• Nuclear Engineering and Technology
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• 제44권3호
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• pp.331-342
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• 2012

Since the opening of the Shin-Kori #1,2 in 2005, fly ash mixed concrete has been used for NPP concrete structures under construction in Korea with the aim of preventing aging and improving durability. In this paper, the quality suitability of fly ash manufactured in Korea is assessed and the basic physical properties of fly ash mixed concrete and its durability against primary causes of aging are verified through experimental methods. Because of the internal structure filling effect from the pozzolanic reaction of fly ash and the resulting improvements in mechanical performance in such areas as strength and salt damage resistance, the durability of fly ash mixed concrete is shown to be superior. It is judged that this result can be applied in measures not only for improving the safety of NPP structures in operation in Korea but also for implementing effective structure life management should extending the life of structures be needed in the future.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 봄 학술논문 발표대회
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• pp.149-150
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• 2023

Although concrete is a material widely used in the construction industry, it is very vulnerable to cracking and has a disadvantage in that durability deteriorates when cracks occur. When cracks occur, harmful factors are introduced through the micro-cracks of the structure, reducing durability. Therefore, in this study, as part of a study to alleviate the problems of maintenance and durability deterioration due to cracks in concrete structures, the mechanical properties of self-healing mortar according to the size of the capsule made of cement material were reviewed.

• Advances in concrete construction
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• 제6권2호
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• pp.199-220
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• 2018

In this study, the effects of sulphuric acid on the mechanical performance and the durability of Engineered Cementitious Composites (ECC) specimens were investigated. The carbon fiber reinforced polymer (CFRP) and basalt fiber reinforced polymer (BFRP) fabrics were used to evaluate the performances of the confined and unconfined ECC specimens under static and cyclic loading in the acidic environment. In addition, the use of CFRP and BFRP fabrics as a rehabilitation technique was also studied for the specimens exposed to the sulphuric acid environment. The polyvinyl alcohol (PVA) fiber with a fraction of 2% was used in the research. Two different PVA-ECC concretes were produced using low lime fly ash (LCFA) and high lime fly ash (HCFA) with the fly ash-to-OPC ratio of 1.2. Unwrapped PVA-ECC specimens were also produced as a reference concrete and all concrete specimens were continuously immersed in 5% sulphuric acid solution ($H_2SO_4$). The mechanical performance and the durability of specimens were evaluated by means of the visual inspection, weight change, static and cyclic loading, and failure mode. In addition, microscopic changes of the PVA-ECC specimens due to sulphuric acid attack were also assessed using scanning electron microscopy (SEM) to understand the macroscale behavior of the specimens. Results indicated that PVA-ECC specimens produced with low lime fly ash (LCFA) showed superior performance than the specimens produced with high lime fly ash (HCFA) in the acidic environment. In addition, confinement of ECC specimens with BFRP and CFRP fabrics significantly improved compressive strength, ductility, and durability of the specimens. PVA-ECC specimens wrapped with carbon FRP fabric showed better mechanical performance and durability properties than the specimens wrapped with basalt FRP fabric. Both FRP materials can be used as a rehabilitation material in the acidic environment.

• Advances in concrete construction
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• 제6권4호
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• pp.345-362
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• 2018

In this paper, mechanical and short-term durability properties of fly ash and slag based geopolymer concretes (FAGPC-SGPC) were investigated. The alkaline solution was prepared with a mixture of sodium silicate solution ($Na_2SiO_3$) and sodium hydroxide solution (NaOH) for geopolymer concretes. Ordinary Portland Cement (OPC) concrete was also produced for comparison. Main objective of the study was to examine the usability of geopolymer concretes instead of the ordinary Portland cement concrete for structural use. In addition to this, this study was aimed to make a contribution to standardization process of the geopolymer concretes in the construction industry. For this purpose; SGPC, FAGPC and OPC specimens were exposed to sulfuric acid ($H_2SO_4$), magnesium sulfate ($MgSO_4$) and sea water (NaCl) solutions with concentrations of 5%, 5% and 3.5%, respectively. Visual inspection and weight change of the specimens were evaluated in terms of durability aspects. For the mechanical aspects; compression, splitting tensile and flexural strength tests were conducted before and after the chemical attacks to investigate the residual mechanical strengths of geopolymer concretes under chemical attacks. Results indicated that SGPC (100% slag) is stronger and durable than the FAGPC due to more stable and strong cross-linked alumina-silicate polymer structure. In addition, FAGPC specimens (100% fly ash) showed better durability resistance than the OPC specimens. However, FAGPC specimens (100% fly ash) demonstrated lower mechanical performance as compared to OPC specimens due to low reactivity of fly ash particles, low amount of calcium and more porous structure. Among the chemical environments, sulfuric acid ($H_2SO_4$) was most dangerous environment for all concrete types.

• International Journal of Concrete Structures and Materials
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• 제6권3호
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• pp.145-153
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• 2012

The aim of this study is to explore the possibility of re-cycling a waste material that is now produced in large quantities, while achieving an improvement of the mechanical properties and durability of the mortar. This study examines the mechanical properties and the durability parameters of mortars incorporating plastics bag wastes (PBW) as fine aggregate by substitution of a variable percentage of sand (10, 20, 30 and 40 %). The influence of the PBW on the, compressive and flexural strength, drying shrinkage, fire resistance, sulfuric acid attack and chloride diffusion coefficient of the different mortars, has been investigated and analyzed in comparison to the control mortar. The results showed that the use of PBW enabled to reduce by 18-23 % the compressive strength of mortars containing 10 and 20 % of waste respectively, which remains always close to the reference mortar (made without waste). The replacement of sand by PBW in mortar slows down the penetration of chloride ions, improves the behavior of mortars in acidic medium and improves the sensitivity to cracking. The results of this investigation consolidate the idea of the use of PBW in the field of construction.

• 센서학회지
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• 제31권4호
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• pp.244-248
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• 2022

Recently, several studies on the development of superhydrophobic surfaces using various nano-sized carbon-based materials have been conducted. The superhydrophobic surfaces developed using carbon soot have advantages such as low processing cost and remarkable physical and chemical properties. However, their durability is low. To address this problem, in this study, a superhydrophobic surface with high durability and a multilayer structure was fabricated using ethanol vapor treatment. Candle soot was deposited on an aluminum substrate coated with paraffin wax, and a micro-nano multilayer structure with a size of several micrometers was fabricated via ethanol vapor treatment. The fabricated superhydrophobic surface was confirmed to have a contact angle of at least 156° and high durability. Finally, it was confirmed that ethanol vapor not only changed the nanostructure of carbon but also affected the durability of the structure.

• Advances in concrete construction
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• 제11권1호
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• pp.19-32
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• 2021

In the present experimental study, the high performance hybrid fiber reinforced concrete (HPHFRC) is prepared using the Modified Andreasen and Andersen (A&A) particle packing model. Total of 16 trial mixes of HPHFRC with Indian standard sand (SS) and natural river sand (NS) are prepared to achieve the selection criteria (flow percent>150 and compressive strength>80 MPa). Based on the flow percent and compressive strength criteria, the selected mixes evaluated to study the effect of usage of natural river sand (NS) and the expensive Indian standard sand (SS) on the mechanical, durability, and microstructure property of designed HPHFRC. It has been found that the Modified A&A model is reliable to design the mix for HPHFRC with excellent mechanical, durability, and microstructure properties. In addition to that, a moderate difference in the mechanical and durability properties of NS contained HPHFRC and SS contained HPHFRC is found. Based on the obtained results of NS contained HPHFRC, it can be concluded that the use of natural river sand (NS) can be successfully adopted for the production of HPHFRC, resulted in a reduction of the production cost without compromising the excellent performance of HPHFRC.

• 한국해양공학회지
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• 제35권6호
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• pp.426-433
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• 2021

In this study, three types of synthetic fiber materials were evaluated, namely, DM20, SK78, and T147, to replace steel chains in shipbuilding and offshore fields with fiber chains as there is increasing demand for chains with lighter weights and improved usabilities. The strength and quasi-static stiffness were analyzed to select suitable yarns for the fiber chains. The durability of the yarn was evaluated by performing a 3-T (time to rupture) test as a specific tension level. The results of the experiment revealed excellent dynamic stiffness in DM20 and highest values of the windward and leeward stiffness in T147. 3-T linear design characteristic curves for a specific tension level were derived for the three types of fiber materials. The findings of this study can provide insights for improving strength and durability in fiber chain design.

• 한국농공학회논문집
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• 제62권4호
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• pp.23-31
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• 2020

Recently, meteorological disasters have been increasing by climate change, excessive rainfall, and landslide. The purpose is to develop new fabric concrete that can prevent and recover from damages because some of areas are vulnerable to meteorological disaster. Specifically, this technology can minimize time and space constraint when repairing the concrete structure and installing a formwork. The structure of fabric concrete is a mixture of fabric concrete and a high-speed hardened cement, Silica sand, wollastonite mineral fiber, fabric material and waterproof PVC fabric. In this study, the ratio of mechanical properties and durability of the fabric concrete mixture was evaluated by deriving the binder: silica sand mix ratio of the fabric concrete mixture and substituting part of the cement amount with wollastonite mineral fiber. Best binder in performance evaluation: Silica sand mix ratio is 6: 4 and the target mechanical performance and durability are the best when over 15% wollastonite binder is replaced by silicate mineral fiber.

• Advances in concrete construction
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• 제11권2호
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• pp.173-181
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• 2021

The main objective of this work is to contribute to the valorization of plastic and glass waste in the improvement of concrete properties. Waste glass after grinding was used as a partial replacement of the cement with a percentage of 15%. The plastic waste was cut and introduced as fibers with 1% by the total volume of the mixture. Mechanical and durability tests were conducted for various mixtures of concrete as compressive and flexural strengths, water absorption, ultrasonic pulse velocity, and acid attack. Also, other in-depth analyses were performed on samples of each variant such as X-ray diffraction (XRD), thermogravimetric analysis (DSC-TGA), and scanning electron microscope (SEM). The results show that the addition of glass powder or plastic fibers or a combination of both in concrete improved in the compression and flexural strengths in the long term. The highest compressive strength was obtained in the mix which combines the two wastes about 26.72% of increase compared to the control concrete. The flexural strength increased in the mixture containing the glass powder. Therefore, the mixture with two wastes exhibits better resistance to aggressive sulfuric acid attack, and incorporating glass powder improves the ultrasonic pulse velocity.