• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.1
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• pp.115-123
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• 1990

The purpose of this study was to examine the uses of coal ash as a type of construction material. The methods of examination were chemical anlysis, soil laboratory test and the soil vibration test. Materials used were coal ash obtained as a by-product from 5 thermal power plants in Yongdong, Yongwol, Sochon(anthracite coal) and in Samchonpo and Honam (bituminous coal). Over 70% of the coal ash consisted of silica and alumina. The fly ash grain size showed a uniform distribution from fine-sand to silt, and that of the bottom ash showed from sand to gravel. The specific gravity and density of the coal ash were low. The long term strength increased gradually due to the self-setting property resulting from pozzolanic activity. The shear strength was higher than that of general soil. Cohesion and optimum moisture content of anthracite coal ash were higher than bituminous coal ash, whereas the maximum dry density was higher in bituminous coal ash. The coal ash dynamic Young's modulous curve range was similar to that of general soil. Of the results from the soil vibration test by car-running, the size relative acceleration level in the ash pond was higher than that of natural ground, but the damping ratio was lower than that of natural ground near the ash pond. The coal ash has more advantageous engineering properties than general soil with particles of the same size. For example, the California Bearing Ratio of the bottom ash at both Yongdong and Yongwol was 77~137%. Therefore we expect that if further study is done, coal ash can be used as a construction material when reclaiming seashore, construction embankments, road construction, making right-weight aggregate, or as a general construction material.

• KDI Journal of Economic Policy
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• v.32 no.4
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• pp.1-34
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• 2010

We conduct a comprehensive risk analysis of household debt in Korea for the first time using the whole sample credit bureau (CB) data of 2.2 million individual debtors. After analysing debt service capacity profiles of debtor groups classified by the borrower characteristics such as income, age, occupation, credit scoring, and the type of creditor business companies, we investigate the impact of interest rate and income changes on debt service-to-income ratios (DTIs) and default rates of respective debtor groups. Empirical results indicate that debt service burdens are relatively high for low income wage earners, high income self-employed, low income capital and card loan holders, and high income mutual savings loan holders. We also find that debtors from multiple financial companies are particularly weak in their debt service capacity. The scenario analysis indicates that financial companies, with the current level of capital buffers, may be able to absorb negative consequences arising from the increase in DTIs and loan default rates if the interest rate and income changes remain modest. However, the negative consequences may fall disproportionately on non-bank financial companies such as capital, credit card, and mutual savings banks, whose debtors' DTIs are already high. We also find that the refinancing risk of household debt is relatively high in Korea as more than half of household mortgage debts are bullet loans. As the DTIs of mortgage loan holders are already high, under the current DTI regulation, mortgage loans may not be readily refinanced especially when the interest rate rises. Disruptions in mortgage loan refinancing may put downward pressure on housing prices, which may in turn magnify refinancing risk under the current loan-to-value (LTV) regulation. Overall our analysis suggests that, for more effective monitoring of household debt risk, it is necessary to combine existing surveillance schemes based on macro aggregate indicators with more comprehensive and detailed risk analyses based on micro individual data.