• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.3
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• pp.77-84
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• 2012

It is known that some components of wood obstruct the hydration of cement when wood is mixed with cement. In order to examine the effect of pretreatment of wood chips in hot water, this study conducted the experiments for the setting and compressive strength of mortar by sieving pine wood chips with a 2.4mm sieve, dipping them in waters of different temperatures, and then using them as a part of the fine aggregate. For the experiments, water-cement ratio of the mortar was 0.50 and the amount of the fine aggregate substituted by wood chips was set at 0%, 2%, 4%, 6%, 8%, and 10% of the mass of the fine aggregate. As a result of the test, it was found out that when wood chips were used to substitute fine aggregate for the production of mortar, more usage of wood chips postponed setting more, and the treatment of wood chips with water improved the problem of the delay in setting time. Especially, the final setting time of the mortar which used 2~6% of wood chips treated in $100^{\circ}C$ water for 30 minutes was almost the same as the final setting time of the mortar which used no wood chips. Also, the compressive strength of the mortar which used the wood chips treated with water was compared to that of the mortar which used the wood chips not treated with water. The result showed that the strength improved for age of 7 days and 28 days, while there was little change in strength for age of 3 days.

• Geotechnical Engineering
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• v.14 no.1
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• pp.109-126
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• 1998

The use of fly ash as a contaminant barrier material was studied. Mixing ratio of fly ash to bentonite to meet the requirements for landfill liners was determined. The hydraulic behavior exhibited by the fly ash-bentonite liner and the effects of CaO were investigated through hydraulic conductivity tests under various conditions and microscopic analyses including XRD, SEM, helium porosimetry, and image analysis. The hydraulic conductivity of compacted fly ash decreased with the addition of bentonite, which was due mainly to the expanding of bentonite and partly to the filling of voids by chemical reaction products among constituents of the artificial liner. Because of insufficient CaO content, and rich in content but low-reactive $SiO_2$ contained in the fly ashes used, pozzolanic reaction and resulting effects in the artificial liner were not significant. The reactions among constituting materials and their resulting effects on hydraulic conductivity were controlled not by the apparent amounts of each constituent, but by reaction activities of the materials in the artificial liner.

• Journal of the Korean Recycled Construction Resources Institute
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• v.3 no.2
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• pp.132-139
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• 2015

In this study, the different unit cement content by the ratio of water absorption and water-cement ratio are applied to examine the properties of the concrete used the aggregate recycled by the crushing treatment. According to the experimental results, in the mix of low strength and high water-cement ratio, both of the compressive strength is almost equal in the concrete using the recycled aggregate by the crushing treatment and the concrete using broken stones. It means that the recycled aggregate has the low effect of the amount of bonded mortar. But, in the mix of high strength and low water-cement ratio, the concrete using the recycled aggregate by the crushing treatment has 40% less of the compressive strength than that using broken stones by the effect of the amount of bonded mortar. On the other hand, after 8 weeks, the dry shrinkage of the recycled aggregate with 7% of the ratio of water absorption doubles that of the broken stones with 1% ($-350{\times}10^{-6}$), in other words $-700{\times}10^{-6}$. Thus, the dry shrinkage should be prior to any other conditions in recycling waste concrete for the aggregate for concrete. When the recycled aggregate with 3% of the ratio of water absorption is used, the compressive strength of the rich mix concrete ($450kg/m^3$ of the unit cement content) is equivalent to that of the concrete using broken stones, while in using the recycled aggregate with 7% of the ratio of water absorption, the rich mix concrete has 7% lower compressive strength than the concrete using broken stones. But, the compressive strength of the ordinary mix concrete ($350kg/m^3$ of the unit cement content) is far lower than that using broken stones.

• Journal of the Korea Institute of Building Construction
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• v.18 no.1
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• pp.25-31
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• 2018

In this study, the Controlled Low Strength Material (CLSM) was investigated to utilize the bottom ash and fly ash generated in the Circulating Fluidized Bed Combustor (CFBC). It was confirmed that the CFBC fly ash (CFBC-F) and CFBC bottom ash (CFBC-B) had an irregular particle shape through SEM measurement. According to the results of the hazard analysis, it was also confirmed that they were environmentally safe. In the case of mixing with CFBC-F, the unit quantity was increased. Regarding the rate of change of length, shrinkage in the range of -0.05~0.50% occurred in the air dry curing condition and expansion in the range of 0.1~0.6% in the sealed curing condition. Compressive strength was increased in the sealed curing condition compared to the air dry curing condition because there was enough moisture for hydration reaction in the long term. Therefore, the results of this study are likely be used as basic research data of mine filler materials.

• Korean Journal of Construction Engineering and Management
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• v.16 no.6
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• pp.41-52
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• 2015

The number of military facilities has been rapidly increased due to growing requirement of modernization and military welfare. However, adequate maintenance has not implemented to these facilities. As a result, they are deteriorated quickly and require performance enhancement treatments. There are two ways of performance enhancement, reconstruction and remodeling. Despite the research result that remodeling within the standard remodeling range is more economical, remodeling of military facilities is not considered equivalent to reconstruction as an option of performance improvement. Therefore, derived from the relationship between performance change during life cycle of building and range of remodeling needs, this study tries to propose Remodeling Process Model(RPM) which uses a method to choose remodeling in a Specific Point of Time(SPT) when remodeling is considered more economical than reconstruction. In addition, this study suggests practical service life and functionality evaluation standard together which require to realize the RPM. This RPM make it possible to avoid the cases that facilities which do not have any problem on structural reliability but have low level of functionality miss appropriate remodeling timing and inevitably choose reconstruction as a performance improvement option. It also present the possibility of simple reconstruction / remodeling decision-making for facility managers who administrate building having various type, compilation and elapsed time. Consequently, this process model focusing on remodeling more may contribute to reduce resource waste caused by reconstruction.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.1
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• pp.93-101
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• 2010

When doing underground excavation works for the purpose of constructing large underground structures for a building in the limited space in downtown area, the stability of the adjacent ground must be top priority, and to accomplish this, it is essential to review the retaining wall construction carefully. H-Pile, which has been mainly used as a stress-carrying material in temporary earth-retaining structures, is most likely to be abandoned after completion of the works for the basement exterior wall in relation to contiguous bored piles, so it will result in a waste of material. To improve this situation, Basement Composite Wall where H-Pile and basement wall are compounded, has been developed. This wall is being used most frequently in many local construction sites. In this study, five specimens are made in order to evaluate the shear resistance of the basement composite wall and tested. Test parameter is the composition ratio and wall thickness according to shear connectors. Test result shows that the shear strength is improved when the composite ratio is increased but the magnitude is not much. A formula, which considers the contribution of concrete, web of H-pile as well as flange' effect in calculation of shear strength of composite basement wall, is suggested and used to calculation of the strength of specimens. It is found that there is a good co-relation between test result and the calculated one by the formula.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.3
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• pp.236-245
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• 2021

It is very important for structure designer to understand the service life variation since a wide range of service life is evaluated with changing exposure conditions and design parameters. Recently, for zero-carbon, waste plastic has been used for fuel for clinker production and this yields increase in chloride content in cement. This study is for evaluation of changing service life in the concrete with increasing initial chloride content due to usage of plastic-SRF(Solid Refuse Fuel) considering various exposure conditions and design parameters. For this, 4 levels of initial chloride content were assumed, and the service life was assessed using LIFE 365 program considering various environmental conditions including 3 levels of surface chloride content. As for analysis parameters, critical/initial chloride content, blast furnace slag powder replacement ratio, W/B(Water to Binder) ratio, cover depth, and unit mass for binder are adopted. Service life decreases with increasing initial chloride content and a significant reduction of service life is not evaluated permitting up to 1,000ppm of initial chloride content. With increasing slag replacement ratio, a longer service life can be secured since blast furnace slag powder has the effect of reducing the diffusion of external chloride ions and fixing the free chloride. It is thought that increasing initial chloride content up to European standard is helpful for enhancing sustainability and reducing carbon emission. Though the reduction in service life due to an increase in the initial chloride content is not significant in slag-concrete with low surface chloride content, careful consideration for mixing design should be paid for the exposure environment with high surface chloride content.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.3
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• pp.295-302
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• 2021

Surface modification of recycled plastic film-based aggregates is demonstrated to enhance the interaction between aggregates and cement paste. It is shown that the oxygen(O₂) atmospheric pressure plasma(APP) treatment leads to a drastic increase in hydrophilicity. In case of the plasma treatment at 100W of RF power, 15/4sccm of O₂/Ar flow rate and 30sec of discharging time, the water contact angle on the aggregates surface decreased from 104.5° to 44.0°. In addition, the contact angle of surface modified aggregates kept in air increased with time elapse. Improvement of hydrophilicity can be explained by the formation of new hydrophilic oxygen functional groups which is identified as C-OH, C-O-C, C=O, -COOH by X-ray photoelectron spectroscopy(XPS) analysis and Fourier-transform infrared spectroscopy(FT-IR). Therefore, it can be concluded that the plasma treatment process is an effective method to improve adhesion of the recycled plastic film-based aggregates and cement paste.

• Journal of the Korean Recycled Construction Resources Institute
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• v.9 no.4
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• pp.478-482
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• 2021

In this paper, methods for manufacturing shielding concrete by recycling steelmaking slag discarded as industrial waste and measuring the shielding effectiveness of the shielding concrete were studied. By comparing the result of shielding effectiveness measurement of this concrete block with shielding effectiveness measurement of the structure constructed with this concrete, the measurement system for measuring shielding effectiveness of the concrete block was verified. The size of the concrete stru ctu re is 2.9 × 2.9 × 3.4m and the concrete block is 0.3 × 0.3 × 0.2m. The frequ ency band u sed for mesu rement is 600MHz - 2GHz, the types of concrete u sed to measu re the shielding effectiveness are general concrete and concrete containing electric arc furnace oxidizing slag. In the case of the concrete structure, reinforcing rebars are installed at intervals of 15cm for stru ctu ral safety, as the frequ ency increase, the electromagnetic wave properties of rebars gradu ally decreased, there was a slight difference in the measurement results. In conclusion, the measurement result of shielding effectiveness of the concrete block is similar to the result of the concrete structure. It is thought that it can be sufficiently utilized for electromagnetic wave engineering design, and the concrete shielding effectiveness measurement system using standard specimens was verified.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.4
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• pp.387-394
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• 2020

In this research, a physical property test of CLSM, which can safely and effectively utilize a great number of industrial byproducts and waste types, was used to review the applicability of GBFS, FNS, and FGB, as well as their field applicabilities as cavity fillers, and the following conclusions have been reached. first, For CLSM utilizing GBFS, FNS, and FGB, it was revealed that a proper mixing of over 30% of GBFS and FNS or within 5% of FGB is effective in improving the fluidity for field application. second, It was revealed that GF15B5 can suppress bleeding at a similar level as the base, whereas GF30B5 can do so at about 0.17% compared to the base. It was also verified that GF15, GF30, and GF45 can suppress bleeding at about 0.2%, 0.26%, and 0.3%, respectively, compared to the base. third, Both GF15B5 and GF30B5 exceeded 0.4MPa in 7day strength tests to satisfy the field application and, also, the rates of increase of their initial strengths were found to be 323% and 233% higher than the base, respectively. Meanwhile, the 7day strength test of GF, which utilizes GBFS and FNS, also reached over 0.2MPa for field application, and it was revealed that GF15, GF30, and GF45 show 160%, 237%, and 185% higher strength increase rates, respectively, compared to the base.