• Journal of the Korea Concrete Institute
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• v.17 no.1 s.85
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• pp.69-76
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• 2005

In this study, the high qualify recycled fine aggregate manufacturing system by the drying specific gravity separation method was evaluated. For the evaluation of the performance of the recycled aggregate, the engineering properties and durability of recycled aggregate has been tested. From the test results, the quality of recycled fing aggregates was improved by high quality recycled fine aggregate manufacturing system and satisfied with the quality standards of KS and JASS 5. Also, compressive and tensile strengths of recycled concrete show no critical difference caused by recycled fine aggregate replacement ratio. However, durability such as carbonation depth chloride ion penetration depth and drying shrinkage shows more deterioration than the concrete without recycled fine aggregate

• 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 the Korean Recycled Construction Resources Institute
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• v.3 no.3
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• pp.277-282
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• 2015

This study is conducted to utilize waste concrete powder (WCP) made as a by-product manufacturing high quality recycled aggregate. The blaine fineness of the used waste concrete powder was $928cm^2/g$. As the main characteristic of waste concrete powder, it showed an angular type similar to cement, but hydrated products were attached on the surface of particles. In addition, the size of the particles of waste concrete powder was larger than OPC and in terms of chemical components it had higher $SiO_2$ contents. For using WCP in soil cement-based pavement, the qualities, physical and chemical properties, of WCP should be researched. In the first step, the specified compressive strength of mortar for two types of clay sand soil and clay soil respectively was experimented to be 15 MPa and then optimum mixing ratio of chemical solidification agent were decided in the range of 1.5 - 3.0% in the replacement with cement weight content. In the second step, based on the prior experimental results, recycling possibility of WCP in soil cement-based pavement was studied. In the result of experiment the mixing ratio of WCP were 5, 10, 15 and 20% in the replacement with soil weight and the compressive strength of mortar was somewhat decreased according to the increase of the mixing ratio of WCP.

• Journal of the Korea Institute of Building Construction
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• v.15 no.2
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• pp.193-199
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• 2015

As a solution of both environmental issue of reducing carbon dioxide emission and sustainable issue of exhausting natural resources, in concrete industry, many research on recycling various by-products or industrial wastes as the concrete materials has been conducted. The aim of this research is feasibility analysis of additional reaction with ordinary Portland cement and flue gas desulfurization gypsum based on the blast furnace slag and recycled fine aggregate based mortar to achieve the normal strength range. Consequently, in the case of mortar replaced 10% FGD and 30% OPC for BS, 80% of plain OPC mortar's compressive strength was achieved. Furthermore, when the water-to-binder ratio is decreased to keep the practically similar level of flow, it is expected to be achieve the equivalent compressive strength to plain OPC mortar.

• International Journal of Highway Engineering
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• v.3 no.2 s.8
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• pp.103-112
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• 2001

This study was performed to evaluate applicability of recycled aggregates as subbase and surface concrete materials for cement concrete pavement. Laboratory compaction test, CBR test and plate load bearing test were conducted to evaluate applicability for pavement subbase materials. Recycled concrete for surface course was manufactured with a design strength of $280kgf/cm^2$. Normal coarse aggregate was substituted with recycled aggregates with five different ratios, 0%, 20%, 40%, 60% and 80% for recycled concrete mixes. Fresh concrete Properties, concrete strength properties for the five substitution percentages of recycled aggregates after 28-day curing and freezing-and-thawing resistance were evaluated experimentally. Based on the experimental results, it was concluded that the recycled aggregate was the material good enough to use for subbase material, and 40% or lower substitution ratio was an appropriate percentage of recycled aggregates replacement for surface concrete.

• Journal of the Korea Concrete Institute
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• v.24 no.2
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• pp.157-164
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• 2012

This study evaluates the shear performance of reinforced concrete beams with recycled coarse aggregates. A total of six specimens with various replacement ratios of recycled coarse aggregates (0%, 50%, and 100%) and different amount of shear reinforcement were cast and tested in this study. A finite element analysis was performed to predict the shear behavior of the specimens with natural or recycled coarse aggregates. The FE analysis was performed using a two-dimensional nonlinear FE analysis program based on the disturbed stress field model (DSFM), which is an extension of the modified compression field theory (MCFT). Experimental results showed that the specimens with 50% and 100% replacement ratios of recycled coarse aggregates had the similar shear strength compared to the specimen with natural aggregates, regardless of the replacement ratios of recycled coarse aggregates and the amount of the shear reinforcement. Furthermore, the comparison between experimental and analytical results showed that the proposed numerical modeling methods and the analytical model, DSFM, can be successfully used to predict the shear behavior of reinforced concrete beams with recycled coarse aggregates.

• Journal of the Korea Institute of Building Construction
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• v.12 no.5
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• pp.548-557
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• 2012

In this study the thermal performance of G-PCM replaced for find aggregate in mortar specimens was evaluated using TG-DTA. As a result, it was found that when solid changed into liquid, it absorbed heat, and when liquid changed into solid, it radiated heat. In addition, the fluidity and the compressive strength of mortar with G-PCM can be applied to the floor mortar and a wall finish material. Also the higher the replacement ratio, the larger the latent heat capacity. It was found that the mortar with G-PCM slowed the increase and decrease of temperature. Thus, the duration of pleasant indoor temperature is extended by the floor and wall mortar with G-PCM. In conclusion, G-PCM is expected to reduce the heating energy consumption.

• Computers and Concrete
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• v.19 no.6
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• pp.617-623
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• 2017

This work is conducted with the aim of using waste material to reserve the natural resources. The objective is accomplished by conducting experimentation and verify by modeling based on fuzzy logic. In experimentation, concrete is casted by using natural/river sand as fine aggregate and termed as control specimen. Natural sand is conserved by replacing it with used foundry sand (UFS) by an amount of 10, 20 and 30% by weight. Fresh and hardened properties of concrete are investigated at different ages. It is observed that compressive strength and modulus of elasticity reduced with the increase in amount of UFS. Furthermore, concrete compressive strength is predicted by using fuzzy logic model and verified at different replacement ratio and age with experimental observations.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.465-468
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• 2005

This Study is concerned workability and the physical properties for practical use of waste concrete powder originated from the manufacturing progress of waste concrete aggregate and it apply to concrete tile. Also because it is important that concrete tile has to ensure the surface moisture stability, for solving the problems aplied curing method is air-dried and autoclave curing. As the result, the physical properties, such as fluent properties, compressive strength, surface hardness and surface glossiness, were decreased with increase of replacement ratio of waste concrete powder, also surface stability was weaked about moisture. But by autoclave curing, it is possible that compressive strength and surface hardness increased, and surface moisture stability is ensured.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.521-524
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• 2011

본 논문에서는 순환골재에 대하여 구조용 적용성 검증을 목표로 하였으며, 천연골재와 순환골재 치환율에 따른 압축파괴강도와 압축강도증가에 따른 파속도의 상관관계를 비교 분석하였다. 설계기준강도 21, 27, 35MPa에 순환굵은골재 치환율 0, 30, 50, 100%를 적용하여 설계기준강도에 따른 순환굵은골재 치환율의 배합을 총 12가지로 설정하였다. 재령160일까지의 압축파괴강도의 변화를 대기양생 공시체, 수중 양생공시체 그리고 코어공시체를 이용하여 비교하였고, 모의부재(800${\times}$800${\times}$200mm)를 통하여 재령160일까지의 초음파속도를 측정하였다. 압축파괴실험을 통하여 취득한 데이터를 비교해 본 결과 순환굵은골재 치환율에 따른 강도저하현상은 나타나지 않았다. 또한, 재령일에 따른 강도 증가와 함께 파속도도 같이 증가함을 알 수 있었다.