• Proceedings of the Korea Concrete Institute Conference
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• 1992.10a
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• pp.44-49
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• 1992

Selected strength characteristics of recycled concrete using crushed waste concrete were compared with those of conventional concrete using natural aggregate. Compressive strength, bonding at the interface between recycled aggregate and fresh mortar, strain and deflection under three-point bending were evaluated. Recycled concrete, in general, showed lower compressive strength, lower edlastic modulus, higher stain and higher deflection under the same loading level, compared with those of conventional concretes. However, the strength retaining ratios of recycled concretes were higher than those of conventional concretes. The compressive strength which is one of the most important load carrying capacities of concrete should be improved for successful re-use of waste concrete in structural concrete.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2001.11a
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• pp.183-199
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• 2001

Alternative way of shaping fibers suitable for papermaking was introduced. Impact refining, which was done simply by hitting wet fibers with a metal weight vertically, was intended to keep the fibers from shortening and to cause mostly internal fibrillation. Virgin chemical pulp, its recycled one and OCC were used in the experiment. It was noticed from the experiment that impact refining on virgin chemical pulp kept the fiber length and Increased bonding properties greatly, However, in the recycled fibers from the chemical pulp, fiber length and bonding properties were decreased. In OCC, which seems to contain fractions of semi-chemical pulp and mechanical pulp (GP), and which is recycled pulp from corrugated boxes, fiber length and bonding properties were decreased disastrously. We believe recycled cellulosic fibers (recycled chemical pulp and OCC in this case), which went through hornification, were less resistant to the mechanical impact than virgin chemical pulp. For virgin chemical pulp, impact refining allowed no significant fiber length shortening, high WRV, and high mechanical strength.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.04a
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• pp.254-259
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• 1994

Recycling of waste concrete will contribute not only to the solution of a growing waste disposal problem, also help to conserve natural resources of aggregate and to secure future supply of reasonably priced aggregates for building construction purpose within large urban areas. But there recycled aggregates are more porous and less resistant to mechanical actions. In comparison with natural aggrete concrete, recycled aggregate concrete shows reductions in strength and other engineering properties. And it may also be less durable due to increase in porosity and permeability. Economical ways of improving the quality of recycled aggregate concrete are: (1)by reducing the water-cement ratio; (2)by reducing the water content using a superplasticizer without affecting the workability; (3)addition of pozzolan, such as fly ash; and (4)blending of recycled aggregate with the natural aggretes.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.81-82
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• 2012

The purpose of this study is the hydration properties of motar using Blast-Furnace Slag(BFS) with water elured from recycled coarse aggregate. The results of the experiment show that the water eluted from recycled coarse aggregate mixed with blast furnace slag has comparatively higher hydration activity than the mortar not mixed with one in early-age mortar causing the calcium hydroxide in the recycled coarse aggregate to work on as a stimulus to the hydration of ground granulated blast furnace slag. BFS mixed with the eluting water the hydration reaction was a promotion.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.31 no.5
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• pp.18-23
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• 1999

This study examined the effects of multiple recycling on deinkability and properties of recycled paper from laser computer printout(LCPO). First, alkaline paper with a 20% printed area was disintegrated by TAPPI standard disintegrator. After dewatering , the pulp was followed by flotation, handsheet making, and drying at room temperature, in order. A sequence of printing , disintegrating, flotating , handsheet making and drying was one recycling cycle and this cyclic treatment was repeateed from zero to five times. The residual ink content in recycled handsheets by SEM-EDXA and Py-GC analyseswas increased slightly as recycling number increase. After five cycles of recycling the ISO brightness of recycled handsheets dropped to about 90% of the original brightness. However, it had a gain of 10% in opacity. The most of physical properties of recycled handsheets were decreased as recycling numbers increase except of for tear strength.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.368-371
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• 2004

It analyzes the quality of the fine aggregate which is reproduced through a dry production process with cyclone and a wet production process. The conclusions of the study are as follows. 1. The recycled fine aggregate through the dry production process with cyclone shows the low rate of absorption and impurity content after the cyclone process. It shows that its density is 2.37, absorption rate is 4.8 and stability is $5.1\%$ and less. Therefore, it satisfies the standards of KS F 2573(recycled aggregate for concrete) as the first grade. 2. The recycled fine aggregate through the wet production process shows the low rate of absorption and foreign substance content after the process of wash and dehydration. It shows that its density is 2.40, absorption rate is 3.12 and stability is $3.2\%$ and less. Therefore, it satisfies the standards of KS F 2573(recycled aggregate for concrete) as the first grade.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.415-418
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• 2003

This study is performed to examine properties of polymer permeability concrete using recycled coarse aggregate and blast furnace slag for application of structures needed permeability. Tests for compressive strength, flexural strength and pulse velocity with replacement ratio of recycled coarse aggregate are performed. As a result, compressive strength, flexural strength and coefficient of permeability of polymer permeability concrete containing recycled coarse aggregate are in the range of $180{\sim}200kgf/cm^2,\;58{\sim}64kgf/cm^2\;and\;4.6{\times}10^{-2}{\sim}6.9{\times}10^{-2}cm/s$, respectively. Compressive strength, flexural strength and pulse velocity of polymer concrete containing crushed stone only are $192kgf/cm^2,\;65kgf/cm^2\;and\;6.1{\times}10^{-2}cm/s$, respectively. Accordingly, recycled coarse aggregate is expected that can be utilizing as an aggregate of polymer permeability concrete.

• Steel and Composite Structures
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• v.9 no.1
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• pp.19-38
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• 2009

The present paper provides test data to evaluate the seismic performance of recycled aggregate concrete (RAC) filled steel square hollow section (SHS) beam-columns. Fifteen specimens, including 12 RAC filled steel tubular (RACFST) columns and 3 reference conventional concrete filled steel tubular (CFST) columns, were tested under reversed cyclic flexural loading while subjected to constant axially compressive load. The test parameters include: (1) axial load level (n), from 0.05 to 0.47; and (2) recycled coarse aggregate replacement ratio (r), from 0 to 50%. It was found that, generally, the seismic performance of RACFST columns was similar to that of the reference conventional CFST columns, and RACFST columns exhibited high levels of bearing capacity and ductility. Comparisons are made with predicted RACFST beam-column bearing capacities and flexural stiffness using current design codes. A theoretical model for conventional CFST beam-columns is employed in this paper for square RACFST beam-columns. The predicted load versus deformation hysteretic curves are found to exhibit satisfactory agreement with test results.

• Magazine of the Korean Society of Agricultural Engineers
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• v.38 no.4
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• pp.137-146
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• 1996

This paper presents the results of field experience from an experimental pavement construction on a low volume road using recycled concrete. The recycled concrete was prepared by replacing a half of coarse aggregate with recycled aggregate. Virgin natural sand was used as fine aggregate together a plasticizer and a fly ash (0.8% and 5% by wt. of cement, respectively). The load bearing capacity of the subbase made of recycled aggregate was acceptable. The length, thickness and width of the pavement were l00m, 20cm and 3m, respectively. From construction experience, it was found that workability and finishability of the recycled concrete mixture were relatively poor, but strengths were satisfactory. Flexural strength, compressive strength and elastic modulus at 28 days were 54Kg/$cm^2$, over 250Kg/$cm^2$, and 220,OOOKg/$cm^2$, respectively. The construction could be performed by hand without much difficulty. The surface was finished smoothly by wet fabric and only minor cracks were found on the surface.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.1
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• pp.39-45
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• 2012

In this study, field test on utilization of recycled aggregates and crushed stone as horizontal drains to use an alternative material of sand in soft ground is practiced. The settlement with time showed similarly ranged from 28.4-30.3 cm in the all horizontal materials. The excess pore water pressure of the recycled aggregates and crushed stone showed smaller than sand. The small the excess pore water pressure becomes faster the consolidation period and it can reduces the amount of residual settlement. Therefore, it was verified as having enough to an alternative materials that the field applicability is excellent. The distribution of earth pressure with time showed similarly in the all horizontal materials. The recycled aggregates and crushed stone was very applicable to practice because there is no mat resistance in the horizontal drains layer. The penetration rate in the SCP and PVD improvement sections did not show large differences as the grain size and the horizontal drainage height increases.