• Title/Summary/Keyword: concrete durability.

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Evaluation of Durability Characteristics of High Performance Shotcrete Using Fly Ash (폐석탄회를 이용한 고성능 숏크리트의 내구특성 평가)

  • Park, Cheol-Woo;Lee, Hyeon-Gi;Kang, Tae-Sung
    • Journal of the Korea Concrete Institute
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    • v.22 no.3
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    • pp.305-311
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    • 2010
  • The industrial by-product market has increased at a geometric rate worldwide with the rapid economic growth. At present time, conventional disposal methods of industrial by-products in Korea including landfill, incineration and storage already have reached their limits. In this study, the industrial by-products such as fly ash and silicafume were used as mineral admixtures, which are commonly added to concrete mix to inhance the economic efficiency, long-term strength and durability of concrete, to determine the optimized mix proportion of high performance shotcrete. Through the series of tests (compressive strength test, accelerated chloride ion penetration test, measurement of chloride diffusion coefficient). The results of the study showed that the proposed mix proportions satisfied the requirements of domestic as well as international guidelines for shotcrete, with a higher durability than the existing shotcrete.

A Study on the Watertightness Improvement of Cementitious Material for Durability Improvement of Concrete (콘크리트 내구성 향상을 위한 시멘트 재료의 수밀성 개선에 관한 연구)

  • Kang, Hyun-Ju;Song, Myong-Shin;Jeong, Eui-Dam
    • Journal of the Korean Society of Hazard Mitigation
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    • v.10 no.5
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    • pp.17-25
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    • 2010
  • We studied on the watertightness improvement of cementitious material for durability enhancement of concrete. For improvement of watertightness of OPC and OPC with fly ash, we used various materials with watertightness properties to OPC and OPC with fly ash. The performance of watertightness improvement of cementitious materials closely related to formation of CSH by pozzolanic reaction and to reducing of size of contact angle in cement pore by using organic fatty acid. And volume of CSH formation at early hydration have an influence of watertightness improvement and reduction of long-term water absorption rate. In using of fly ash, improvement of workability by using the spherical fly ash caused to densify on the structures of cement material and CSH formation by pozzolanic reaction and cement using fly ash also caused watertightness improvement of cementitious materials. For improvement of concrete durability by watertightness, cementitious materials need using watertightness materials and at using fly ash, also it have to the effect of improvement of watertightness of cementitious materials by pozzolanic reaction.

Durability of Polymers for Cement Modifier in Autoclave Cure (오토클래이브양생에 의한 시멘트 혼화용 폴리머의 내구성)

  • Joo, Myung-Ki;Lee, Youn-Su
    • Journal of the Korea Concrete Institute
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    • v.15 no.6
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    • pp.888-893
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    • 2003
  • The purpose of this study is to make clear the durability of the polymer films formed in the autoclaved polymer-modified mortars and concretes. The polymer films prepared with polymer dispersions such as a styrene-butadiene rubber (SBR) latex, a poly (ethylene-vinyl acetate)(EVA) emulsion and a polyacrylic ester (PAE) emulsion for polymeric admixtures are exposed to autoclaving at 18$0^{\circ}C$ in temperature and 1.01 MPa in vapor pressure, and subjected to tensile test and infrared spectroscopy. The durability of the polymer films is evaluated from the application of autoclaving to the polymer films under saturated Ca(OH)$_2$ solution immersion causes no degradation for SBR films and a significant degradation due to the saponification of the polymers for EVA and PAE films. Accordingly, in the application of autoclaving to polymer-modified mortars and concretes, it is suggested that SBR-modified mortars and concretes are hardly degraded but EVA- and PAE-modified mortars and concretes are markedly degraded by the saponification of the polymers.

Performance of FRP confined and unconfined geopolymer concrete exposed to sulfate attacks

  • Alzeebaree, Radhwan;Gulsan, Mehmet Eren;Nis, Anil;Mohammedameen, Alaa;Cevik, Abdulkadir
    • Steel and Composite Structures
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    • v.29 no.2
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    • pp.201-218
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    • 2018
  • In this study, the effects of magnesium sulfate on the mechanical performance and the durability of confined and unconfined geopolymer concrete (GPC) specimens were investigated. The carbon and basalt fiber reinforced polymer (FRP) fabrics with 1-layer and 3-layers were used to evaluate the performances of the specimens under static and cyclic loading in the ambient and magnesium sulfate environments. In addition, the use of FRP materials as a rehabilitation technique was also studied. For the geopolymerization process of GPC specimens, the alkaline activator has selected a mixture of sodium silicate solution ($Na_2SiO_3$) and sodium hydroxide solution (NaOH) with a ratio ($Na_2SiO_3/NaOH$) of 2.5. In addition to GPC specimens, an ordinary concrete (NC) specimens were also produced as a reference specimens and some of the GPC and NC specimens were immersed in 5% magnesium sulfate solutions. The mechanical performance and the durability of the specimens were evaluated by visual appearance, weight change, static and cyclic loading, and failure modes of the specimens under magnesium sulfate and ambient environments. In addition, the microscopic changes of the specimens due to sulfate attack were also assessed by scanning electron microscopy (SEM) to understand the macroscale behavior of the specimens. Results indicated that geopolymer specimens produced with nano-silica and fly ash showed superior performance than the NC specimens in the sulfate environment. In addition, confined specimens with FRP fabrics significantly improved the compressive strength, ductility and durability resistance of the specimens and the improvement was found higher with the increased number of FRP layers. Specimens wrapped with carbon FRP fabrics showed better mechanical performance and durability properties than the specimens wrapped with basalt FRP fabrics. Both FRP materials can be used as a rehabilitation material in the sulfate environment.

Carbonation Analysis of Bridge Structures in Urban Area Based on the Results of the Field Test (현장실험결과를 활용한 국내 도심지 교량구조물의 탄산화 해석)

  • Kim, Hun-Kyom;Kim, Sung-Bo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.14 no.4
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    • pp.111-118
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    • 2010
  • Reinforced steel corrosion due to concrete carbonation is one of main factors on the durability of RC structure. The carbonation velocity have an effect on carbon dioxide density, concrete quality and structural shape. Specially, these problems have increased in urban area. This study investigates the carbonation status of the bridges and quantifies the effect of carbonation based on various domestic field data. The failure probability of durability is evaluated on the basis of reliability concept. According to experimental results of the carbonation depth, the carbonation depth increased with structural age and carbonation velocity decreased with high strength of concrete. In most cases, the failure probability of durability by carbonation was more than 10%. Also, The results requires the minimum cover thickness of 70-80mm for target safety index(${\beta}$=1.3) proposed by Korean concrete specification.

A Long-term Durability Prediction for RC Structures Exposed to Carbonation Using Probabilistic Approach (확률론적 기법을 이용한 탄산화 RC 구조물의 내구성 예측)

  • Jung, Hyun-Jun;Kim, Gyu-Seon
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.14 no.5
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    • pp.119-127
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    • 2010
  • This paper provides a new approach for durability prediction of reinforced concrete structures exposed to carbonation. In this method, the prediction can be updated successively by a Bayes' theorem when additional data are available. The stochastic properties of model parameters are explicitly taken into account in the model. To simplify the procedure of the model, the probability of the durability limit is determined based on the samples obtained from the Latin Hypercube Sampling(LHS) technique. The new method may be very useful in design of important concrete structures and help to predict the remaining service life of existing concrete structures which have been monitored. For using the new method, in which the prior distribution is developed to represent the uncertainties of the carbonation velocity using data of concrete structures(3700 specimens) in Korea and the likelihood function is used to monitor in-situ data. The posterior distribution is obtained by combining a prior distribution and a likelihood function. Efficiency of the LHS technique for simulation was confirmed through a comparison between the LHS and the Monte Calro Simulation(MCS) technique.

Effects of sulphuric acid on mechanical and durability properties of ECC confined by FRP fabrics

  • Gulsan, Mehmet Eren;Mohammedameen, Alaa;Sahmaran, Mustafa;Nis, Anil;Alzeebaree, Radhwan;Cevik, Abdulkadir
    • Advances in concrete construction
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    • v.6 no.2
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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.

A Study on the Durability Evaluation Criteria for the Vertical Extension Remodeling of Apartment (수직 중축형 리모델링 안전진단 내구성 평가기준 합리화에 관한 연구)

  • Yoon, Sang-Chun;Shin, Dong-Cheol
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.24 no.6
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    • pp.197-205
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    • 2020
  • In 2014, The Housing Act amended to allows vertical extension and increases the units of housing (or total floor area) to site. Currently, the feasibility of performing vertical extension is evaluated based on safety diagnosis provisions and manuals with 1st investigation stage on slope, uneven settlement, load-bearing capacity, and durability. However, a need for more reasonable evaluation criteria for the investigation is still required because there had not been any other case study on the diagnosis for the vertical extension, and the engineering basis on evaluation criteria were not suggested. Accordingly, this study is intended to suggest feasible evaluation criteria on the carbonation, chloride ion contents, corrosion of reinforcements, crack and surface deterioration of concrete for durability assessment by codes and standards of domestic and foreign countries. The results of this study are expected to be beneficial for establishing more reasonable durability evaluation criteria, and in turn, more reliable assessment protocol for vertical extension.

Fundamental Properties of High Performance Concrete using Crushed Stone Fines (쇄석분을 사용한 고성능콘크리트의 기초 특성)

  • 이승한;정용욱;박정준
    • Proceedings of the Korea Concrete Institute Conference
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    • 1999.10a
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    • pp.263-266
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    • 1999
  • This study aims to make high performance concrete for normal strength using crushed stone fines to control high strength of the high performance concrete. According to the experimental results, when crushed stone fines are increased every 10%, 15% of compressive strength is decreased, and 5% of drying shrinkage is increased, compared to normal high performance concrete. Also, high performance concrete has been evaluated to have good durability factor more than 100% in the 480cycle of freezing and thawing test, without regard to using AE and crushed stone fines.

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Properties of Reinforced Concrete Used for Disposal Container of Low-and Intermediate-level Radioactive Wastes (중.저준위 방사성 폐기물 처분용기용 보강 콘크리트의 특성)

  • 황의환;황선태;홍원표;조헌영
    • Journal of the Korean Ceramic Society
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    • v.25 no.5
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    • pp.455-464
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    • 1988
  • Concrete used for radwaste container should have excellent properties such as mechanical strength, water-tightness, durability, etc. In order to improve such properties of ordinary portland cement concrete, superplasticizer, steel fiber, and/or epoxy resin were added to ordinary portland cement concrete respectively. Various concrete specimens were prepared and the physical properties of each concrete specimen were tested. From the experimental results, the properties of steel fiber and epoxy resin reinforced concrete were proved to be better qualified than others for low-and intermediate-level radwaste container.

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