
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• 2016

Geopolymers produced from aluminosilicate materials such as metakaolin and coal ash react with alkali activators and show higher fire resistance than portland cement, due to amorphous inorganic polymer. The percentage of thermal shrinkage of geopolymers ranges from less than 0.5 % to about 3 % until $600^{\circ}C$, and reaches about 5 ~ 7 % before melting. In this study, geopolymers paste having Si/Al = 1.5 and being mixed with carbon nanofibers, silicon carbide, pyrex glass, and vermiculite, and ISO sand were studied in order to understand the compressive strength and the effects of thermal shrinkage of geopolymers. The compressive strength of geopolymers mixed by carbon nanofibers, silicon carbide, pyrex glass, or vermiculite was similar in the range from 35 to 40 MPa. The average compressive strength of a geopolymers mixed with 30 wt.% of ISO sand was lowest of 28 MPa. Thermal shrinkage of geopolymers mixed with ISO sand decreased to about 25 % of paste. This is because the aggregate particles expanded on firing and to compensate the shrinkage of paste. The densification of the geopolymer matrix and the increase of porosity by sintering at $900^{\circ}C$ were observed regardless of fillers.

• Applied Chemistry for Engineering
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• v.22 no.5
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• pp.555-561
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• 2011

The objective of this study is the development of carbon recycle technology which converts $CO_2$ captured from flue gas to CO or carbon and reuse in industrial fields. Since $CO_2$ is very stable and difficult to decompose, metal oxide was used as an activation agent for the decomposition of $CO_2$ at low temperature. Metal oxides which convert $CO_2$ to CO or carbon at $500^{\circ}C$ were prepared using Zn-ferrite by the solid state reaction and hydrothermal synthesis. The behaviors of $CO_2$ decomposition were studied using temperature programmed reduction/oxidation (TPR/TPO) and thermogravimetric analyzer (TGA). Zn-ferrite containing 5 wt% ZnO showed the largest reduction and oxidation. Reduction by $H_2$ was 26.53 wt%, oxidation by $CO_2$ was 25.73 wt% and 96.98% of adsorbed $CO_2$ was decomposed to $CO_2$ and carbon with excellent oxidation-reduction behaviors.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.1
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• pp.85-92
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• 2021

The purpose of this study is to investigate the properties of hardener-free epoxy-modified mortars(EMMs) using ground granulated blast furnace slag(GGBFS) and alkali activators. The hardener-free EMMs with a GGBFS content of 20% using 4 types of alkali activators were prepared with various polymer-binder ratios, and tested for strengths, water absorption, carbonation depth, chloride ion and H2SO4 penetration depth. The conclusions obtained from the test results are summarized as follows: The compressive strength of the EMMs with a GGBFS content of 20% attains a maximum at a polymer-binder ratio of 10%. The flexural strength of the hardener-free EMMs using Ca(OH)2 as a alkali activator is improved with increasing polymer-binder ratios. However, the flexural strength of the EMMs using NaCO3, Na2SO4 and Li2CO3 is gradually decreased with increasing polymer-binder ratios. Regardless of the type of alkali activator, the water absorption, chloride ion penetration and carbonation depth are remarkably decreased with increasing polymer-binder ratios due to the epoxy film formed in the EMMs. The H2SO4 penetration depth of the hardener-free EMMs with a GGBFS content of 20% is gradually increased with increasing polymer-binder ratio. In this study, the properties of hardener-free EMMs using Ca(OH)2 as a alkali activator are more excellent than those of other alkali activators.

• Journal of Korean society of Dental Hygiene
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• v.23 no.4
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• pp.219-226
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• 2023

Objectives: This study aimed to investigate the effects of rhubarb extract on osteoclast differentiation in bone marrow-derived macrophages (BMMs). Osteoclasts are vital for bone resorption and remodeling. Osteoclast dysregulation can contribute to various bone-related disorders that directly affect oral health. Rhubarb, a medicinal plant with anti-inflammatory properties, has been shown to modulate bone metabolism. Methods: BMMs were isolated from the femurs and tibias of 5-week-old C57BL/6 mice and cultured in the presence of mouse macrophage colony-stimulating factor (M-CSF) for 3 days. Subsequently, BMMs were treated with M-CSF and receptor activator of nuclear factor-κB ligand (RANKL) to induce osteoclast differentiation. Results: Rhubarb extract effectively suppressed osteoclast differentiation in BMMs. Furthermore, rhubarb extract inhibited the mRNA expression of tartrate-resistant acid phosphatase (TRAP) and cathepsin K (CTSK), which are essential for osteoclastogenesis. Moreover, it inhibited the RANKL-induced expression of nuclear factor of activated T cell c1 (NFATc1), a crucial transcription factor in osteoclast differentiation. Conclusions: These results suggest that rhubarb extract promotes oral health by inhibiting osteoclastogenesis in BMMs. Thus, rhubarb extract shows promise as a therapeutic agent for bone-related disorders that directly affect oral health, particularly those associated with abnormal osteoclast activity. Further research and exploration of the underlying mechanisms are warranted to fully understand their potential clinical applications.