• Title/Summary/Keyword: blast-furnace-slag

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A Study on Correlation Between Cyclic Drying-Wetting Accelerated Corrosion Test and Long-term Exposure Test (건습반복 부식촉진시험 및 장기폭로시험의 상관성에 대한 연구)

  • Park, Sang-Soon
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.20 no.4
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    • pp.136-143
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    • 2016
  • There are various method for evaluating the durability life of concrete structures due to salt damage. The best way is to perform a corrosion test for a rebar embedded in concrete specimen was exposure to marine environment. However, this method has the disadvantage that it takes a long period of time. Also, accelerated corrosion test which was complemented complements the time-consuming weakness is limited to apply because it could not reveal a correlation between long-term exposure test. Accordingly, the purpose of this study is to derive a correlation coefficient between cycle drying-wetting accelerated corrosion test and long-term exposure test. Corrosion initiation time was measured in four types of concrete samples, i.e., two samples mixed with fly ash(FA) and blast furnace slag(BS), and the other two samples having two water/cement ratio(W/C = 0.6, 0.35) without admixture(OPC 60 and OPC 35). The accelerated corrosion test was carried out by two case, i.e., one is a cyclic drying-wetting method(case 1), and the other is a artificial seawater ponding test method(case 2). Whether corrosion occurs, it was measures using half-cell potential method. The results indicated that case 1 is to accelerated the corrosion of rebar about 24~36% as compared with case 2, then the corrosion of rebar embedded in concrete occurred according to the order of OPC60, FA, BS, OPC35. Correlation coefficient between accelerated corrosion test and long-term exposure test, case 1 is 4.23 to 5.42, and case 2 is 6.54 to 7.82.

Sulfate Resistance of Alkali-Activated Materials Mortar (알칼리 활성화 결합재 활용 모르타르의 황산염 침식 저항성)

  • Park, Kwang-Min;Cho, Young-Keun;Lee, Bong-Chun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.20 no.2
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    • pp.94-101
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    • 2016
  • This paper presents an investigation into the durability alkali-activated materials(AAM) mortar and paste samples manufactured using fly-ash(FA) and ground granulated blast furnace slag(GGBFS) exposed to a sulfate environment with different GGBFS replace ratios(0, 30, 50 and 100%), sodium silicate modules($Ms[SiO_2/Na_2O]$ 1.0, 1.5 and 2.0) and initial curing temperatures($23^{\circ}C$ and $70^{\circ}C$). The tests involved immersions for a period of 6 months into 10% solutions of sodium sulfate and magnesium sulfate. The evolution of compressive strength, weight, length expansion and microstructural observation such as x-ray diffraction were studied. As a results, as higher GGBFS replace ratio or Ms shown higher compressive strengths on 28 days. In case of immersed in 10% sodium sulfate solution, the samples shows increase in long-term strength. However, for samples immersed in magnesium sulfate solutions, the general observation was that the compressive strength decreased after immersion. The most drastic reduction of compressive strength and expansion of weight and length occurred when GGBFS or Ms ratios were higher. Also, the XRD analysis of samples immersed in magnesium sulfate indicated that expansion of AAM caused by gypsum($CaSO_4{\cdot}2H_2O$); the gypsum increased up to 6 months continuously.

Electrical Resistivity of ITZ According to the Type of Aggregate (골재 종류별 시멘트 경화체 계면의 전기저항 특성)

  • Kim, Ho-Jin;Bae, Je Hyun;Jung, Young-Hoon;Park, Sun-Gyu
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.9 no.3
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    • pp.268-275
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    • 2021
  • The three factors that determine the strength of concrete are the strength of cement paste, aggregate and ITZ(Interfacial Transition Zone) between aggregate and cement paste. Out of these, the strength of ITZ is the most vulnerable. ITZ is formed in 10~50㎛, the ratio of calcium hydroxide is high, and CSH appears low ratio. A high calcium hydroxide ratio causes a decrease in the bond strength of ITZ. ITZ is due to further weak area. The problem of ITZ appears as a more disadvantageous factor when it used lightweight aggregate. The previous study of ITZ properties have measured interfacial toughness, identified influencing factors ITZ, and it progressed SEM and XRD analysis on cement matrix without using coarse aggregates. also it was identified microstructure using EMPA-BSE equipment. However, in previous studies, it is difficult to understand the microstructure and mechanical properties. Therefore, in this study, a method of measuring electrical resistance using EIS(Electrochemical Impedance Spectroscopy) measuring equipment was adopted to identify the ITZ between natural aggregate and lightweight aggregate, and it was tested the change of ITZ by surface coating of lightweight aggregate with ground granulated blast furnace slag. As a result, the compressive strength of natural aggregate and lightweight aggregate appear high strength of natural aggregate with high density, surface coating lightweight aggregate appear strength higher than natural aggregate. The electrical resistivity of ITZ according to the aggregate appeared difference.

Experimental Study on the Applicability of Reactivity SiO2 Nano-Materials as Cement Composites (실리케이트계 반응성 나노소재의 시멘트 혼화재로써 적용 가능성에 대한 실험적 연구)

  • Kim, Won-Woo;Moon, Jae-Heum;Baek, Chul-Woo;Yang, Keun-Hyeok
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.9 no.4
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    • pp.529-536
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    • 2021
  • In this study, nano-silica and nano-titanium were selected to determine the possibility of applying the binder to reactive nano materials. The basic characteristics of the nano material candidate group were reviewed. and the reactivity of nano materials was reviewed through K-value. The reactivity of the nano silicate materials was measured to be high. Therefore, as a final candidate group, nano silicate materials were selected. The finally selected reactive nano material was reviewed for its usability as a construction binder. The mechanical properties and unit weight of cement paste were reviewed using silica fume and blast furnace slag and nano materials. When cement composites with nano silicate materials, it was confirmed that it was effective in improving the mechanical performance and decrease the unit weight of cement composites.

A Study on the Estimation of Optimal Unit Content of Binder for the Soil Stabilizer Using the Recycled Resource in DMM (심층혼합공법에서 순환자원을 활용한 지반안정재의 최적 단위결합재량 산정에 관한 연구)

  • Seo, Se-Gwan;Lee, Khang-Soo;Kim, You-Seong;Cho, Dae-sung
    • Journal of the Korean Geosynthetics Society
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    • v.18 no.2
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    • pp.37-44
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    • 2019
  • The compressive strength of the soil stabilizer in the deep mixing method (DMM) depends on kinds of soil, particle size distribution, and water content. Because of this, Laboratory test has to perform to estimate the unit weight of binder to confirm the satisfaction of the design strength. In this study, uniaxial compression strength was measured by mixing the soil stabilizers developed in the previous study with clay in Busan, Yeosu, and Incheon area. And the strength enhancement effect was evaluated comparing with blast furnace slag cement (BFSC). Also, the relationship between the unit content of binder and uniaxial compressive strength was investigated in order to easily calculate the unit weight of binder required to ensure the stability of the ground at the field. As the results of the analysis, the relationship between the unit content of binder and the uniaxial compressive strength are ${\gamma}_B=(108.93+0.0284q_u){\pm}35$ when W/B is 70%, and ${\gamma}_B=(122.93+0.0270q_u){\pm}40$ when W/B is 80%.

Prediction Equation for Chloride Diffusion in Concrete Containing GGBFS Based on 2-Year Cured Results (2년 양생 실험결과를 이용한 고로슬래그 미분말 콘크리트의 염화물 확산 예측식)

  • Yoon, Yong-Sik;Cho, Sung-Jun;Kwon, Seung-Jun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.23 no.2
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    • pp.1-9
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    • 2019
  • GGBFS(Ground Granulated Blast Furnace Slag), one of the representative concrete mineral admixtures, improves the long-term durability and engineering performance of concrete by latent hydraulic activity. In this study, considering 3 levels of W/B(0.37, 0.42, 0.47) and GGBFS replacement ratio(0 %, 30 %, 50 %), durability performances for chloride attack are evaluated, and equations which predict behavior of accelerated chloride diffusion are proposed. Also, the relationship between accelerated chloride diffusion coefficient and passed charge is evaluated. In target curing day, accelerated chloride diffusion tests(Tang's method, ASTM C 1202) and compressive strength(KS F 2405) are performed. In the 730 day's results of accelerated chloride diffusion coefficient, GGBFS concrete has up to 28 % of decreasing ratio compared to OPC concrete, and in those of passed charge, GGBFS concrete has up to 29 % of decreasing ratio compared to OPC concrete. Also, it is deemed that the impact of variation of W/B is less in GGBFS concrete than in OPC concrete. The equations which predict accelerated chloride diffusion coefficient and passed charge are drawn, based on the characteristics of mixture and test results. The equation which predicts passed charge shows slightly higher coefficient of determination than that which predicts accelerated chloride diffusion coefficient.

Performance of Recycled Coarse Aggregate Concrete with Nylon Fiber (나일론 섬유를 적용한 순환 굵은골재 콘크리트의 성능 평가)

  • Lee, Seung-Tae
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.23 no.2
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    • pp.28-36
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    • 2019
  • The adhered mortars in recycled aggregate may lower the performance of the concrete, such as by reducing in strength and durability, and cracking. In the present study, the effects of nylon fiber (NF) on the mechanical and durable properties of 100% ordinary portland cement (OPC) and 50% ground granulated blast furnace slag (GGBFS) concretes incorporating recycled coarse aggregate (RA) were experimentally investigated. Concrete was produced by adding 0 and $0.6kg/m^3$ of NF and then cured in water for the predetermined period. Measurements of compressive and split tensile strength, water permeable pore and total charge passed through concrete were carried out, and the corresponding test results were compared with those of concrete incorporating crushed coarse aggregate (CA). In addition, the microstructures of 28-day concretes were observed by using SEM technique. Test results revealed that the RA concrete showed lower performance than CA concrete because of the adhered mortars in RA. However, it was obvious that the addition of NF in RA concrete was much effective in enhancing the performance of the concretes due to the bridge effect from NF. In particular, the application of NF2 (19 mm) exhibited a somewhat beneficial effect compared with concrete incorporating NF1 with respect to mechanical properties, especially for RA concrete.

Properties of Low Carbon Type Hydraulic Cement Binder Using Waste Recycle Powder (무기계 재생원료를 사용한 저탄소형 수경성 시멘트 결합재의 특성)

  • Song, Hun;Shin, Hyeon-Uk;Tae, Sung-Ho
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.7 no.1
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    • pp.22-28
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    • 2019
  • Cement is a basic material for the construction industry and it requires high temperature sintering when manufacturing cement. $CO_2$ emissions from raw materials and fuels are recognized as new environmental problems and efforts are underway to reduce them. Techniques for reducing $CO_2$ in concrete are also recommended to use blended cement such as blast furnace slag or fly ash. In addition, the construction waste generated in the dismantling of concrete structures is recognized as another environmental problem. Thus, various methods are being implemented to increase the recycling rate. The purpose of this study is to utilize the inorganic raw materials generated during the dismantling of the structure as a raw material for the low carbon type cement binder. Such as, waste concrete powder, waste cement block, waste clay brick and waste textile as raw materials for low carbon type cement binder. From the research results, low carbon type cement binder was manufactured from the raw material composition of waste concrete powder, waste cement block, waste clay brick and waste textile.

Characteristics of Mine Liner According to the Replacement Ratio of Nano-Silica and Silica-Fume (나노실리카 및 실리카흄 대체율에 따른 차수재의 특성)

  • Kang, Suk-Pyo;Lee, Hee-Ra;Kang, Hye-Ju;Nam, Seong-Young;Kim, Chun-Sik
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.7 no.1
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    • pp.66-73
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    • 2019
  • Approximately 80% of the mines are vacated or abandoned mines and are mostly left without suitable environmental treatment facilities. In the area around the abandoned mine site, problems such as drainage of acidic city drainage and leakage of leachate occur, and ground subsidence caused by this can cause a safety accident due to sink hole occurrence. In this study, flow, compressive strength, water uptake, pore and hydration characteristics were investigated to investigate the basic properties of liner and cover material based on the replacement ratio of nano silica and silica fume in the existing blast - furnace slag fine powder. As a result, as the substitution ratio of nano silica and silica fume increased, the flow and compressive strength of nano silica specimens increased and the absorption rate decreased. In the case of pore characteristics, the amount of pores decreased as the substitution ratio of nano silica and silica fume increased. Especially, the capillary porosity of 10-1,000 nm diameter decreased. Ray diffraction analysis and SEM measurement showed that the peak positions of the hydration products were almost the same when compared with the 5% alternative test samples of Plain and silica fume.

Surface characteristics for thermal diffusion of FA-BFS-based geopolymer ceramics added alumina aggregate (알루미나 골재를 첨가한 FA-BFS계 지오폴리머 세라믹스의 열확산에 대한 표면 특성)

  • Kim, Jin-Ho;Park, Hyun;Kim, Kyung-Nam
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.29 no.2
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    • pp.61-70
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    • 2019
  • Geopolymer is an eco-friendly construction material that has various advantages such as reduced $CO_2$ emission, fire resistance and low thermal conductivity compared to cement. However, it has not been many studies on the thermal behavior of the surface of the geopolymer panel when flame is applied to the surface. In this study, surface characteristics of hardened geopolymer on flame exposure was investigated to observe its characteristics as heat-resistant architectural materials. External structure changes and crack due to the heat shock were not observed during the exposure on flame. According to the residue of calcite and halo pattern of aluminosilicate gel, decarboxylation and dehydration were extremely limited to the surface and, therefore, it is thought that durability of hardened geopolymer was sustained. Gehlenite and calcium silicate portion was inversely proportional to quartz and calcite and significantly directly proportional to BFS replacement ratio. Microstructure changes due to the thermal shock caused decarboxylation and dehydration of crystallization and it was developed the pore and new crystalline phase like calcium silicate and gehlenite. It is thought that those crystalline phase worked as a densification and strengthening mechanism on geopolymer panel surface.