• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.392-397
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• 1998

In this paper, the properties of cement mortar used recycled aggregate are analyzed and compared with river and crushed sand mortar. Recycled aggregates are made by crushing wasted concrete had various compressive strength, and test items are the properties of fresh mortar, hardened mortar and durability. According to the experimental results, flow, unitweight, strength and durability of cement mortar used recycled aggregates decrease compared with those of river and crushed sand mortar.

• KIEAE Journal
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• v.14 no.1
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• pp.131-138
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• 2014

The recent interests in securing alternative resource have increased due to environmental issues and exhaustion of natural resources. The government notices production of recycled aggregate using waste concrete as the substitute of the natural aggregate. However, It's important to reduce environmental burden being inevitably made in the process producing recycled aggregate. In this study, the scenarios of transportation distance were set in the transportation phase of production of recycled aggregate. In addition, The possibility of emissions and reduction of carbon dioxide were studied depending on the scenarios. For this study, data about a amount of waste concrete, transportation distance, kind of vehicle, the number of required vehicle, fuel efficiency of vehicle and etc were gathered from 15 companies of intermediate treatment and 60 constructions sites located in Daegu city and Kyungpook area. Based on those data, fuel consumptions and $CO_2$ emissions according to the transportation scheme of waste concrete were calculated. As a result of the study, the emission of carbon dioxide was possible to be reduced by 27.8~75.4% depending on the scenarios of transportation distance.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.305-306
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• 2023

Recently, as the radioactive waste disposal facility becomes scarce, the importance of efficient disposal of waste from nuclear power plants is increasing. This study was conducted to utilize radioactive waste concrete powder as solidifying agent for radioactive waste treatment. Paste with an age of more than one year was used with a disk mill to have a particle size of 150㎛ or less, and treated at temperatures of 500℃, 600℃ and 700℃ for 2 hours. In order to simulate the radioactive cement powder, aqueous solutions of Di-water, CsCl 1M, SrCl₂ 1M and CoCl₂ 1M were used as blending water at W/C 0.7 and to improve fluidity, polycarboxylate type superplasticizer was used at 0.4 wt.% based on the weight of recycled cement paste powder. Characterisation was carried out using vicat method, strength and density.

• Computers and Concrete
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• v.32 no.2
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• pp.173-184
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• 2023

In this study, mechanical, flexural post-cracking, and torsional behaviors of recycled steel fiber-reinforced concrete (RSFRC) incorporating steel fibers obtained from recycling of waste tires were investigated. Initially, three concrete mixes with different fiber contents (0, 40, and 80 kg/m³) were designed and tested in fresh and hardened states. Subsequently, the flexural post-cracking behaviors of RSFRCs were assessed by conducting three-point bending tests on notched beams. It was observed that recycled steel fibers improve the post-cracking flexural behavior in terms of energy absorption, ductility, and residual flexural strength. What's more, torsional behaviors of four RSFRC concrete beams with varying reinforcement configurations were investigated. The results indicated that RSFRCs exhibited an improved post-elastic torsional behaviors, both in terms of the torsional capacity and ductility of the beams. Additionally, numerical analyses were performed to capture the behaviors of RSFRCs in flexure and torsion. At first, inverse analyses were carried out on the results of the three-point bending tests to determine the tensile functions of RSFRC specimens. Additionally, the applicability of the obtained RSFRC tensile functions was verified by comparing the results of the conducted experiments to their numerical counterparts. Finally, it is noteworthy that, despite the scatter (i.e., non-uniqueness) in the aspect ratio of recycled steel fiber (as opposed to industrial steel fiber), their inclusion contributed to the improvement of post-cracking flexural and torsional capacities.

• Magazine of RCR
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• v.17 no.1
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• pp.15-21
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• 2022

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.901-904
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• 2006

The government makes efforts to expand the recycling activities of construction waste soil and to increase the usage of recycled aggregate. Accordingly, it has defined the compulsory usage and quality standard by usage of recycled aggregate. To satisfy these efforts requires both technology to produce recycled aggregate which meets the required quality and companies with the technology. Therefore, it requires to review a current status of facilities at the companies which deal with construction wastes. The companies dealing with construction wastes gradually produce the high quality of recycled aggregate. In particular, companies which has over 3-stage processing system for waste concrete continue to increase and means to remove foreign substances are gradually improved.

• Journal of Construction Engineering and Project Management
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• v.3 no.1
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• pp.28-34
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• 2013

Use of recycled aggregates in portland cement concrete (PCC) construction can offer benefits associated with both economy and sustainability. Testing performed to date indicates that recycled brick masonry aggregate (RBMA) can be used as a 100% replacement for conventional coarse aggregate in concrete that exhibits acceptable mechanical properties for use in structural and pavement elements, including satisfactory performance in some durability tests. Recycled brick masonry aggregate concrete (RBMAC) is currently not used in any type of construction in the United States. However, use of RBMAC could become a viable construction strategy as sustainable building practices become the norm. This paper explores the feasibility of use of RBMAC in several types of sustainable construction initiatives, based upon the findings of previous work with RBMAC that incorporates RBMA produced from construction and demolition waste from a case study site. A summary of material properties of RBMAC that will be useful to construction professionals are presented, along with a discussion of advantages and impediments to use. Several quality assurance and quality control techniques that could be incorporated into specifications are identified.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.529-532
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• 2006

In this study, recently it has to be solved urgently the unbalance of demand and supply about the fine aggregate because the sea sand is restricted by exhaustion of river sand and intensification of environmental law. In this background, manufacturing technology which can produce recycled sand from construction and demolition waste concrete mass is developed. However, the existed washing method has the problem which not only impurities but also many other things make poor quality. Therefore, it tries to conform in time necessity, the objective of this study is to develop the Sand Flux system which can product the high-quality recycled sand from wast concrete and high value-added technology of the high-quality recycled sand as basic materials for mortar and concrete. At the same time it will be able to improve the quality of recycled sand products as an experiment of the physical nature and a quality present condition the products of recycled sand from construction waste.

• International Journal of Concrete Structures and Materials
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• v.8 no.2
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• pp.165-172
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• 2014

Recycled coarse aggregate (RCA) made from waste concrete is not a suitable structural material as it has high absorption of cement mortar, which adheres on the aggregate surface and on the tiny cracks thereon. Therefore, when using RCA made from waste concrete, much water must be added with the concrete, and slump loss occurs when transporting. Hence, its workability is significantly worse than that of other materials. In this study, surface of RCA was coated with water-soluble polycarboxylate (PC) dispersant so that its characteristics improved. Each possibility was evaluated: whether its slump loss can be controlled, by measuring its workability based on the elapsed time; and whether it can be used as a structural material, by measuring its strength. Moreover, the carbonation due to cement mortar adhesion was measured through a carbonation test. As a result, RCA coated with PC dispersant was found to be better than crushed coarse aggregate and RCA when the physical properties of the fresh concrete and the mechanical, durability of the hardened concrete were tested.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.11a
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• pp.569-572
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• 2003

In many countries a considerable amount of demolition wastes is generated and wastes concrete constitutes a significant proportion of the construction waste. Therefore, the necessity for the use of recycled aggregate in concrete arise and the reuse of a waste concrete may solve the problems of environmental pollution and shortage of natural aggregate. According to this study is to examine the possibility of site adoption microwave-use early strength estimation method. Based on the existed study related the plain concrete, the interrelation between recycled aggregate concrte and microwave-use early strength estimation method is required.