• Title/Summary/Keyword: concrete durability.

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Anti-degradation of Various Mortar Mixtures Depending on Oil Submerging Conditions (모르타르 배합비별 각종 유지류 침지에 따른 열화저항성)

  • Han, Cheon-Goo;Hwang, Chan-Woo
    • Journal of the Korea Institute of Building Construction
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    • v.17 no.3
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    • pp.219-225
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    • 2017
  • The durability factors of concrete has been researched by many researchers. Among the chemical ingression by acid, alkali, or salt, specially the ingression by sulfate has been actively studied and reported. Generally, for the oil type chemical, it is reported to cause the excessive expansion of cement mortar and further to cause the collapse, while there was no enough research on influence of oil type, relationship with microstructure of mortar, and collapse pattern. Therefore, in this research, using the various oils from general market, the degradation properties of the mortar mixtures with various mix designs were evaluated. according to the experiment, Bio diesel damaged worst and the mix design with less cement content showed the worst damage against oils.

Application of Antifungal CFB to Increase the Durability of Cement Mortar

  • Park, Jong-Myong;Park, Sung-Jin;Kim, Wha-Jung;Ghim, Sa-Youl
    • Journal of Microbiology and Biotechnology
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    • v.22 no.7
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    • pp.1015-1020
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    • 2012
  • Antifungal cement mortar or microbiological calcium carbonate precipitation on cement surface has been investigated as functional concrete research. However, these research concepts have never been fused with each other. In this study, we introduced the antifungal calcite-forming bacteria (CFB) Bacillus aryabhattai KNUC205, isolated from an urban tunnel (Daegu, South Korea). The major fungal deteriogens in urban tunnel, Cladosporium sphaerospermum KNUC253, was used as a sensitive fungal strain. B. aryabhattai KNUC205 showed $CaCO_3$ precipitation on B4 medium. Cracked cement mortar pastes were made and neutralized by modified methods. Subsequently, the mixture of B. aryabhattai KNUC205, conidiospore of C. sphaerospermum KNUC253, and B4 agar was applied to cement cracks and incubated at $18^{\circ}C$ for 16 days. B. aryabhattai KNUC205 showed fungal growth inhibition against C. sphaerospermum. Furthermore, B. aryabhattai KNUC205 showed crack remediation ability and water permeability reduction of cement mortar pastes. Taken together, these results suggest that the $CaCO_3$ precipitation and antifungal properties of B. aryabhattai KNUC205 could be used as an effective sealing or coating material that can also prevent deteriorative fungal growth. This study is the first application and evaluation research that incorporates calcite formation with antifungal capabilities of microorganisms for an environment-friendly and more effective protection of cement materials. In this research, the conception of microbial construction materials was expanded.

An Experimental Study on the Mechanical and Fire Resistance Properties of ECC Fire Resistance Panel (ECC내화패널의 역학 및 내화특성에 관한 실험적 연구)

  • Lee, Sang-Soo;Kang, Hoon
    • Journal of the Korea Institute of Building Construction
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    • v.10 no.2
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    • pp.89-96
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    • 2010
  • This study was based on an experiment that examines the manufacture and performance of fiber-reinforced cement composite panels. The conclusions were drawn after testing the mechanical properties and durability characteristics of fiber-reinforced mortar, and the mechanical properties and fire resistance of ECC fire resistant column panels. It was found that the fluidity of CEL fiber was lower than that of PVA and NY fiber. The amount of air increased slightly as the combination of fibers caused the number of fine pores to increase. It was found that the mechanical performance and deformability of high strength concrete could be improved through the confinement effect of ECC fire resistant column panels. Through continuous studies on the manufacturing and field construction methods of fire resistant column panels, a new PC method that eliminates weakness in the existing processes may be developed for skyscrapers.

The Problem of 'Bio morphism' in the works of Elizabeth Murray (엘리자베스 머레이 작품에 나타난 '바이오 형상성'에 관한 문제)

  • Park Ji-Sook
    • Journal of Science of Art and Design
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    • v.4
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    • pp.91-122
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    • 2002
  • `Bio morphism` are constituted in paintings where the artists try to embody the elementary properties of living creature as of growth and durability. They are the most appropriate concept of painting to harmonize human being with nature closely. The formative ways of them attach great importance to both unconsciousness and desire , as well as variations or dynamics, by noticing a flow of natural senses and feelings of human being. In other words, the formative ways are based on a recognition of nature as the intrinsic force of life, with the result that aesthetics of incompleteness is embodied in images. Therefore they are clearly distinguished from that of functional, geometric images. A tendency of painting at that time, in a word, 'return to figure and expression', means a conversion into organic images like the incomplete, atypical, and biomorphic forms, while denying the mechanical or geometric. Elizabeth Murray are analyzed, for these works are remarkable in the characteristics of 'Bio morphism'. Consequently the features of organic images, that is, 'the formative acceptance of natural figures, or an informality' and 'the force of free will, or an incompleteness', could obviously be revealed. It is a type that obtains a motif out of natural figures like an animal, a plant, or the concrete figures of human being. In conclusion, this thesis is focused on not only emphasizing that 'Bio morphism' were a major tendency among the various trends of postmodern painting in the 20th century, but also analysing both the painterly formation of organic images and the structure of them. In addition to these points, it is a central aim to evoke that Bio morphism should accurately be evaluated and positioned in postmodern painting. A new recognition of 'Bio morphism' is a peculiarity of the times that reflects a cultural aspect of the present, hence it should be recognized as another way to approach the postmodern painting.

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Physico-chemical and mineralogical study of ancient mortars used in Harran area (Turkey)

  • Binici, Hanifi;Akcan, Mehmet;Aksogan, Orhan;Resatoglu, Rifat
    • Advances in concrete construction
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    • v.5 no.6
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    • pp.639-658
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    • 2017
  • Very limited studies have been accomplished concerning the historical structures around Harran area. Collected mortar samples from the historic structures in the area were tested to explore their mechanical, chemical and mineralogical properties. Mortar samples from three different points of each historical structure were taken and specified in accordance with the related standards taking into consideration their mechanical, chemical and mineralogical properties. By means of SEM-EDX the presence of organic fibres and calcite, quartz, plagioclase and muscovite minerals has been examined. Additionally, by means of XRF analysis, oxide ($SiO_2$, $Al_2O_3$, and $Fe_2O_3$) percentages of mortar ingredients have been specified, also. According to the test results obtained, it was confirmed that the mortars had densities ranging between $1.51-2.10g/cm^3$, porosity values ranging between 8.89-35.38% and compressive strengths ranging between 5.02-5.90 MPa. Specimen HU, which has the highest durability and lowest water absorption and porosity, was the mortar taken from the most intact building in the mosque complex. This result is most likely due to the very little fine aggregate content of HU. In contrast, HUC mortars with a small amount of fine particles and brick contents yielded slightly lower compressive strengths. The interesting point of this study is the mineralogical analysis results and especially the presence of ettringite in these historic mortars linked to the use of pozzolanic materials. Survival of these historic structures in Harran Area through centuries of use and, also, having been subjected to many earthquakes can probably be explained by these properties of the mortars.

Analysis of Chloride Content in Aqueous Solution and Mortar using Laser Induced Breakdown Spectroscopy (LIBS를 활용한 수용액과 모르타르 내 염화물량 분석)

  • Ryu, Hwa-Sung;Park, Won-Jun
    • Journal of the Korea Institute of Building Construction
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    • v.21 no.3
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    • pp.189-194
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    • 2021
  • LIBS has been attracting attention as an analytical method capable of real-time measurement without sample preparation. In this study, a Lab. scale LIBS device was fabricated to examine the applicability and reproducibility of LIBS in the analysis of chloride contents in mortar. The existing analysis method and LIBS analysis were performed simultaneously on the mortar test specimen with the chloride content adjusted. Compared to the chloride content condition of the mortar, the XRF and Potentiometric Titration results also showed a similar trend. As a result of LIBS analysis, chlorine ions were detected at a wavelength of 837.59 nm according to the chloride content condition. In order to improve the precision in various concentration ranges, the LIBS signal amplification of about 50 times through the electric field enhancement was implemented. Through the verification of the aqueous solution-based reproducibility, a high correlation between the LIBS signal strength and the Cl concentration was confirmed, and the possibility of applying LIBS to the durability diagnosis of concrete damage by chloride was confirmed.

Structural Analysis and Safety Assessment for Constricted Bridges (협착교량의 구조해석 및 안전성 평가)

  • Jeong, Jae-Hun;Kim, Moon-Ok;Choi, Hyun-Ho;Kim, Jang-Hwan
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.26 no.6
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    • pp.33-38
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    • 2022
  • As the intense heat continues, many cases of highway pavement blow up and bridge expansion joints damages have been inspected. Especially, Expansion joint closure of bridges is an important problem that can threat the safety of the bridge structure or reduce long-term durability. This paper proposed a structural analysis method for bridges having expansion joint closure and structural analysis was performed to verify the effects according to bridge types. Analysis bridges were divided into four types: concrete and steel bridges, shallow and piled foundations. To induce the situation of abutments and bridge decks are jammed, the following loads were additionally considered; lateral flow pressure, pavement expansion by alkali-aggregate reaction, creep settlement of backfill. The structural analysis method was verified by comparing the structural analysis results with the actually measured joint gap data. In addition, behavioral analysis due to joint closure was conducted to confirm the change in safety ratio by type of superstructure as the axial force increased.

A Study of Static Behavior of FRP Bridge Deck Concerning Connection Condition (FRP바닥판의 연결조건에 따른 정적거동 분석)

  • Yong, Hwan Sun;Hwang, Yoon Koog;Kyung, Kab Su;Park, Yong Chan
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.26 no.4A
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    • pp.597-604
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    • 2006
  • Fiber Reinforced Polymer (FRP) is a relatively new material in the bridge construction. With high strength to weight ratios, excellent durability, and low life-cycle costs of FRP, FRP bridge decks can offer a low dead load, reduced maintenance, and long service life. Due to the lightweight of FRP, if existing concrete decks can be replaced with the FRP decks, the load carrying capacity of superstructure can be increased without strengthening of girders. In this study, we have conducted an experiment on 7 cases of connection conditions with steel girder by using bolts considering a rational and economical method of connection and compared with the results of FEM analysis. From the experimental result, if the bolts are strong enough to resist shear force between the FRP bridge deck and the steel girder, it will be structurally secure to use the zigzag method.

Dynamic Behavior Analysis of PSC Train Bridge Friction Bearings for Considering Next-generation High-speed Train (차세대 고속철의 증속을 고려한 PSC 철도교 마찰 교량받침의 동적 거동 해석)

  • Soon-Taek Oh;Seong-Tae Yi
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.27 no.6
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    • pp.39-46
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    • 2023
  • In this study, the dynamic behavior of friction bearings of PSC (Pre-Stressed Concrete) box train continuous bridge was numerically analyzed at 10 km/h intervals up to 600 km/h according to the increasing speed of the next-generation high-speed train. A frame model was generated targeting the 40-meter single-span and two-span continuous PSC box bridges in the Gyeongbu High-Speed Railway section. The interaction forces including the inertial mass vehicle model with 38 degrees of freedom and the irregularities of the bridge and track were considered. It was calculated the longitudinal displacement, cumulative sliding distance and displacement speed of the bridge bearings at each running speed so that compared with the dynamic behavior trend analysis of the bridge. In addition, long-term friction test standards were applied to evaluate the durability of friction plates.

Creation of regression analysis for estimation of carbon fiber reinforced polymer-steel bond strength

  • Xiaomei Sun;Xiaolei Dong;Weiling Teng;Lili Wang;Ebrahim Hassankhani
    • Steel and Composite Structures
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    • v.51 no.5
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    • pp.509-527
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    • 2024
  • Bonding carbon fiber-reinforced polymer (CFRP) laminates have been extensively employed in the restoration of steel constructions. In addition to the mechanical properties of the CFRP, the bond strength (PU) between the CFRP and steel is often important in the eventual strengthened performance. Nonetheless, the bond behavior of the CFRP-steel (CS) interface is exceedingly complicated, with multiple failure causes, giving the PU challenging to forecast, and the CFRP-enhanced steel structure is unsteady. In just this case, appropriate methods were established by hybridized Random Forests (RF) and support vector regression (SVR) approaches on assembled CS single-shear experiment data to foresee the PU of CS, in which a recently established optimization algorithm named Aquila optimizer (AO) was used to tune the RF and SVR hyperparameters. In summary, the practical novelty of the article lies in its development of a reliable and efficient method for predicting bond strength at the CS interface, which has significant implications for structural rehabilitation, design optimization, risk mitigation, cost savings, and decision support in engineering practice. Moreover, the Fourier Amplitude Sensitivity Test was performed to depict each parameter's impact on the target. The order of parameter importance was tc> Lc > EA > tA > Ec > bc > fc > fA from largest to smallest by 0.9345 > 0.8562 > 0.79354 > 0.7289 > 0.6531 > 0.5718 > 0.4307 > 0.3657. In three training, testing, and all data phases, the superiority of AO - RF with respect to AO - SVR and MARS was obvious. In the training stage, the values of R2 and VAF were slightly similar with a tiny superiority of AO - RF compared to AO - SVR with R2 equal to 0.9977 and VAF equal to 99.772, but large differences with results of MARS.