• Magazine of RCR
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• v.9 no.1
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• pp.29-33
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• 2014

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.1
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• pp.85-93
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• 2017

This paper presents mechanical properties and carbonation behavior of the recycled aggregate concretes(RAC) in which natural aggregate was replaced by recycled coarse aggregate and fine aggregate by specified concrete strength levels(21, 35, 50MPa). A total of 18 RAC were produced and classified into six series, each of which included three mixes designed with three specified concrete strength levels of 21MPa, 35MPa and 50MPa and three recycled aggregate replacement ratios of 0, 50 and 100%. Physical and mechanical properties of RAC were tested for slump test, compressive strength, and carbonation depth. The test results indicated that the slump of RAC could be improved or same by recycled coarse aggregate replacement ratios, when compared with natural aggregate. But slump of RAC was decreased as the recycled fine aggregate replacement ratios increase. Also, the test results showed that the compressive strength was decreased as the recycled aggregate replacement ratios increased and it had a conspicuous tendency to decrease when the content of the recycled aggregate exceeded 50%. Furthermore, the result indicated that the measured carbonation depth increases by 40% with the increase of the recycled aggregate replacement. In the case of the concrete having low level compressive strength, the increase of carbonation depth tends to be higher when using the RCA. However, the trend of carbonation resistivity in high level compressive strength concrete is similar to that obtained in natural aggregate concrete. Therefore, an advance on the admixture application and mix ratio control are required to improve the carbonation resistivity when using the recycled aggregate in large scale.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.18 no.1_2
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• pp.27-32
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• 2012

There are many possibilities that recycled papers adulterate contaminants during the process. The objective of this research was to evaluate safety of paper-based packaging materials for food, especially commercial pizza boxes in Korea. Ultimately, we compared recycled and non-recycled commercial paper packaging materials. This study was based on Korean Food and Drug Administration (KFDA) regulation. PCBs were measured by GC-ECD. Arsenic and lead were analyzed using an ICP-MS. Formaldehyde was determined by LC-MS. Fluorescent materials were detected by UV lamp. The result of this study shows that non-recycled paper packaging materials meets all the tested hygienic specifications for food packaging materials, whereas recycled paper-based paperboard box may be contaminated by fluorescent whitening agent. Though these results need to be further studied, it is recommended to avoid using recycled paper in direct contact with food when used in food packaging.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.36 no.4 s.107
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• pp.1-8
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• 2004

Linerboards and corrugating mediums are being produced using recycled old corrugated containers (OCC) as major raw materials. The utilization rate of recycled fibers is ex­pected to increase further in the future to reduce raw material cost. Use of recycled fibers as raw materials for linerboard, however, causes many problems for papermakers. As the utilization rate of recycled fiber and number of recycling of fibers increases, quality and process problems including strength reduction and deterioration of machine runn­ability will increase. To overcome the problem of strength reduction associated with the use of recycled fibrous materials for producing quality linerboards, diverse extensive research efforts and new technological approaches have been taken. In this study, disintegration characteristics of aee was evaluated by determining the unslushed contents. The amount of unslushed content of KOCC was lower than AOCC. But contaminants content of KOCC was higher than AOCC. As the consistency in disintegration increased, the amount of unslushed fiber content decreased.

• International Journal of Concrete Structures and Materials
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• v.9 no.1
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• pp.1-20
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• 2015

This work is devoted to the study of fresh and hardened properties of concrete containing recycled gravel. Four formulations were studied, the concrete of reference and three concretes containing recycled gravel with 30, 65 and 100 % replacement ratios. All materials were formulated on the basis of S4 class of flowability and a target C35 class of compressive strength according to the standard EN 206-1. The paper first presents the mix design method which was based on the optimization of cementitious paste and granular skeleton, then discusses experimental results. The results show that the elastic modulus and the tensile strength decrease while the peak strain in compression increases. Correlation with the water porosity is also established. The validity of analytical expressions proposed by Eurocode 2 is also discussed. The obtained results, together with results from the literature, show that these relationships do not predict adequately the mechanical properties as well as the stress-strain curve of tested materials. New expressions were established to predict the elastic modulus and the peak strain from the compressive strength of natural concrete. It was found that the proposed relationship E-$f_c$ is applicable for any type of concrete while the effect of substitution has to be introduced into the stress-strain (${\varepsilon}_{c1}-f_c$) relationship for recycled aggregate concrete. For the full stress-strain curve, the model of Carreira and Chu seems more adequate.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.4
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• pp.314-320
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• 2014

Although the cement industry serves as the cornerstone of the construction industry by supplying one of its fundamental materials, it confronts new environmental challenges due to the problem of the $CO_2$ generated from raw materials and fuel used in the cement manufacturing process. Also, concrete structures can be decomposed and reused as construction materials. Simply in terms of the cyclic processing of $CO_2$, recycling waste concrete to manufacture recycled aggregate or recycling waste concrete powder, which is the material for cement can be considered optimally environment-friendly practices. This study contributes to the aim of manufacturing high value added materials that exploits the chemical properties of the waste concrete powder. From the research results, waste concrete powder is feasible to use to produce low carbon type recycled cement.

• Resources Recycling
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• v.30 no.3
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• pp.55-62
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• 2021

In Korea, a good recycled product (GR) certification system was introduced in 1997 to improve resource and energy use efficiency. However, in industry and society, recycled products are not used well because of the lack of awareness of recycled materials. In this study, the status of domestic and international quality standards for nickel materials was investigated, and the purity and electrochemical properties of nickel sulfate prepared from ore and nickel sulfate recovered from waste lithium-ion batteries were evaluated during the electroplating process. As a result of the test, it was found that there is no quality difference between recycled nickel sulfate and high-purity nickel sulfate reagents when used in the electroplating industry.

• Journal of the Korean GEO-environmental Society
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• v.1 no.1
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• pp.43-50
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• 2000

This paper presents the engineering property of light weight soil made of soil mixed with recycled stylofoam and stabilizer. Recycled stylofoam beads is able to use by lightweight fill materials because it is light, adiabatic, and effective for vibration interception. Especially, recycled stylofoam beads is easy to supply because stylofoam have been recycle item in 1996. In this study, physical and geotechnical properties of the light weight mixed soil(weathered granite soil mixed with Stylofoam Beads) were analyzed by laboratory experiments to examine its suitability for backfill materials. Laboratory tests were performed to evaluated strength, bearing capacity, weight, permeability, microphotograph analysis with variation of mixing ratio. Based on the results, it is concluded that the use of recycled stylofoam beads is acceptable lightweight fill.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.969-978
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• 2010

In this study, a laboratory model test on utilization of recycled aggregates and crushed stone as vertical drains to use alternative material of sand in soft ground is performed. The vertical and horizontal coefficient of permeability of the recycled aggregates and crushed stone showed largely 1.2~4.0 times and 3.0~3.3 times greater than sand, respectively. Therefore, it showed enough to be an alternative material to the sand which had been being used as the vertical and horizontal drainage material before. The variations of pore water pressure with time showed constantly regardless of the load in all vertical drainage materials. When water level drops suddenly, the pore water pressure of the recycled aggregate and crushed aggregate is reduced to nearly zero. Therefore, it was applicable to the field because discharge capacity was similarity to that of sand. The settlement in crushed aggregates and recycled aggregate decreases gradually with the load increase. When water level drops suddenly, earth pressure in all drains materials was evaluated the equivalent drainage capacity similarity to sand because it show approaching the nearly zero.

• International Journal of Concrete Structures and Materials
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• v.6 no.4
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• pp.239-246
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• 2012

Pervious concrete is a tailored-property concrete with high water permeability which allow the passage of water to flow through easily through the existing interconnected large pore structure. This paper reports the results of an experimental investigation into the development of pervious concrete with reduced cement content and recycled concrete aggregate for sustainable permeable pavement construction. High fineness ground granulated blast furnace slag was used to replace up to 70 % cement by weight. The properties of the pervious concrete were evaluated by determining the compressive strength at 7 and 28 days, void content and water permeability under falling head. The compressive strength of pervious concrete increased with a reduction in the maximum aggregate size from 20 to 13 mm. The relationship between 28-day compressive strength and porosity for pervious concrete was adversely affected by the use of recycled concrete aggregate instead of natural aggregate. However, the binder materials type, age, aggregate size and test specimen shape had marginal effect on the strength-porosity relationship. The results also showed that the water permeability of pervious concrete is primarily influenced by the porosity and not affected by the use of recycled concrete aggregate in place of natural aggregate. The empirical inter-relationships developed among porosity, compressive strength and water permeability could be used in the mix design of pervious concrete with either natural or recycled concrete aggregates to meet the specification requirements of compressive strength and water permeability.