• Horticultural Science & Technology
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• v.18 no.4
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• pp.523-528
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• 2000

Plug seedlings of Petunia hybrida 'Madness Rose' and Viola tricolor 'Magestic GT' were cultured in media containing various volume ratios of recycled plug medium, recycled coir, perlite, granular rockwool, and vermiculite for 36 and 43 days after sowing, respectively. Recycled plug medium and recycled coir were steam pasteurized for 30 minutes at $120^{\circ}C$ and 1.5 atmosphere. An unused commercial plug medium (Tosilee, pH 5.10, EC $0.12mS{\cdot}cm^{-1}$ at 1:5 dilution, v/v, Shinan Grow Co.) was used as the control. The pH of different media before and after growing seedlings was similar. Medium EC was high when recycled plug medium was included. Recycled coir (75%)＋vermiculite (25%) mixture also had high medium EC. However, medium EC was low when granular rockwool or perlite was included. Height, root formation, shoot dry weight and leaf count (ea) of petunia, and height, total fresh and dry weights, and shoot fresh and root dry weights of pansy were the highest in recycled coir (75%)＋perlite (25%) mixture. Recycled coir was better than recycled plug medium in physicochemical properties, and also in resultant plant growth. It is recommended to include perlite or granular rockwool when plug media including recycled horticultural media are prepared.

• Journal of the Korean Geotechnical Society
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• v.27 no.7
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• pp.17-33
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• 2011

Recently, the utilization of recycled aggregates for backfilling a power transmission pipeline trench has been considered due to the issues of eco-friendly construction and a lack of natural aggregate resource. It is important to identify the physical and thermal properties of domestic recycled aggregates that can be used as a backfill material. This paper evaluated thermal properties of concrete-based recycled aggregates with various particle size distributions. The thermal properties of the recycled aggregates and river sand provided by local vendors were measured using the transient hot wire method and the transient needle probe method after performing the standard compaction test. The needle probe method considerably overestimated the thermal resistivity of recycled aggregates especially at the dry of optimum water content because of experiencing disturbance while the needle probe is being inserted into the specimen. Similar to silica sand, the thermal resistivity of recycled aggregates decreased when the water content increased at a given dry density. Also, this paper evaluated some of the existing prediction models for the thermal resistivity of recycled aggregates with the experimental data, and developed a new prediction model for recycled aggregates. This study shows that recycled aggregates can be a promising backfill material substituting for natural aggregates when backfilling the power transmission pipeline trench.

• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.613-620
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• 2005

There are some problems in utilizing recycled concrete aggregate go structural use because of the difficulties concerning about quality control and durability. It seems to be possible to utilize recycled concrete aggregate for making concrete products because quality control of concrete products is easier than ready-mixed concrete, but there are little studies about the properties of the steam-cured recycled aggregate concrete. In this study, various tests were performed such as compressive strength, flexural strength, splitting tensile strength, bonding strength and chloride ion penetration test to evaluate the effect of substitution of recycled concrete aggregate. The results of strength test showed that the concrete strength decreased with the increase of the substitution ratio of recycled concrete aggregate, but it was in the reasonable range and almost equal to that of normal concrete below the substitution ratio of $50\%$. On the other hand, strength test of furnace slag cement concrete shows that the strength of recycled concrete with furnace slag cement under curing condition lower than that of recycled concrete with ordinary portland cement under same condition. From the result of this study, it can be concluded that recycled concrete aggregate is able to be utilized for structural use but substitution ratio should be decided with care in each case. The result of this study could be used as the basic data for the structural use of recycled concrete aggregate.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.2
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• pp.132-139
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• 2015

In this study, the different unit cement content by the ratio of water absorption and water-cement ratio are applied to examine the properties of the concrete used the aggregate recycled by the crushing treatment. According to the experimental results, in the mix of low strength and high water-cement ratio, both of the compressive strength is almost equal in the concrete using the recycled aggregate by the crushing treatment and the concrete using broken stones. It means that the recycled aggregate has the low effect of the amount of bonded mortar. But, in the mix of high strength and low water-cement ratio, the concrete using the recycled aggregate by the crushing treatment has 40% less of the compressive strength than that using broken stones by the effect of the amount of bonded mortar. On the other hand, after 8 weeks, the dry shrinkage of the recycled aggregate with 7% of the ratio of water absorption doubles that of the broken stones with 1% ($-350{\times}10^{-6}$), in other words $-700{\times}10^{-6}$. Thus, the dry shrinkage should be prior to any other conditions in recycling waste concrete for the aggregate for concrete. When the recycled aggregate with 3% of the ratio of water absorption is used, the compressive strength of the rich mix concrete ($450kg/m^3$ of the unit cement content) is equivalent to that of the concrete using broken stones, while in using the recycled aggregate with 7% of the ratio of water absorption, the rich mix concrete has 7% lower compressive strength than the concrete using broken stones. But, the compressive strength of the ordinary mix concrete ($350kg/m^3$ of the unit cement content) is far lower than that using broken stones.

• Journal of the Korea institute for structural maintenance and inspection
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• v.24 no.3
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• pp.63-69
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• 2020

The volume of construction waste material from the entire waste material volume in Korea is approximately 47.3% to take the biggest ratio, and from them, the waste concrete takes up approximately 62.8% that recycling is an urgent issue to address. Therefore, the government recommends more diverse and broader facilitation of the recycled aggregate in order to promote recycling the construction waste materials. In addition, when using concrete recycled aggregate in building, building standard such as floor area ratio and building height are being mitigation. The standard is a condition that mitigation the floor area ratio by up to 15% when using up to 25% of concrete recycled aggregate. Therefore, this study reviewed the relaxation of construction of construction standards when using concrete recycled aggregate in order to actively recommend the use of concrete recycled aggregate. And using the recycled coarse aggregate among the recycled aggregate, the appropriate mixing time in the batch plant according to the substitution rate was derived. In addition, using recycled aggregate admixture in order to improve the drying shrinkage, did comparative analysis about physical and mechanical property of concrete.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.490-497
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• 2020

This work has been initiated to find possibility whether recycled fine aggregate can be used as a source of aggregate for structural concrete or not. Two-stage mixing approach was chosen in order to maximize strength potential from recycled fine aggregate. Moisture content of the recycled fine aggregate was changed, and two different types of two-stage mixing approaches were applied to produce cement mortar. The strength of mortar made of 100% recycled fine aggregate by two-stage mixing approaches was compared to that of mortar made of 100% washed sea sand. According to the results, the effect of moisture content on compressive strength was observed from low water cement mortar(W/C 0.3). In case of W/C 0.5 cement mortar, no clear relationship was observed between moisture content and strength development. It was found that two-stage mixing approach has a potential to increase the strength of mortar made of 100% recycled fine aggregate. In case of modified version of two-stage mixing approach which first prepares cement paste and pours recycled fine aggregate into the cement paste, was more effective to increase the strength of mortar made of 100% recycled fine aggregate.

• Journal of the Korean Chemical Society
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• v.67 no.6
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• pp.420-428
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• 2023

Crosslinking was introduced into vinylized-mesoporous silica and recycled polyethylene. By introducing a vinyl group into the mesoporous silica, it becomes a material capable of inducing cross-linking with non-polar polyethylene. By synthesizing vinylized-mesoporous silica and inducing crosslinking with recycled polyethylene, a recycled polyethylene composite with improved physical properties than existing recycled polyethylene was synthesized. In addition, even when a small amount is added according to the grade of recycled polyethylene using vinylized-mesoporous silica, the crosslinking reaction proceeds and all physical properties are improved. Four types of vinylized-mesoporous silica were synthesized, and the shape, microstructure, and functional groups were analyzed by TEM, BET, FT-IR, and XRD. Using vinylized-mesoporous silica, three types of compounds were blended by crosslinking reaction with recycled polyethylene. In order to confirm the presence or absence of crosslinking, analysis was performed using XPS and FT-IR, and physical properties such as tensile strength, elongation, flexural strength, and flexural modulus were confirmed using a universal testing machine. As a result, by applying vinylized-mesoporous silica to recycled polyethylene in various grades, the weak physical properties of existing recycled polyethylene were overcome. By applying the vinylized-mesoporous silica, recycled polyethylene composite material that overcomes the weak physical properties to the normal polyethylene, it shows the optimal physical property index that can be used commercially. Therefore, it is expected that it can potentially increase the use of recycled polyethylene and recycle resources.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.45 no.3
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• pp.20-26
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• 2013

We investigated practical methods of using recycled gypsum board paper in the paper industry. Gypsum board paper is used to produce construction gypsum board, and can be recycled through the recycling process of construction wastes. The experiments were carried out in two ways: One was the substitution of recycled gypsum board papers for KOCC, and the other was the use of recycled gypsum board paper powder. Recycled gypsum board paper was not disintegrated easily, but high temperature and the use of chemicals were able to improve their disintegration. The physical properties of handsheets made of the pulp of recycled gypsum board paper exhibited the same performance level as those made from KOCC except in the parameter of compressive strength. The powder of recycled gypsum board paper was manufactured using a grinder and handsheets were made with the powder and KOCC. The bulk was increased, but the strength properties were decreased by the addition of the powder.

• Journal of the Korea Concrete Institute
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• v.16 no.4 s.82
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• pp.541-548
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• 2004

This study peformed an evaluation of the physical and mechanical properties and sound absorption characteristics of porous concrete according to the target void ratio and content of the recycled aggregate in order to reduce the noise generated in roads, railroads, residential areas and downtown areas and effectively utilize the recycled waste concrete aggregate generated as a byproduct of construction. The test results demonstrated that the difference between the target void ratio and the actual measured void ratio was less than 1.7% and that the tendency of the compression strength was to reduce rapidly when the target void ratio and the content of the recycled aggregate exceeded 25% and 50%, respectively. In addition, the sound absorption characteristics of the porous concrete using recycled waste concrete aggregate showed that the NRC was the highest at the target void ratio of 25% and the content of the recycled aggregate had very little influence on the NRC. Therefore, when considering the compression strength and the sound absorption characteristics of porous concrete, the proper target void ratio and the content of the recycled waste concrete aggregate are thought to be 25% and 50%, respectively

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.8-15
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• 2018

Waste concrete accounts for the largest portion of construction waste, and the supply of natural aggregate is unstable. Therefore, importance of using recycled aggregate is emphasized. The purpose of this study is to investigate the mechanical properties of high strength concrete according to the replacement rate of recycled coarse aggregate. For this purpose, the target design compressive strength was set to 40MPa, and the substitution rates of the recycled coarse aggregate were set to 0%, 30%, 60%, and 100%, respectively. Through experiments on the unreinforced concrete and hardened concrete, The validity of the use was confirmed. In addition, LCA method was used to evaluate the environmental impact of recycled aggregates and to compare and analyze the environmental impacts of the aggregates.