• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.676-681
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• 2000

This paper covers durability and field application of marine concrete which have been enhanced the resistance against deterioration in seawater. Fly ash concrete is applied to make the concrete with good durability. It is well known fly ash in concrete has a good performance preventing fro a sulphate attack and a steel corrosion. Several durability tests were performed to find characteristics of marine concrete which is proposed in this paper comparing with normal concrete. Field application was executed to compare results with laboratory test and to give a reliability to engineers. The project was supported by Ministry of Marine Affairs and Fisheries for two years.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제15권4호
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• pp.2469-2475
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• 2014

In 1990s, with the increase of domestic building renovation but also increase the amount of anchor. The 45-degree cone failure theory has been used in concrete anchor bolts design, but the CCD (concrete capacity design) method was adopted as a new design method since 2000. However, the method has some problems because it is based on the experimental results of pre-installed concrete anchor bolts. In this study, the objective is to investigate the effects of anchor edge distance, anchor interval and concrete strength on pullout characteristics of post-installed concrete set anchor embedded in plain concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 1998년도 봄 학술발표회논문집(II)
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• pp.695-702
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• 1998

The purpose of this study is to investigate the mechanical properties of precast concrete cured by accelerated curing methods such as, steam curing method and warm water curing method varing maximum temperature of curing along to the period of curing. Some specimens are cured by accelerated curing method(warm water curing method) and then deposited in the storehouse. The others are deposited in the storehouse directly. All of these are cured until being tested to compare these two group's mechanical characteristics for each period 3days, 7days, 28days. The goal of this comparison is to estimate the efficiency of accelerated curing method in the case of precast concrete stocked in the field or warehouse for a long term and to make guide line for factory manager to make a economical products of concrete of a good quality. We can conclude some guide lines 1) It is not efficient to cure concrete with accelerated method at higher than 80℃. 2) The continuing of curing period more than 36hr makes damage to concrete in using accelerated curing method. 3) The strength revelation of concrete cured by accelerated curing methods, added rice husk ash more delayed than OPC concrete done but the strength of maximum value is higher than OPC concrete. 4) It is not efficient to use accelerated curing method in the case of storing the products for more than 7days in the aspect of mechanical properties.

• Journal of the Korea Concrete Institute
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• 제11권4호
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• pp.107-116
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• 1999

The damage in concrete structures generally starts with microcracking and thus it is important to find and explore these microcracks in concrete in order to ensure appropriate safety and serviceability. The purpose of the present study is to identify the damage characteristics of concrete structures due to cracking by employing the acoustic emission techniques. A comprehensive experimental study has been done. The cracking damage under tensile and flexural loadings have been identified and the bond damage between steel and concrete have been also characterized. It is seen that the amplitudes and energy level of Acoustic Emission(AE) events are found to be relatively small for bond cracking damages and large for tensile cracking damages. The characteristic equations of the AE events for various cracking damages have been proposed based on the present test data. The internal microcracks are progressively developed ahead of a visible actual crack and the present study clearly exhibits these damage mechanism for various types of cracking in concrete. The present study provides useful data which can be used to identify the various types of cracking damages in concrete structures. This will allow efficient maintenance of concrete structures through monitoring of internal cracking based on acoustic emission.

• Advances in concrete construction
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• 제8권2호
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• pp.119-126
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• 2019

This paper reports an experimental investigation conducted to evaluate the durability performance of concrete mixtures prepared utilizing blends of Type I Portland cement (OPC) and natural pozzolans (NPs) obtained from three different sources in Saudi Arabia. The control concrete mixture containing OPC alone as the binder and three concrete mixtures incorporating NPs were prepared keeping water/binder ratio of 0.4 (by weight), binder content of $370kg/m^3$, and fine/total aggregate ratio of 0.38 (by weight) invariant. The compressive strength and durability properties that included depth of water penetration, depth of carbonation, chloride diffusion coefficient, and resistance to reinforcement corrosion and sulfate attack were determined. Results of this study indicate that at all ages, the compressive strength of NP-admixed concrete mixtures was slightly less than that of the concrete containing OPC alone. However, the concrete mixtures containing NP exhibited lower depth of water penetration and chloride diffusion coefficient and more resistance to reinforcement corrosion and sulfate attack as compared to OPC. NP-admixed concrete showed relatively more depth of carbonation than OPC when subjected to accelerated carbonation. The results of this investigation indicates the viability of utilizing of Saudi natural pozzolans for improving the durability characteristics of concrete subjected to chloride and sulfate exposures.

• Advances in concrete construction
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• 제7권2호
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• pp.75-85
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• 2019

The present study is focused on the mechanical and durability properties of ternary blended cement concrete mix of different grades 30 MPa, 50 MPa and 70 MPa. Three mineral admixtures (fly ash, silica fume and lime sludge) were used as a partial replacement of cement in the preparation of blended concrete mix. The durability of ternary blended cement concrete mix was studied by exposing it to acids HCl and $H_2SO_4$ at 5% concentration. Acid mass loss factors (AMLF), acid strength loss factor (ASLF) and acid durability factor (ADF) were determined, and the results were compared with the control mix. Chloride ions penetration was investigated by conducting rapid chlorination penetration test and accelerated corrosion penetration test on control mix and ternary blended cement concrete. From the results, it was evident that the usage of these mineral admixtures is having a beneficiary role on the strength as well as durability properties. The results inferred that the utilization of these materials as a partial replacement of cement have significantly enhanced the compressive strength of blended concrete mix in 30 MPa, 50 MPa and 70 MPa by 42.95%, 32.48% and 22.79%. The blended concrete mix shown greater resistance to acid attack compared to control mix concrete. Chloride ion ingress of the blended cement concrete mix was low compared to control mix implying the beneficiary role of mineral admixtures.

• Computers and Concrete
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• 제12권5호
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• pp.717-737
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• 2013

In this study, experiment and numerical analysis were conducted to identify the heat transfer characteristics and behavior of high-strength concrete upon a fire. The numerical analysis was employed to forecast the characteristics and properties of the high-strength concrete upon a fire, which can not be accomplished through a fire test due to the specific conditions and restrictions associated with the test. The result of the numerical analysis was compared with that of the test to verify the reliability of the analysis. In the numerical analysis of the heat transfer characteristics and behavior of 80 and 100 MPa high-strength concrete upon a fire, the commercial software of ABAQUS(V.6.8) was used. It was observed from the experiment that the contraction of the concrete with fiber-cocktail was mitigated by 25~55 % compared with that without fiber-cocktail because the fiber controlled the heat transfer of the concrete and thus improved the fire-resistance performance of the column.

• Proceedings of the Korean Institute of Building Construction Conference
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• 한국건축시공학회 2007년도 춘계학술논문 발표대회
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• pp.67-70
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• 2007

As construction industry is requiring competitive power and technique in national construction market with rapid fluctuation of construction environment and development, requirements upgrading performance in construction materials are increasing. But, national lightweight aggregate and lightweight concrete's inappropriateness when produced are also increasing. And there are not international standard of aggregates in using these construction materials because standards and characteristics of aggregate in each countries are different. Therefore, in this study, lightweight aggregate acquired due to wide range of use is tested and mixed for concrete to gain practicality and set the authorized manual in international. Also, basic data will be proposed to set a standard for concrete by analyzing lightweight aggregate characteristics. When lightweight aggregate absorptivity is high, concrete shows low strength and when it's density is low, concrete shows low weight of unit volume. Furthermore, compressive strength of lightweight aggregate is steep in first and longtime material age is tendency to cause low strength increasing rate.

• Advances in concrete construction
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• 제5권4호
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• pp.313-330
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• 2017

Geopolymer is a sustainable concrete, replaces traditional cement concrete using alternative sustainable construction materials as binders and alkaline solution as alkaline activator. This paper presents the strength characteristics of geopolymer concrete (GPC) developed with fly ash and GGBS as binders, combined Sodium silicate ($Na_2SiO_3$) and Sodium Hydroxide (NaOH) solution as alkaline activators. The parameters considered in this research work are proportions of fly ash and GGBS (70-30 and 50-50), curing conditions (Outdoor curing and oven curing at $600^{\circ}C$ for 24 hours), two grades of concrete (GPC20 and GPC50). The mechanical properties such as compressive strength, split tensile strength and flexural strength along with durability characteristics were determined. For studying the durability characteristics of geopolymer concrete 5% $H_2SO_4$ solutions was used and the specimens were immersed up to an exposure period of 56 days. The main parameters considered in this study were Acid Mass Loss Factor (AMLF), Acid Strength Loss Factor (ASLF) and products of degradation. The results conclude that GPC with sufficient strength can be developed even under Outdoor curing using fly ash and GGBS combination i.e., without the need for any heat curing.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• 제20권3호
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• pp.297-306
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• 2022

The acoustic emission (AE) is proposed as a feasible method for the real-time monitoring of the structural damage evolution in concrete materials that are typically used in the storage of nuclear wastes. However, the characteristics of AE signals emitted from concrete structures subjected to various environmental conditions are poorly identified. Therefore, this study examines the AE characteristics of the concrete structures during uniaxial compression, where the storage temperature and immersion conditions of the concrete specimens varied from 15℃ to 75℃ and from completely dry to water-immersion, respectively. Compared with the dry specimens, the water-immersed specimens exhibited significantly reduced uniaxial compressive strengths by approximately 26%, total AE energy by approximately 90%, and max RA value by approximately 70%. As the treatment temperature increased, the strength and AE parameters, such as AE count, AE energy, and RA value, of the dry specimens increased; however, the temperature effect was only minimal for the immersed specimens. This study suggests that the AE technique can capture the mechanical damage evolution of concrete materials, but their AE characteristics can vary with respect to the storage conditions.