• Journal of The Korean Society of Agricultural Engineers
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• v.58 no.1
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• pp.19-26
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• 2016

This study was performed to evaluate the strength and durability properties of modified epoxy composites with waste tire chip, recycled coarse aggregate, filler and modified epoxy to improve elongation and elasticity of epoxy. Additionally, for comparing to modified epoxy and unsaturated polyester resin as a binder, unsaturated polyester resin composites were developed in the same condition. The mix proportions were determined to satisfy the requirement for the workability and slump according to aggregate size and binder content. Tests for the compressive and flexural strength, freezing and thawing and durability for 20 % sulfuric solution were performed. The compressive and flexural strength of modified epoxy composites were in the range of 34.9~61.6 MPa and 10.2~18.3 MPa at the curing 7 days, respectively. Also, the compressive and flexural strength of unsaturated polyester resin composites were in the range of 44.2~77.8 MPa and 11.3~20.8 MPa at the curing 7 days, respectively. After 300 cycles of freezing and thawing, weight decrease ratio and durability factor of modified epoxy composites were in the range of 0.8~1.9 % and 95~98, respectively. Accordingly, modified epoxy composites will greatly improve the durability of concrete.

• Advances in concrete construction
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• v.10 no.6
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• pp.537-546
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• 2020

Exterior walls in buildings are exposed to various forms of thermal loads, which depend on the positions of walls. Therefore, one of the efficient methods for improving the energy competence of buildings is improving the thermal properties of insulation plaster mortar. In this study, lightweight fine aggregate (LWFA) and micro rubber ash (MRA) from recycled tires were used as partial replacements for sand. The flow ability, unit weight, compressive strength, tensile strength, thermal conductivity (K-value), drying shrinkage and microstructure scan of lightweight rubberized mortar (LWRM) were investigated. Ten mixtures of LWRM were prepared as follows: traditional cement mortar (control mixture); three mixes with different percentages of LWFA (25%, 50% and 75%); three mixes with different percentages of MRA (2.5%, 5% and 7.5%); and three mixes consisting both types with determined ratios (25% LWFA+5% MRA, 50% LWFA+5% MRA and 75% LWFA+5% MRA). The flow ability of the mortars was 22±2 cm, and LWRM contained LWFA and MRA. The compressive and tensile strength decreased by approximately 64% and 57%, respectively, when 75% LWFA was used compared with those when the control mix was used. The compressive and tensile strength decreased when 5% MRA was used. By contrast, mixes with determined ratios of LWFA and MRA affected reduced unit weight, K-value and dry shrinkage.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.91-98
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• 2009

Recently, production cost of ready mixed concrete has been increased due to the rising cost of raw materials such as cement and aggregate etc. cause by the upturn of oil price and increase of shipping charge. The delivery cost of ready mixed concrete companies, however, has been decreased owing to their excessive competition in sale. Consequently, ready mixed concrete companies began to manufacture the concrete by mixing ground granulated blast furnace slag(GGBF) and fly-ash in order to lower the production cost. Therefore, the objective of this study was to predict 28 days strength of GGBF slag concrete by early strength(warm and hot water curing method) for the sake of managing with ease the quality of ready mixed concrete. In experimental results, the prediction equation for 28 days compressive strength of GGBF slag concrete could be produced through the linear regression analysis of early strength and 28 days strength. In order to acquire the reliability, all mixture were repeated as 3 times and each mixture order was carried out by random sampling. The prediction equation for 28 days strength of GGBF slag concrete by 1 day compressive strength(accelerated testing) according to warm and hot water curing method won the good reliability.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.103-110
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• 2011

This study is to comparatively analyze the characteristics of pH decrease in recycled fine aggregates for embankment and landfill produced from waste concrete by using natural process and artificial process. The result was as follows In case of recycled fine aggregates left outdoor, it was found that pH level was decreased if the thickness of embankment becomes thinner, or the materials left outdoors owing to high concentration of $CO_2$ in atmosphere caused by respirations of people. When the air was permeated, pH level was decreased more effectively. It was analyzed that this phenomenon was caused by efficient supply of $CO_2$ in the recycled fine aggregates owing to high-pressure ventilators. In case of water spraying treatment, sprayed water facilitated hydration of unhydrated cement to dissolve calcium hydroxides which neutralized $CO_2$ in the atmosphere during desiccation process and decrease pH level by a considerable margin. In case of Immersed treatment, decrease of pH was not sufficient. When facilitating the supply of $CO_2$, pH level of the recycled fine aggregates was decreased by the largest margin. It was analyzed that this phenomenon was caused by efficient supply of $CO_2$. From the above results, it was analyzed that the most effective method of reducing pH level of the recycled fine aggregates from the aspects of pH reduction performance, economic efficiency and workability was repeated wet-dry cycles of spraying water to the aggregates in the proportion of 1:0.5 by weight and then treating by forcefully blowing $CO_2$ gas into the aggregates.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.2
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• pp.84-90
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• 2012

Patents in Korea, Japan and the U.S. were searched at the Korea Intellectual Property Rights Information Service (KIPRIS) of Korea Institute of Patent Information using related keywords in order to analyze the trend of patents on the usage of waste wood. Materials on a total of 77 patents in Korea, 317 patents in Japan, and 316 patents in the U.S. that had been registered as patents as of Dec. 31, 2011 were collected. Among the collected materials, the patents rejected, expired, annulled, withdrawn and waived as well as those which had little relationship with waste wood were excluded and the 71 patents in Korea, 227 patents in Japan and 216 patents in the U.S. were finally selected for analysis. In addition, the properties of the mortar which used waste wood as an alternative for a part of the fine aggregate were tested as a basic study for the usage of waste wood as a lightweight aggregate for concrete. For the test, the waste wood of the pine tree was crushed, sifted through No. 8(2.4 mm) sieve, and then dried for 24 hours at $100{\pm}5^{\circ}C$. As it is known that some kinds of tree prevent the hardening of cement when the wood is mixed with cement, the crushed waste wood in this study was dipped in the water of $20^{\circ}C$, $50^{\circ}C$, $80^{\circ}C$ and $100^{\circ}C$ and then dried up before testing the properties of the mortar to examine the effect of the preliminary treatment of crushed waste wood.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.4
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• pp.425-432
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• 2023

In this study, we aim to develop a carbon-reducing concrete technology by incorporating biochar. Performance evaluation experiments were conducted on concrete mixtures containing biochar with insulating and carbon-capturing properties, which are essential for key infrastructure sectors such as construction and tunnels. Concrete mixtures were designed with different biochar incorporation rates of 0 %, 5 %, 10 %, 15 %, and 20 %, as w ell as w ater-to-binder ratios of 0.25, 0.30, 0.35, and 0.40. To assess the physical properties of each mixture, unit weight, total porosity, and permeability were measured, while mechanical properties were determined through the measurement of concrete compressive and flexural strengths. Key factors for enhancing the insulating effect of carbon-reducing concrete containing biochar were identified through regression analysis, indicating a close correlation among biochar incorporation rate, unit weight, concrete strength, and thermal conductivity. It is anticipated that it can be utilized as an insulating material to enhance thermal performance in northern regions with severe winter climates.

• 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.

• Journal of the Korea Concrete Institute
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• v.24 no.4
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• pp.465-472
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• 2012

This research aims to find an effective mixing method for controlled low strength material (CLSM) using diverse recycled industrial byproducts. This study is a fundamental research to develop and commercialize a resource-recycling CLMS that can greatly contribute to cost reduction and environmental stress relief. In the past, few studies have been performed on CLSM in Korea. This research is expected to provide fundamental data not only for development and commercialization of the resource-recycling CLSM satisfying required material performances but also serve as a ground breaking study on utilization of recycled material in construction industry and ultimately leading to advanced resource-recycling practices at national level. From the comprehensive analysis of minimum unit quantity for maximum strength and material segregation prevention, it was found that the optimal mixing condition for mixing FSD, RSID and SD material to filler-aggregate ratio (f/a) was approximately 50.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.275-282
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• 2018

This study examines the ways to address environmental issues by utilizing activated loess to reduce the amount of cements that emit a large amount of carbon dioxide during the process of manufacturing, and by reusing the polysilicon sludge produced as a result of manufacturing polysilicon, one of the components for solar power generation panels. The findings of the experiment showed that the optimal replacement ratio of the polysilicon sludge is 20%, 35% for W/B, and 20% for the ratio of the fine aggregate addition. As it is deemed that utilizing the polysilicon sludge for reinforced concrete may lead to rebar corrosion due to the $CI^-$ contained in the sludge, it can be considered to use for unreinforced concrete or bricks.

• Computers and Concrete
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• v.26 no.6
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• pp.467-482
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• 2020

This research focused on analyzing the post-fire behavior of high-performance concrete-filled steel tube (CFST) columns, with the concrete containing tire rubber and steel fibers, under axial compressive loading. The finite element (FE) modeling of such heated columns containing recycled aggregate is a branch of this field which has not received the proper attention of researchers. Better understanding the post-fire behavior of these columns by measuring their residual strength and deformation is critical for achieving the minimum repair level required for structures damaged in the fire. Therefore, to develop this model, 19 groups of confined and unconfined specimens with the variables including the volume ratio of steel fibers, tire rubber content, diameter-to-thickness (D/t) ratio of the steel tube, and exposure temperature were considered. The ABAQUS software was employed to model the tested specimens so that the accurate behavior of the FE-modeled specimens could be examined under test conditions. To achieve desirable results for the modeling of the specimens, in addition to the novel procedure described in this research, the modified versions of models presented by previous researchers were also utilized. After the completion of modeling, the load-axial strain and load-lateral strain relationships, ultimate strength, and failure mode of the modeled CFST specimens were evaluated against the test data, through which the satisfactory accuracy of this modeling procedure was established. Afterward, using a parametric study, the effect of factors such as the concrete core strength at different temperatures and the D/t ratio on the behavior of the CFST columns was explored. Finally, the compressive strength values obtained from the FE model were compared with the corresponding values predicted by various codes, the results of which indicated that most codes were conservative in terms of these predictions.