• Magazine of RCR
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• v.18 no.3
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• pp.57-62
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• 2023

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.2
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• pp.97-102
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• 2011

Amount of disposed construction materials like waste concrete is growing fast and use of the recycled aggregate for concrete has been seriously considered. But the use of the recycled aggregate is very limited because recycled aggregate has very low quality. Therefore, quality of recycled aggregate is very important in the manufacturing of recycled aggregate concrete. We have studied a series of research according to chemical processes and investigate the alkaline elimination effect of recycled aggregate and quality variation of recycled aggregate by sodium carbonate. Thereafter we have evaluated quality of recycled fine aggregate and experimented quality of this aggregate. As a results, we find that it is easy to eliminate the calcium hydroxide in recycled aggregate by sodium carbonate and the quality of recycled aggregate increase by elimination of alkaline.

• Journal of the Korean Recycled Construction Resources Institute
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• v.2 no.1
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• pp.120-127
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• 2006

The hammer-milled characteristics of waste wood materials such as lumber, plywood, particleboard(PB), MDF and railroad tic were investigated in this study. The physical and mechanical properties of recycled boards according to types of recycled particle and the mixing ratios were also studied. The hammer-milled, waste wood materials had the dimensional distributions suitable for the core layer panicle. Bending strengths of recycled boards (one layer) were shown in order of plywood, PB(laboratory-fabricated with particles used in the PB factory), lumber, tego film-overlaid plywood, MDF, waste railroad tie, PB(factory-made) and LPL-overlaid PB. Cured resin and creosote containing waste wood contributed to dimensional stability of reconstituted boards. Considering the mixing effects between lumber and plywood with recycled PB particle, lumber particle was contributive to bending strength, MOE and internal bond(IB) strength, whereas plywood particle was contributive to dimensional stability. The bending and IB strength of 3 layer boards composing only recycled waste wood particles in core layer of board were in order of lumber, plywood, PB and MDF. On the other hand, the thickness swelling was in order of PB, lumber, plywood and MDF. Bending strength of the 3 layer boards mixed with recycled PB-particle in the core layer had a decreasing tendency, as the mixing ratios of recycled PB-particles increased. The dimensional stability of 3 layer recycled board was improved as the mixing ratio of recycled PB-particle increased same as in one layer. Formaldehyde emission of boards fabricated with recycled PB-particles in the core layer of the PB was in the range of E2 grade (below 5.0mg/l).

• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.2
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• pp.51-58
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• 2018

This study was a basic research for actual production of recycled aggregate concrete, and experiments were carried out on the change of water cement ratio and physical properties of recycled aggregate concrete with fixed slump. Results were as follows. Concrete using recycled aggregate were required increased water to maintain the target slump, and the recycled fine aggregate are necessary more increased water more than the recycled coarse aggregate. The replacement ratio of recycled fine aggregate be less than 60%, would be possible to obtain the air content volume that did not deviate from the concrete quality specification. The compressive strength of concrete using recycled aggregate decreased with increasing the replacement of recycled aggregate, and compressive strength decreased by 25% when 100% recycled fine aggregate were replaced. As a result of analyzing the correlation of compressive strength according to the mixing factors of concrete, it was found that replacement of recycled fine aggregate> water cement ratio> air content volume were influenced in order.

• Journal of the Korean Recycled Construction Resources Institute
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• v.12 no.2
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• pp.188-195
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• 2024

Recently, the use of recycled aggregates from construction waste has been introduced as a solution for environmental problems and aggregate shortage. In spite of the various methods to promote recycling of recycled aggregate, the use of recycled aggregate as the structural aggregate has been limited because the quality of recycled aggregate(especially recycled fine aggregate) has been considered lower than that of natural aggregate. In this work, recycled fine aggregate was immersed for an hour in acrylic resin solutions of various concentrations to improve its quality, the appropriate immersion concentration was selected by measuring the absorption capacity and skeletal density of the recycled fine aggregate, and mortar specimens were prepared to evaluate the mechanical performance in order to propose a applicable treatment process to promote the use of recycled fine aggregate. According to the experimental results, as the acrylic resin concentration increased, the absorption capacity and skeletal density of the recycled fine aggregate decreased. The absorption capacity was lowest at acrylic resin concentrations around 6 to 8 %. However, among mortar specimens made of recycled fine aggregate immersed in acrylic resin solution, the compressive strength was the highest at 4 % acrylic resin concentration, suggesting that the use of higher concentration acrylic resin solution can actually lower the compressive strength of mortar.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.199.1-199.1
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• 2010

Use of recycled aggregates that are constituents of concrete or asphalt-based structures has become popular because the recycling is an eco-friendly way to overcome the depletion of natural aggregates. In order to adopt the recycled aggregates for backfilling a power transmission pipeline trench, their thermal resistivity should be low enough to prevent thermal runaway in the transmission system. In this study, a series of laboratory tests with QTM-500 and KD2 Pro was performed to measure the thermal resistivity of recycled aggregates prepared from various sources. Relationships between the thermal resistivity of recycled aggregates and the water content have been obtained with consideration of compaction effort. Similar to natural soils, the thermal resistivity of the recycled aggregates decreases with increasing the water content. In addition, this study compared the experimental data with conventional prediction models for the thermal resistivity in the literature, which suggests the availability of the recycled aggregates as backfill material substituting for natural aggregates when backfilling the power transmission pipeline trench.

• Advances in concrete construction
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• v.9 no.1
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• pp.9-22
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• 2020

The present work looks at the possibilities of recycling more than once demolished concrete as coarse aggregates, to produce new concrete. Different concrete mixes were made with substitutions of 50%, 75% and 100% of recycled concrete aggregates respectively as coarse aggregates. The physico-mechanical characterization tests carried out on the recycled concrete aggregates revealed that they are suitable for use in obtaining a structural concrete. The resulting concrete materials had rheological parameters, compressive strengths and tensile strengths very slightly lower than those of the original concrete even when 100% of two cycles recycled concrete aggregates were used. The durability of the recycled aggregates concrete was assessed through water permeability, water absorption and chemical attacks. The obtained concretes were thought fit for use as structural materials. A linear regression was developed between the strength of the material and the number of cycles of concrete recycling to anticipate the strength of the recycled aggregates concrete. From the results, it appear clear that recycling demolished concrete represents a valuable resource for aggregates supply to the concrete industry and a the same time plays a key role in meeting the challenge for a sustainable development.

• Journal of the Korea Institute of Building Construction
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• v.7 no.4
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• pp.101-108
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• 2007

Furnace slag powder used currently in Korea needs to add special functions in response to the increase of large-scale projects. In addition, it is advantageous in that it has a lower hydration heat emission rate than ordinary Portland cement and improves properties such as the inhibition of alkali aggregate reaction, watertightness, salt proofness, seawater resistance and chemical resistance. However, furnace slag powder is not self -hardening, and requires activators such as alkali for hydration. Accordingly, if recycled fine aggregate, from which calcium hydroxide is generated, and furnace slag, which requires alkali stimulation, are used together they play mutually complementary roles, so we expect to use the mixture as a resource-recycling construction material. Thus the present study purposed to examine the properties and characteristics of furnace slag powder and recycled aggregate, to manufacture recycled fine aggregate concrete using furnace slag and analyze its performance based on the results of an experiment, to provide materials on concrete using furnace slag as a cement additive and recycled fine aggregate as a substitute of aggregate, and ultimately to provide basic materials on the manufacturing of resource-recycled construction materials using binder and fine aggregate as recycled resources.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.1231-1238
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• 2010

Recently, the utilization of recycled aggregates for backfilling a power transmission pipeline trench has been increasing due to the issues of eco-friendly construction and shortage of natural aggregate resource. It is important to investigate the physical and thermal properties of the recycled aggregates that can be used as a backfill material. This study presents the thermal properties of two types of recycled aggregates with various particle size distributions. The thermal properties of the recycled aggregate were measured using the transient hot wire method and the probe method after performing the standard compaction test using an automatic compactor. Similar to silica sand, the thermal resistivity of the recycled aggregates decreased when the water content increased. This study shows that the recycled aggregate can be a promising backfill material substituting for natural aggregate when backfilling the power transmission pipeline trench.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.05a
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• pp.61-64
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• 2005

Recently, there have been many studies about recycling cementitious powder from concrete waste(hereinafter referred to as waste powder), generated after recycle aggregate production. Previous studies showed that when the heating process of waste powder at $700^{\circ}C,\;Ca(OH)_2$ in paste is dehydrated making possible the restoration of hydraulic properties. Recycled cement with hydraulic properties restored is thought to be re-hydrated through the mechanism of hydration, which is almost similar in Portland cement. This clearly suggests that the hydrate of recycled cement is alkali in type. Like in general concrete, if recycled cement is used as a structural material, resistance performance against carbonation or neutralization by $CaCO_3$ in air probably would be most influential to the life of steel-reinforced concrete structure. Thus the purpose of this study is to make an experimental review on chemical properties of recycled cement, manufactured with concrete waste as base material, and investigate the durability of concrete using recycled cement through evaluating the cement s performance of resistance to carbonation in accordance with its accelerating age. Based on its results, further, the study seeks to provide basic information about ways of utilizing recycled cement.