• Resources Recycling
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• v.24 no.5
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• pp.63-71
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• 2015

The purpose of this study is to investigate the optimum replacement rate and material properties of eco-friendly recycled concrete using recycled coarse aggregates and rapid-chilled steel slag fine aggregates. The replacement rate of recycled coarse aggregates was increased from 30% to 50% of total volume of coarse aggregates and the rapid-chilled steel slag aggregates were substituted for 10% to 50% of total volume of fine aggregates. As a result, the increment of recycled coarse aggregates in concrete caused the reduction of the compressive strength. On the other hand, as increasing the replacement ratio of rapid chilled steel slag aggregates, the compressive strength was enhanced. Furthermore, the optimum use of rapid chilled steel slag aggregates was suggested up to 20~30% of fine aggregates and the use of it could be helpful to expand the replacement rate of recycled aggregates.

• Journal of Korea Water Resources Association
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• v.43 no.9
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• pp.835-842
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• 2010

This paper attempts to examine households' willingness to pay (WTP) for ground water pollution improvement which can be used in cost-benefit analysis on the project for developing the soil pollution control technique. We applied a contingent valuation (CV) method to obtain at least a preliminary evaluation of the WTP. The CV survey was rigorously designed to comply with the guidelines for best-practiced CV studies. We surveyed a randomly selected sample of 500 households in Seoul metropolitan area and asked respondents questions in person-to-person interviews about how they would be willing to pay for the program. Respondents overall accepted the contingent market and were willing to contribute a significant amount (1,195 to 1,552 won), on average, per household per year. The aggregate value of the project for developing the soil pollution control technique amounts to approximately 20.3 billion won per year. The household values can be the benefits that ensue from the project and compared with the costs of the program to determine whether the project is economically desirable.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.3
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• pp.55-62
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• 2010

This is an experimental research in order to judge the applicability of sewage sludge incineration ash having applied the mixing proportion needed to manufacture bricks and to do plaster work with addition of hwangtoh and slaked lime as a part of the methods for utilizing the wastes produced from sewage sludge incineration ash. Based on the results from experiment and analysis, it is judged that, in case of mixing proportion of 1:2 for the purpose of plastering and masonry work, the cement mortar produced by using a 10% addition ratio of sewage sludge incineration ash with mixture of hwangtoh covering all range of addition ratio, and also the cement mortar produced by using a 20% of sewage sludge incineration ash together with 0% and 10% addition ratio of hwangtoh, was possible to be applied to the practical use. In case of mixing proportion of 1:7 for manufacture of bricks and blocks, if such brick and block products are produced with 10% and 20% addition ratio of sewage sludge incineration ash having added aggregate fines or stone dust that has been actually used in brick and block manufacturing, it is judged that these bricks and blocks could be practically used in the job sites, although strength development is a little bit lower.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.1445-1449
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• 2004

Even though there can be a relative long-term or short-term change of their size in natural beaches due to various changes of sea condition such as the location, weather condition (wind and rain) and sea water flow, the budget of deposits in a specific area is generally regarded to be in a condition of equilibrium in terms of technology. However, as coasts are developed by many different kinds of ways (such as construction of sea walls and estuarine, dredging for gathering the aggregate and shore protection construction for establishing a structure) and sources of silt and gravel from rivers are decreased in balanced beaches, the beaches are in a serious danger of lack of sand and sand sources which are one of the maul elements to consist of them. Many swimming beaches in East Sea are directly exposed by waves generated and transmitted from outer seas. On the other hand, the Song-Do sandy beach which is this study's target area has a great condition for beach development because it locates the deepest place that is relatively shallow in Young-Il Man and there is big energy decrease given to waves from outer seas while the waves are reaching the Song-Do beach. Nevertheless, it is considered that artificial condition changes such as dredging for site extension by POSCO, getting straight of Hyoung-San Gang river flow and extension of Po-Hang harbor caused the sand loss of the beach. Therefore, some recovery plans of Song-Do sandy beach will be presented in this study and they will be compared and examined each other by numerical modeling experiment. After that, the best plan will be recommended.

• Journal of Korea Water Resources Association
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• v.30 no.4
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• pp.367-377
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• 1997

In order to set public policy to overcome 'water crises' on both quantity and quality of water, we looked into the national-economic role of Korea water utility by two approaches. First, we examined the relationship between water consumption and economic growth during 1978-94, a period of rapid increase in water consumption caused by prompt industrialization and urbanization. The price and income elasticities of aggregate and sectoral demand for water were estimated. Second, we developed a static input-output(I-O) framework for analysing water issues in the short run. In addition, we discussed two topics in its application: i) sectoral failure(shortage) costs by supply-driven I-O model, ii) Leontief price model's sectoral pervasive effects of price due to rise in water rate. In conclusion, we found that investments to water sector and water shortage has a big influence on the standard of living and industrial production. Also we found that raising water rate to encourage conservation or to create investment funds decreases demand for water significantly but has a small influence on overall price levels.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.3
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• pp.244-251
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• 2015

The paper evaluates the effect of the physical property, fineness modulus (FM) and replacement ratio of crushed sand on the characteristics of concrete. This is intended to use crushed sand from Daegu-Kyungbuk region as the fine aggregate of concrete. The experimental result indicates that the replacement ratio of crushed sand needs to be less than 50% to satisfy the mixed gradation of both natural and crushed sand when their FMs are 2.0 and 3.2, respectively. The slump of concrete with crushed sand increased as the replacement ratio of crushed sand increased, while the workability of concrete with the replacement ratio of more than 75% was significantly reduced. The air content and bleeding rate of concrete was reduced as the replacement ratio increased. Furthermore, due to the enhancement of the concrete adhesive regardless of the FM of crushed sand, compressive strength of concrete tended to improve as the replacement ratio increased.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.4
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• pp.342-347
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• 2015

This study is basic experiment which prevents indiscriminate reclamation and recycles the wasted tire in order to solve environmental pollution according to generation rate of the wasted tire from recently industrial development. By applying as the substitute material of the lightweight aggregate among the constructional materials in order to evaluate the lightness of the wasted tire chip and suggest the recycling plan of the wasted tire chip. The prior experiment did the replacement ratio of the wasted tire with 20%, 40%, 60%, 80%, 100%, etc. and made a study on the strength and density properties. Based on the prior experiment of wasted tire, the replacement ratio was fixed at 15, 20, 25%, particle size of wasted tire was fixed at 0.2, 0.8, 1~2, 3~5, 5~7(mm). As a result, it is supposed that the best replacement ratio and particle size are 15% and 1~2mm, respectively.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.2
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• pp.165-171
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• 2016

The objective of this study is to evaluate the compressive strength development and ecological characteristics of mortars using expanded vermiculite absorbing bacteria as a fundamental investigation to develop precast eco-concrete products. For bacterial growth under the high-alkalinity and high-dried environments within hardened mortars and for creating plant growth function to mortars, Bacillus alcalophilus and Rhodoblastus acidophilus were separated and cultured. The cultured bacteria were absorbed into expanded vermiculite selected for bacteria shelter. The expanded vermiculite absorbing bacteria was then added into mortar mixture as a volumetric replacement of fine aggregate. Test results showed that the developed technology is very effective in enhancing the plant growth onto the hardened mortars and reducing the COD and T-N concentration in raw water. The optimum replacement level of expanded vermiculite absorbing bacteria can be recommended to be less than 10% considering the compressive strength development and cost of mortars along with the ecological effectiveness.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.3
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• pp.263-268
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• 2020

The purpose of this study is to investigate the damping properties of polyurethane composites incorporating waste tire rubber powder and preplaced coarse aggregates. Four types of polyurethane-based composites were manufactured, and longitudinal impact tests were performed. And vibration signals in the time domain and frequency domain were measured and values of damping ratio for each specimen were calculated. Test results showed that the damping ratios of polyurethane composites, in which the amount of polyurethane was reduced by 10.6% and 21.2% through incorporation of rubber particles, were 8.4% and 4.6% lower than that of pure polyurethane. The damping ratio of the polyurethane composite produced in a similar manner to the prepact concrete production method was found to be 22% lower than that of pure polyurethane, however, the amount of polyurethane was reduced by 50% and the stiffness was 25.7 times higher than that of pure polyurethane.

• Resources Recycling
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• v.8 no.4
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• pp.3-10
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• 1999

An experimental study for manufacturing lightweight aggregates from sewage sludge ash of sewage treatment facilities was carned out in senses of sludge disposal and utilization. In case of SA alone, aggregates with S.G. 1.67 was obtained at sintering temperature of $1250^{\circ}C$, and heating rate affects little to volume expansion rate and volume expansion rate was decreased more or less by heating time. In case of adding 10 wt% of RFCC to SA, lightweight aggregates with S.G. 1.07 was obtained and volume expansion rate was increased by heating time. The optimum adding amounts of RFCC to manufacture lightweight aggregates was 10wt% and the condition that shows maximum volume expansion rate was $20^{\circ}C/min$ of heating rate, $1250^{\circ}C$ of sintering temperature and 50 mmutes of heating time. According to adding amounts of RFCC, Compressive strength of sample results in 30 wt% RFCC>SA>20 wt% RFCC>10 wt% RFCC.