• 산업기술연구
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• 제25권B호
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• pp.3-10
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• 2005

Since in 1970, the length of concrete pavements(JCP, JRCP and CRCP) are growing rapidly at both of main highways and local roads. Many of them are deteriorated and old enough to be repaired or replaced. The pavement is more important than the other infrastructures and it is very difficult to go around or block the traffic during the rehabilitation. The very-early strength latex-modified concrete(VES-LMC)may offer the advantages of high-early-strength, higher flexural strength, higher bond strength, and improved durability. The VES-LMC could be used at a kind of fast track ofr early opening to the traffic after 3 hours of concrete placement. The installation of VES-LMC overlay at Jung-Boo highway was successfully done from April 28 to 29, 2005. The traffic was closed at 07:00 PM and opened to traffic at 08:30 AM. The compressive and flexural strength of VES-MC were more than 28MPa, 6.2MPa after 4 hours, respectively.

• Structural Engineering and Mechanics
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• 제69권1호
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• pp.77-93
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• 2019

Although much research has been carried out using recycled aggregates sourced from normal strength concrete, most of the buildings to be demolished are constructed with low strength concrete. Therefore, the properties of the concrete incorporating recycled aggregates, sourced from the waste of structural elements cast with low strength concrete, were investigated in this study. Four different concrete mixtures were designed incorporating natural and recycled aggregates with and without fly ash. The results of the mechanical and durability tests of the concrete mixtures are presented. Additionally, full-scale one-way reinforced concrete slabs were cast, using these concrete mixtures, and subjected to bending test. The feasibility of using conventional reinforced concrete theory for the slabs made with structural concrete incorporating recycled aggregates was investigated.

• Computers and Concrete
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• 제22권5호
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• pp.449-459
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• 2018

Concrete is one of the most widely used construction materials in the world. Producing economical and durable concrete is possible by employing pozzolanic materials. The aim of this study is to underline the possibility of the utilization of natural zeolite in producing concrete and investigate its effects basically on the strength and durability of concrete. In the production of concrete mixes, Portland cement was replaced by the natural zeolite at ratios of 0%, 10%, 15%, and 20% by weight. Concretes were produced with total binder contents of $300kg/m^3$ and $400kg/m^3$, but with a constant water to cement ratio of 0.60. In addition to compressive and flexural strength measurements, freeze-thaw and high temperature resistance measurements, rapid chloride permeability, and capillary water absorption tests were performed on the concrete mixes. Compared to the rest mixes, concrete mixes containing 10% zeolite yielded in with the highest compressive and flexural strengths. The rapid chloride permeability and the capillary measurements were decreased as the natural zeolite replacement was increased. Freeze-thaw resistance also improved significantly as the replacement ratio of zeolite was increased. Under the effect of elevated temperature, natural zeolite incorporated concretes with lower binder content yielded higher compressive strength. However, the compressive strengths of concretes with higher binder content after elevated temperature effect were found to be lower than the reference concrete.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.471-474
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• 2005

Reliability-based durability model was developed to consider the uncertainty of analysis variables in durability model for harbor concrete structures. The durability analysis program based on Finite Element Method (FEM) was modified adopting the reliability concept to estimate the probability of durability failure. Water-cement ratio in the durability analysis is the most important factor influencing chloride diffusion coefficient, evaporable water, etc. The probability distribution of water-cement ratio was calculated converting standard deviations of compressive strength in Concrete Standard Code to those of water-cement ratio. Based on the Monte Carlo Simulation, the probabilities of penetration depth and durability failure were calculated.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표논문집(II)
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• pp.392-397
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• 1998

In this paper, the properties of cement mortar used recycled aggregate are analyzed and compared with river and crushed sand mortar. Recycled aggregates are made by crushing wasted concrete had various compressive strength, and test items are the properties of fresh mortar, hardened mortar and durability. According to the experimental results, flow, unitweight, strength and durability of cement mortar used recycled aggregates decrease compared with those of river and crushed sand mortar.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회논문집(I)
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• pp.455-460
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• 2000

Fly ash can be used as cement replacement material and can also produce the durable concrete. According to the results, the compressive strength of concrete containing fly ash is slightly lower than that of normal concrete at early ages, however, the long-term compressive strength is significantly higher beyond 90 days, and it increases the durability of concrete as well.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.605-608
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• 2006

This paper presents experimental results for durability performance of GFRP composite exposed to various environmental conditions. Specimens were conditioned for 7 environmental cases and immerged up to 150 days. A total of 720 specimens were prepared and tested for tensile strength for each immersion time. The results indicate that the tensile strength of the conditioned specimens was significantly reduced, regardless of the environmental factors considered, due to the degradation of GFRP.

• Structural Engineering and Mechanics
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• 제64권2호
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• pp.243-257
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• 2017

Investigating the properties and durability of high-strength concrete exposed to sulfuric acid attack for the purpose of its application in structures exposed to this acid is of outmost importance. In this research, the resistance and durability of high-strength concrete containing macro-polymeric or steel fibers together with the pozzolans of silica fume or nano-silica against sulfuric acid attack are explored. To accomplish this goal, in total, 108 high-strength concrete specimens were made with 9 different mix designs containing macro-polymeric and steel fibers at the volume fractions of 0.5, 0.75, and 1.0%, as well as the pozzolans of silica fume and nano-silica with the replacement levels of 10 and 2%, respectively. After placing the specimens inside a 5% sulfuric acid solution in the periods of 7, 21, and 63 days of immersion, the effect of adding the fibers and pozzolans on the compressive properties, ultrasonic pulse velocity (UPV), and weight loss of high-strength concrete was investigated and the respective results were compared with those of the reference specimens. The obtained results suggest the dependency of the resistance and durability loss of high-strength concrete against sulfuric acid attack to the properties of fibers as well as their fraction in concrete volume. Moreover, compared with using nano-silica, using silica fume in the fibrous concrete mix leads to more durable specimens against sulfuric acid attack. Finally, an optimum solution for the design parameters where the crushing load of high-strength fibrous concrete is maximized was found using response surface method (RSM).

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2005년도 춘계 학술기술논문발표대회 논문집
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• pp.165-169
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• 2005

The fire damage of building wouid effect on the safety of structure. When the reinforced concrete structure is heated by high temperature due to the fire, the structural resisting-force will be decreased. In a way, it is a requirement to use high strength concrete for high rise building. Particularly, fire resistance properties of high-strength concrete is more important than normal strength concretes. The fire outbreak of a high strength concrete by sudden temperature rise is a main problem, and causes crack by thermal stress, loading to the deterioration of the durability. In this study, normal and high strength mortar were exposed to a high temperature environment. And than fundamental data for the character change of concrete heated highly were presented by measuring compressive strength of concrete with polypropylene and vinylon fiber, before and after heating. As the results, it is proven that high strength mortar with polypropylene and vinylon fiber for prevents deterioration of durability by fiber.

• 한국지반환경공학회 논문집
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• 제17권12호
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• pp.35-43
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• 2016

시공기술의 발전과 더불어 댐 제방 건설과 환경문제가 크게 대두되고 있는 실정이다. 최근 여러 국가에서 댐 제방 건설시 골재, 시공성, 기초지반에 대한 요구가 상대적으로 높지 않은 CSG(Cemented Sand and Gravel)재료를 활발히 연구, 적용하고 있다. CSG 재료는 시공현장 하상골재, 현장에서 발생하는 암버럭 등을 인위적으로 입도조정하지 않고 최대골재 치수만을 선별하여 소량의 시멘트와 혼합하여 강도증가 및 급속시공이 가능하다. CSG 재료는 인위적인 석산개발 등에 의한 환경파괴를 최소화함으로써 환경부하저감 및 공사비 등의 측면에서 비교적 경제적이며 친환경적이다. CSG 재료의 외부환경은 일반콘크리트가 접하는 수화열환경과는 달리 건습반복, 동결융해 등의 환경에 노출되게 된다. 그러므로 댐 제방구조물의 중요성을 감안하여 CSG 재료의 내구성에 대한 연구가 필요하다. 본 연구는 CSG 재료의 내구성에 대하여 고찰하고자 현장채취 CSG 코어재료에 대하여 동결융해 시험을 실시하였다. 시험결과, CSG 재료의 내구성 지수는 시멘트함량 $0.4{\sim}0.6kN/m^3$의 경우 30~40, $0.8{\sim}1.0kN/m^3$의 경우 40 이상으로 나타났다. 일축압축강도는 $0.4{\sim}0.6kN/m^3$에서 동결융해 전의 30~50%, $0.8~1.0kN/m^3$에서 동결융해 전의 40~70%로 감소하는 것으로 나타났다. 결과적으로 시멘트함량 $0.8kN/m^3$이상의 경우 강도 및 내구성 측면에서 비교적 타당한 것으로 판단된다.