• Advances in concrete construction
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• v.16 no.6
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• pp.303-316
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• 2023

Using industrial wastes and construction and demolition (C&D) wastes is potentially advantageous for concrete production in terms of sustainability improvement. In this paper, a sustainable Self-Compacting Concrete (SCC) made with industrial wastes and C&D wastes was proposed by considerably replacing natural counterparts with recycled coarse aggregates (RCAs) and supplementary cementitious materials (SCMs) (i.e., Fly ash (FA), ground granulated blast furnace slag (GGBS) and silica fume (SF)). A total of 12 SCC mixes with various RCAs and different combination SCMs were prepared, which comprise binary, ternary and quaternary mixes. The mechanical properties in terms of compressive strength and static elasticity modulus of recycled aggregates (RA-SCC) mixes were determined and analyzed. Microstructural study was implemented to analyze the reason of improvement on mechanical properties. By means of life cycle assessment (LCA) method, the environmental impacts of RA-SCC with various RCAs and SCMs were quantified, analyzed and compared in the system boundary of "cradle-to-gate". In addition, the comparison of LCA results with respect to mechanical properties was conducted. The results demonstrate that the addition of proposed combination SCMs leads to significant improvement in mechanical properties of quaternary RA-SCC mixes with FA, GGBS and SF. Furthermore, quaternary RA-SCC mixes emit lowest environmental burdens without compromising mechanical properties. Thus, using the combination of FA, GGBS and SF as cement substitution to manufacture RA-SCC significantly improves the sustainability of SCC by minimizing the depletion of cement and non-renewable natural resources.

• Korean Institute of Interior Design Journal
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• v.15 no.6 s.59
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• pp.172-177
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• 2006

Most of the Korean multi-dwelling houses have less than 20 years of lifespan. Because the environmental issues such as energy consumption, limited resources, and demolition waste problems became been more and more critical, we now need to focus on long lasting and adaptable buildings. Korean wall bearing apartment buildings are constructed with site cast concrete for core, exterior, and interior together with pipes varied, so when the buildings are old and life style of the users changes, it is difficult to maintain and renovate these buildings. In this study, to resolve the problems described above, two types of Korean long life multi-dwelling housing models which represent improved durability and adaptability responding user's needs and life style changes were proposed with various methods as follows: Either column and beam structure or flat slab structure was used to utilize space better. To make maintenance easier and renovation economical for both public space and each unit, plumbing pipes, ducts, and conduits were clustered at the cores and public corridors with access doors and light weight partitions with steel studs and raised floors or above-ceiling spaces were used in lieu of site cast concrete walls and floor slabs with varied pipes.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.2
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• pp.19-30
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• 2012

Due to the fact that the social environment is improved and the urban development is stabilized, the demand of new construction of apartment becomes slowdown. Accordingly, there are many researches to lengthen the service life of the existing apartment through the remodeling and its importance is continuously rising. However, reliable design specifications and guidelines for the design of remodeling with partial demolition are not provided yet in Korea. Specially, in the apartment remodeling, slab collapse accidents take major portion in all accidents that reported by Korean Government. It is very important to prevent intial crack of slab because intial crack could cause severe accident like collapse of all structure in a short period of time. The purpose of this study is to develop structural guidelines that could guarantee the structural safety and serviceability of slab structure and could be adopted in Korean remodeling with partial demolition. There are mainly two components to determine structural behavior of slab structure. One is the shape of slab structure and the other is load which is resisted by the slab structure. In this study, the weight per unit volume of concrete debris and concrete strength are estimated through the analysis of previous researches to recognize the relationship between the shape of slab and load that loaded on the slab. Accordingly, approximately 300 pieces of floor plan are collected and analyzed. The finite element analysis is conducted using these analyzed and estimated results. From the finite element analysis results, the limited stacking height of debris is suggested and the stacking method is also discussed. In addition, to find the relationship between movement of demolition equipment and structural behavior of slab, the static and dynamic loading tests are conducted. From the results of loading tests, the impact factor which will be considered in the remodeling design could be estimated.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.33 no.3
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• pp.317-331
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• 2023

Objectives: Construction workers are exposed to various hazardous substances simultaneously. However, little is known about the exposure hazards in construction industry. This study was aimed at identifying the risk of exposure hazards among construction workers. Methods: The expert survey (n=29) was conducted, including construction industry health managers (n=11) and work environment monitoring experts (n=18), on exposure probability, intensity and risk of hazardous substances by construction occupations Results: The exposure hazards of 30 construction occupations were identified and summarized through a literature review and expert survey. The most prevalent hazards were in order of noise, awkward posture, heat/cold, crystalline silica, cement/concrete dust, metal fumes, and volatile organic compounds. The hazards with highest risk score(over seven points) at construction occupations were noise(formwork carpenter, concrete finisher, rebar worker, demolition worker, driller/rock blaster), hazardous rays(welder), heat/cold (earthworks, formwork carpenter, rebar worker, concrete placer, scaffolder), awkward posture(bricklayer, caulker/tile setter, rebar worker) and heavy lifting(bricklayer, rebar worker). Among construction workers, the job types with the highest risk of exposure to carcinogens, and in which occupational cancer has been reported, were in order of stonemason, concrete finisher, rock blaster, welder, insulation installer, painter, scaffolder, plant worker and earthworks in order Conclusions: Systematic research and discussion on occupational disease among construction workers and its various hazardous factors are needed to establish job exposure matrix for facilitating standard for promptly processing the workers' compensation.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.155-157
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• 2012

Recently, construction industry makes a great effort on minimizing the environmental impact. While various environmental-friendly technologies are applied to the operating phase of buildings, few equipment or machinery are partly used during the construction phase. For this reason, this study carried out a comprehensive analysis on environmental-friendly technologies for the whole construction process. In this study, appropriate environmental-friendly technologies of each construction activity were elicited to improve the environment of construction sites. Environmental-friendly technologies and construction activities were selected by professional consultation and descriptive statistics analysis, and proper environmental-friendly technologies were elicited from Cross-Impact Analysis. As a result, waste disposal and recycling technology was highly effective for demolition work while development of replacing materials was for reinforced concrete work.

• Journal of the Korean GEO-environmental Society
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• v.12 no.12
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• pp.21-30
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• 2011

The recycled soil that is proceeded from demolition concrete structures was analyzed by the methods of the physical and mechanical tests of soil and TCLP test to use the soil in low landfilling for the construction of an industrial complex. The laboratory test for diffusion of alkali ion in soil mass was analyzed by the methods of XRF and ICP. The fish toxicity test was also conducted to find an environmental influence. The recycled soil through the laboratory test satisfied the engineering property for low landfilling and the criteria of soil contamination. However, the solution which producted by 1:1 ratio of recycled soil and water contained the high pH concentration by alkali ion. The calcium hydroxide solution by CSH cement paste was estimated as the main reason why pH concentration is increased more than 9.0. The high pH concentration in recycled soils causes a toxicity to the livability of fishes. A diffusion area of pH concentration in the ground was analyzed by the Visual Modflow Ver. 2009 program based on geotechnical investigation. The high pH concentration in the recycled soils can be remained as high value due to cement paste in the long term period. Therefore, in the early stage of landfilling work, the mixing with the weathered granite soil is necessary to control the pH concentration.

• Journal of the Korea Concrete Institute
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• v.18 no.3 s.93
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• pp.431-438
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• 2006

The determination of the depth of deteriorated concrete is one of the main problems in the structural assessment of concrete structures that have been subjected to a fire. This information is particularly important in order to optimize the future operations of repair/strengthening, or in decision-making concerning a possible demolition. The purpose of this study is to propose evaluation technique of damaged depth of concrete exposed at high temperature. In order to evaluate damaged depth of core picked at member under fire, the 24 specimens have been made with variables of concrete strength(20 MPa, 40 MPa, 60 MPa) and heating exposure condition in 600 and 800 for 2 hours. Color change analysis and water absorption after heating have been measured and split tensile stress test was performed to ka the residual compressive strength against the depth of specimen. The results show that the deeper of the depth from heating face, water absorption ratio is smaller and residual stress ratio is larger and the color of heated face is changed to red color. Using this technique at damage evaluation of fired structure, We evaluate damaged depth of member under fire and determine the reasonable strengthening range.

• Journal of the Korean Recycled Construction Resources Institute
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• v.1 no.1
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• pp.42-48
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• 2013

The present study assessed the amount of $CO_2$ uptake owing to concrete carbonation through a case study for an apartment building with a principal wall system and an office building with Rahmen system under different exposed environments during use phase and recycling application. The $CO_2$ uptake assessment owing to concrete carbonation followed the procedure established by Yang et al. As input data necessary for the case study, actual surveys conducted in 2012 in Korea, which included data about the climate environments, $CO_2$ concentration, lifecycle inventory database, life expectancy of structures, and recycling activity scenario, were used. From the comparisons with the $CO_2$ emissions from concrete production, the $CO_2$ uptake during the lifetime of structures was estimated to be 5.5~5.7% and that during recycling activity after demolition was 10~12%; as a result, the amount of $CO_2$ uptake owing to concrete carbonation can be estimated to be 15.5~17% of the $CO_2$ emissions from concrete production, which roughly corresponds to 18-21% of the $CO_2$emissions from cement production as well.

• Structural Engineering and Mechanics
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• v.82 no.5
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• pp.557-569
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• 2022

The retrofit of existing structures in high seismic zones is a crucial issue in the earthquake engineering field. The interest of the research community is particularly high for the structures that do not respect current seismic codes and present structural deficiencies such as poor detailing and lack of capacity design provisions. A reinforced concrete (RC) school building is used as case study to show the influence of different knowledge levels on the seismic retrofitting cost assessment. The safety assessment of the case study building highlights deficiencies under both vertical and seismic loads. By considering all the possible knowledge levels defined by the Italian such as by the European codes in order to derive the mechanical properties of the school building constitutive materials, the retrofit operations are designed to achieve different seismic safety thresholds. The retrofit structural costs are calculated and summed up to the costs for in-situ in tests. The paper shows how for the case study building the major costs spent for a large number of in-situ tests allows to save a consistent amount of money for retrofit operations. The hypothesis of demolition and reconstruction of the building is also compared in terms of costs with all the analyzed retrofit options.

• Geomechanics and Engineering
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• v.34 no.2
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• pp.173-186
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• 2023

In order to prevent environmental pollution, initiatives to increase the sustainability of resources are supported by society. However, the performance of recycled materials does not generally match that of natural materials. This study looks into the use of geogrid to improve various types of recycled aggregates. For this purpose, five different recycled aggregates were created by recycling wastes from the construction industry. Besides, direct shear tests (DS tests) were carried out on these recycled aggregates to determine their shear strengths. Following that, a triaxial geogrid was placed in the recycled aggregates to provide reinforcement, and the DS tests were conducted on the reinforced recycled aggregates. The results of the tests were also compared to those of tests performed on natural aggregates (NA). In conclusion, it was found that the recycled aggregates have lower shear strengths than the NA. Nonetheless, when reinforced with geogrid, the shear strength of the recycled concrete aggregates (RCA) and construction and demolition wastes (CDW) exceeded that of the NA. Furthermore, the geogrid reinforcement increased the shear strength of the recycled crushed bricks (CB), though not to the level of the NA.