• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.4
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• pp.287-294
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• 2019

GGBFS(Ground Granulated Blast Furnace Slag) has been widely used in concrete for its excellent resistance chloride and chemical attack, however cracks due to hydration heat and dry shrinkage are reported. In many International Standards, GGBFS with low fineness of 3,000 grade is classified for wide commercialization and crack control. In this paper, the mechanical and durability performance of concrete were investigated through two mix proportions; One (BS) has 50% of w/b(water to binder) ratio and 60% replacement ratio with low-fineness GGBFS, and the other (TS) has 50% of w/b and 60% replacement ratio with 4000 grade and FA (Fly Ash). The strength difference between TS and BS concrete was not great from 3 day to 91 day of age, and BS showed excellent performance for chloride diffusion and carbonation resistance. Two mixtures also indicate a high durability index (more than 90.0) for freezing-thawing since they contain sufficient air content. Through improvement of strength in low fineness GGBFS concrete at early age, mass concrete with low hydration heat and high durability can be manufactured.

• Resources Recycling
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• v.19 no.6
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• pp.36-42
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• 2010

Researches on resources recycling in the field of construction have made an extensive progress such as recycled aggregate of waste concrete and recycling of asphalt. On the other hand, there are almost never researches on pavement method with used waste frying oil. In South Korea, 0.2 million ton used waste frying oil is discharged every year. It is guessed that about 0.1 million ton used waste frying oil can be collected. If used waste frying oil is recycled, it is expected that disuse cost will be reduced and water pollution of rivers will be prevented. Therefore, the purpose of the study was to evaluate on mechanical features (strength, water resistance, chemical resistance, abrasion resistance, freezing and thawing resistance and permeable coefficient) whether dense graded permeable concrete mixing silica sand with flexible alkyd resin manufactured by making ester reaction with collected used waste frying oil to make alkyd resin could be applied to road pavement for non-roadway. The results of the study were as follows. In flexural strength, it had 1.6 times as much as road design standard 4.5MPa. In water resistance, chemistry resistance and freezing and thawing resistance, they had lack of strength in early age. As age went by, they didn't have large changes. And curing temperature had phenomenon of increase in strength at rather low temperature than high temperature by glass transition temperature of resin. Therefore, considering workability, strength and durability when it was applied to road pavement, it was reasonable that the mixing ratio of flexible alkyd resin was 10~15% in comparison with silica sand weight.

• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.2
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• pp.101-108
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• 2019

This study is analysis of the utilization as a concrete fine aggregate on CGS, a by-product of Integrated coal gasification combined cycle(IGCC). That is, in KS F 2527 "Concrete aggregate," properties of 1~12times to CGS were evaluated, focusing on quality items corresponding to natural aggregate sand(NS) and melted slag aggregate sand(MS). As a result, the distribution of grain shape, safety and expansion were all satisfied with KS standards by physical properties, but the quality was unstable at 7~12times of water absorption ratio and absolute dry density. The particle size distribution was unstable due to asymmetry distribution of coarse particles, and particles were too thick for 7~12times. The passing ratio of 0.08mm sieve was also out of the KS standard at part factor of 7~12times, but chloride content, clay contents, coal and lignite were all satisfactory. Meanwhile, chemical composition was satisfactory except for $SO_3$ in 1~6times, and content and amount of harmful substances were all within the specified value except for F in 7~12times. As a result of SEM analysis, the surface quality and porosity were 7~12times more than 1~6times, and it was the quality was degraded. Therefore, it is necessary to reduce the quality deviation by using separate measures in order to utilize it as concrete aggregate in the future, and if it is premixed with fine quality aggregate, it will contribute positively to solve aggregate supply shortage and utilize circulation resources.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.324-330
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• 2018

In accordance with the amendment of the Industrial Safety and Health Act of 2007, Korea completely prohibited the import, distribution and manufacture of asbestos like Europe and Japan. Accordingly, the current problem of asbestos is the safe maintenance and disposal of asbestos construction material, the disposal of asbestos, and the final disposal of asbestos building materials. In the past, Korea used 100,000 tons of asbestos every year, and the building materials using it exceeded 1 million tons per year. These asbestos building materials continued to be used until 2006, and the Ministry predicted that these materials would continue to be maintained until 2044. When the permeable hardening agent is applied to the asbestos building material installed in the pre-pretreatment step for the harmless treatment of the asbestos waste and the dismantling is carried out, the scattering of the asbestos is suppressed in the disassembling step, detoxification treatment conditions can be improved. Therefore, permeable hardeners should be stably penetrated into asbestos building materials. In this study, it is suggested that pre - pretreatment methods for the harmlessization of waste asbestos building materials with medium density level can be presented. In order to efficiently perform pre - treatment for chemical harmlessness in the future, the mixing ratio of permeable hardener and middle water Optimization is the most important factor.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.252-258
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• 2018

A larger energy consumption and concentration of population induced green house gas glowing and heat island effect in the urban space. Roof green system was a effect method to reduce green house gas and heat concentration in the city. Therefore, construction of this system was increasing. Most of lightweight soil used in roof green system was perlite, but this caused dust and skin disease. So it needed to develop another new lightweight soli for roof green system. Meanwhile, a thermoelectric power plant generated bottom ash as a by-product. According to previous research, bottom ash could be used for artificial lightweight soil with 60 wt% of mixing rate. But this study was proceed to develop a artificial lightweight soil using bottom ash with higher mixing rate by 65 wt% and different organic ingredients. First, physical and chemical properties of bottom ash was investigated. Then test according to landscaping design standard was proceeded for various artificial lightweight soil mix types using bottom ash, bark, compost and coco peat. As a result, the artificial lightweight soil with 65% of bottom ash, 30% of bark and 5% of compost was suitable for low and middle range of soil standard.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.357-364
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• 2018

Fly ash is a material used as a concrete admixture. When fly ash is used for concrete manufacturing, it is expected to improve the performance such as reduction of cement usage and increase of chemical resistance. However, fly ash have some problems such as unburned carbon content and amorphous film on the surface of fly ash particles. When concrete is manufactured using fly ash containing a large amount of unburned carbon, there is a problem that the slump is lowered due to adsorption of AE agent. In addition, the amorphous film on the surface of the particles prevents the reactive substances from leaching out of the fly ash. Therefore, a method of surface treatment of fly ash using plasma has been studied to remove such unburned carbon and amorphous films. However, plasma has the problem that $O_3$ is generated when $O_2$ is used as an active gas. $O_3$ is a harmful substance and adversely affects the health of the experimenter. In this study, the surface of fly ash was treatment by arc discharge. Experimental results show that the unburned carbon is removed when the surface of fly ash is treatment by arc discharge and the amorphous film was broken and the reactivity was improved. Therefore, it is considered that arc discharge can treatment the surface of fly ash and improve the quality of fly ash.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.3
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• pp.204-210
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• 2022

Cement is pointed out as the main cause of carbon dioxide emission in the construction industry. Many researchs are underway to use blast furnace slag, an industrial by-product, as a substitute for cement to reduce carbon dioxide emitted during the manufacturing the cement. When blast furnace slag is used as a substitute for cement, it has advantages such as long-term strength and chemical resistance improvement. However, blast furnace slag has a problem that makes initial strength low. This is due to the impermeable film on the surface created during the production of blast furnace slag. The created film is known to be destroyed in an alkaline environment, and based on this, previous studies have suggested a solution using various alkali activators. But, alkali activator is dangerous product since it is a strong alkaline material. And it has the disadvantage in price competitiveness. In this study, an experiment was conducted to improve the initial hydration reactivity of the blast furnace slag to secure the initial strength of the mortar substituted with the blast furnace slag and to check whether the carbonation resistance was increased. As a result of the experiment, it was confirmed that the mortar using alkaline water showed higher strength than the mortar using tap water, and there were more hydration products generated inside. In addition, it was confirmed that the mortar using alkaline water as a compounding water had high carbonation resistance.

• Journal of the Korean Recycled Construction Resources Institute
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• v.10 no.4
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• pp.482-488
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• 2022

In this study, the durability of ultra rapid hardening mortar for sewage pipe was evaluated by type of mortar binder. As a result of analyzing the internal structure for each type of mortar, it was confirmed that Al₂(OH)₃ was generated in the internal structure of the CAC-based mortar, and its corrosion resistance was superior to that of other types of mortar. As a result of the compressive strength test, OPC had the tsmallest strength, followed by CAC100 > CAC100P > CAC80. This trend was similar to the previous study results. Chloride ion penetration resistance and freeze-thaw test showed similar trends. That is, CAC and C12A7 were better than OPC, and CSA was worse than OPC. This is mostly beacuse of cracks caused by expansion of CSA-based mortar. CAC100P mix showed the best chemical resistance. It is thought that this is because the alumina gel formed inside the mortar and the polymer combine to make the internal structure more dense.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.2
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• pp.153-160
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• 2023

In this study, nano-sized C-S-H crystals were synthesized using the liquid phase reaction method and their properties were investigated. The synthesized C-S-H crystals were added to the cement composite in suspension form to determine their effect on the hydration properties of the cement. The amount of chemical admixture was varied to obtain nano-sized C-S-H crystals with optimal agglomerated morphology, and SEM photographs were analyzed. A cleaning process was added to remove harmful substances other than the synthesiz ed C-S-H crystals. It was found that the concentration of harmful substances was reduced in the case of C-S-H crystals subjected to the cleaning process. The synthesized C-S-H suspensions were prepared with and without the cleaning process, and cement composites were prepared with the cement weight content as the main variable. The effect of C-S-H crystals on the initial hydration properties of the cement was confirmed by microhydration heat analysis. In addition, mortar specimens were prepared to measure the compressive strength over time. The test results showed that the nano-sized C-S-H crystals act as nucleation sites in the cement paste to promote the early hydration of the cement and increase the early compressive strength.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.2
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• pp.112-119
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• 2023

In this study, the variations in CO₂ uptake according to the type and amount of alkali-based activator (Ca(OH)₂, CSA) of geopolymer paste were evaluated. As the amount of activator added to the geopolymer paste increased, the fluidity of the paste is decreased and the compressive strength increased. According to the type of activator, it was confirmed that the addition of Ca(OH)₂ had a greater effect on improving the compressive strength than CSA. As a result of changes in chemical properties according to carbonation curing, the amount of C-S-H and C-A-S-H gels produced before carbonation increased as the amount of activator increased, and amount of CaCO₃ produced after carbonation increased. The reactivity of the blast furnace slag and zeolite increased due to the addition of the activator, and the reactivity tended to increase as the amount of addition increased. As a result of CO₂ uptake, 10.3 wt% when Ca(OH)₂ 10 % was added and 8.77 wt% when CSA 10 % was added was confirmed. It increased by 421 % and 388 % respectively, compared to the case where no activator was added.