• Journal of the Korean Society of Safety
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• v.18 no.3
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• pp.109-113
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• 2003

Concrete and shotcrete should withstand the conditions for which they have been designed, without deterioration, over a period of years. But connote and shotcrete are being deteriorated according to aging by internal and external causes. Recently, many studies on the durability of concrete have been conducted But the durability of shotcrete is rarely studied. So, in this study, chloride ion penetration test freeze and thaw test neutralization test were conducted to examine the durability characteristics of shotcrete with several accelerator and chemical admixture types. These results indicate that shotcrete with allah free accelerator and with superplasticizer are durable. Therefore, the present study provides a fm base to make high performance shotcrete.

• Journal of the Korea Institute of Building Construction
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• v.7 no.4
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• pp.117-124
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• 2007

Focused on the material-related aspect for enhancing the durability of concrete, the present study analyzed the effect of glycol ether admixture, which is a chemical admixture that can compact the structure of concrete by entraining air inside the concrete, on the basic physical properties and durability characteristic of the concrete. In analyzing the results of experiment, we examined the basic physical properties and durability characteristic of concrete according to addition rate based on OPC and selected the optimal addition rate. In addition, with the optimal addition rate, we added glycol ether admixture to concrete, which contained fly ash used as binder and high-performance water reducing agent for reducing the unit quantity, and examined changes in the characteristics of the concrete. According to the result, the optimal addition rate of glycol ether admixture was 3% of the unit quantity of cement, and the addition of binder and chemical admixture did not have a significant effect on unhardened concrete but reduced the air content. In addition, concrete showed resistance performance of around 30% to carbonation and around 40% to drying shrinkage. In addition, as for resistance to freezing and thawing, the relative dynamic modulus of elasticity was over around 85% through atmospheric curing. These performances prove the effect.

• Journal of the Korean Ceramic Society
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• v.47 no.5
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• pp.373-380
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• 2010

In this study, we studied on the durability of restorative cement mortar for deteriorated concrete at complex deteriorated conditions as variation of temperature and of humidities. We made a comparison between restorative materials with insulation function and restorative materials without insulation function in items of compressive and bending strength and permeability of water, durability for carbonation, salt damage, diffusion coefficient of salt at complex deterioration conditions like change of temperature, change of humidity, For insulation, we used close-pore type Alumino-Silicate lightweight aggregate and substituted 12 wt% and 15 wt% out of original restorative cement mortar without insulation function. As a result, it was found that original restorative cement mortar without insulation function fail to meet Korean Standard on polymer modified cement mortar for maintenance in concrete structure, but restorative cement mortar with insulation function is in contentment Korean Standard to meet excellent than restorative materials without insulation function for durability at complex deteriorated conditions.

• Korean Chemical Engineering Research
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• v.62 no.1
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• pp.1-6
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• 2024

As the demand for hydrogen electric vehicles for commercial vehicles increases, the durability of PEMFCs must increase more than five times that of passenger cars, so research and development to improve durability is urgent. When the PEMFC membrane electrode assembly (MEA) undergoes chemical degradation, the MEA thickness decreases and pinholes occur. In this study, changes in the performance and durability of the MEA were measured while increasing the clamping pressure of the unit cell after open circuit voltage (OCV) holding, an accelerated chemical degradation experiment. As the clamping pressure increased, the resistance of the polymer membrane and the membrane/electrode contact resistance decreased, improving the I-V performance and reducing the hydrogen permeability. As the hydrogen permeability decreased, the OCV increased. When the pinhole area was removed and the MEA clamping pressure was increased, the hydrogen permeability decreased sharply, confirming that the local degradation has a large effect on the performance and durability of the entire cell. When the pinhole was removed and re-clamping and OCV holding was evaluated, it was confirmed that the durability improved according to the decrease in membrane resistance and hydrogen permeability.

• Korean Chemical Engineering Research
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• v.59 no.4
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• pp.508-513
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• 2021

In order to improve the durability of a proton exchange membrane fuel cells (PEMFC), it is essential to improve the durability of the polymer membrane. In order to improve the durability of the membrane, an e-PTFE support and a radical scavenger are added. In this study, the chemical durability of the reinforced membrane with ePTFE support and the non-reinforced membrane was compared by Fenton reaction. In the Fenton experiment of the polymer membrane without the addition of a radical scavenger, the absorption rate of hydrogen peroxide solution and iron ions through the cross section of the specimen cut into small pieces was higher in the reinforced membrane, so that the fluorine outflow concentration was higher. According to the type and amount of radical scavenger added, the fluorine outflow concentration of the reinforced membrane has a large difference of more than 3 times, indicating that the effect of the radical scavenger was stronger than that of the support.

• Journal of the Korean Ceramic Society
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• v.25 no.2
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• pp.173-183
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• 1988

Effects of oxide additives such as MoO3, MnO2 ZrO2 and Fe2O3 on the phase separation and the chemical durability of sodium borosilicate glasses which are the host of waste glasses have been investigated as the basic study on the nuclear-waste immobilization through vitrification. MoO3 and MnO2 were found to be phase separation promotors which increased the temperature as well as catalyzed nucleation and growth for the phase separation of the 10Na2-O-3OB2O3-6OSiO2 (wt%) parent glass within the immiscibility region. The glasses had the interconnected phase-separated structure as the amount of addition increased. On the other hand, ZrO2 and Fe2O3 were inhibitors which showed the reverse effects to the above promotors. It was also found that addition of MoO3 could cause the phase separaton of the 20Na2O-10B2O3-70SiO2(wt%) glass even within the miscibility region. Addition of ZrO2 and Fe2O3 increased the chemical durability of the parent glass within the immiscibility region. Within the miscibility region, however, the addition of 1.96 wt % of MoO3 increased the chemical durability considerably, while MnO2 had little effects.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.271-274
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• 2001

Recently, we are facing with the trend of demanding high durability concrete for creek structures. When creek structures are deteriorated, it is very difficult to repair them. The objective of this paper is to develop a mixing model for high durability creek concrete having 300kg/$\textrm{cm}^2$ compressive strength. According to the result of durability experiment, high durability concrete for creek structures has high resistance of air permeability, absorption, chloride diffusion, and chemical attack.

• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.3
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• pp.41-49
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• 2003

In this study, durability performance of blended cement mortars is evaluated when various mineral admixtures are used with the cement. A comprehensive evaluation of the effects of mineral admixtures on the mortar performance was made. The properties of fresh and hardened blended mortars investigated include slump flow and compressive strength. The durability characteristics of cement materials incorporating the mineral admixtures under various physical and chemical causes of deterioration was investigated. The laboratory test results indicate that mechanical and durability properties of blended cement mortars have superior performance rather than ordinary cement mortars.

• Journal of the Korean Ceramic Society
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• v.52 no.2
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• pp.140-145
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• 2015

In this study, we verified the relationship among the electrical conductivity, chemical durability, and structure of conductive vanadate glass in which $BO_3$ and $BO_4$ and $V^{4+}$ and $V^{5+}$ coexist simultaneously. We prepared samples of vanadium borophosphate glass with various compositions, given by $50V_2O_5-xB_2O_3-(50-x)P_2O_5$(x = 0 ~ 20 mol%) and $70V_2O_5-xB_2O_3-(70-x)P_2O_5$(x = 0 ~ 10 mol%), and analyzed the electrical conductivity, chemical durability, FT-IR spectroscopy, thermal properties, density, and molar volume. Substituting $B_2O_3$ for $P_2O_5$ was found to improve the electrical conductivity, chemical durability, and thermal properties. From these results, we can draw the following conclusions. First, the electrons shift from the electron rich $V^{4+}$ to the electron deficient $BO_3$ as the $B_2O_3$ content increases. Second, the improvement in chemical durability and thermal properties is attributed to an increase in cross-linked structures by changing from a $BO_3$ structure to a $BO_4$ structure.

• Korean Chemical Engineering Research
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• v.59 no.1
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• pp.11-15
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• 2021

In this study, we tried to develop a method of accelerated degradation of the electrode by simply using a electronic loader without using a potentiostat to evaluate the durability of the electrode catalyst. To this end, the durability of the electrode was evaluated by repeating the stepwise voltage change using the self-generated voltage by introducing oxygen without introducing nitrogen into the cathode. For accurate electrode durability evaluation, that is, in order not to deteriorate the polymer membrane, the high voltage was lowered to 0.9 V in stepwise voltage change and the relative humidity was 100% to suppress degradation of the polymer membrane due to radicals. After 30,000 cycles (50 hours) of voltage change, the electrode active area decreased by 41.4%. It was confirmed that the electrode was deteriorated, but the polymer membrane was not deteriorated, that there was no increase in hydrogen permeability, no decrease in membrane thickness, and no increase in HFR(High Frequency Resistance).