• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2016년도 춘계 학술논문 발표대회
• /
• pp.122-123
• /
• 2016

Sulfate anion which cause concrete degradation is affected on marine structures. There are two of control method concrete degradation which is arisen by sulfate anion. Cementitious materials prevent permeation of sulfate anion and water-binder ratio increase to improve watertightness. But, those methods are passive. So, this study is developing new materials which prevent actively concrete degradation on sulfate anion.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1998년도 가을 학술발표대회 논문집(III)
• /
• pp.946-951
• /
• 1998

In order to calculate the thermal stresses of massive concrete structures in non-steady state conditions the thermal properties of the materials have to be well known. Structural materials such as concrete, rock and soil are heterogeneous, damp and porous so that measurements of their thermal properties by conventional methods would result in large errors. In this study, thermal conductivity was measured by the device, QTM-D3 which is usually used in Japan. Variables are chosen as age, water content, temperature, aggregate content, S/A ratio and type of cementitious materials. Finally a model for thermal conductivity was proposed.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
• /
• pp.359-362
• /
• 2005

Self diagnosis monitoring system is defined as concrete structural carbon and glass hybrid fiber materials, in response to the change in external disturbance and environments, toward structural safety and serviceability as well as the extension of structural service life. In this study, carbon and glass hybrid fiber materials were investigated fundamentally for the applicability of self diagnosis in smart concrete structural system as embedded functions of sensors.

• Journal of the Korean Wood Science and Technology
• /
• 제44권1호
• /
• pp.57-66
• /
• 2016

이 연구에서는 환경부하가 적은 산림훼손지 생태복원재료의 개발을 목적으로, 콘크리트와 국내산 침엽수 4종, 국내산 활엽수 3종의 제재라미나를 복합적층하여, 휨 크리프 성능에 미치는 수종의 밀도의 영향을 조사하였다. 목재-콘크리트 복합적층재의 휨 크리프곡선은 수종에 관계없이 시간에 따라 크리프곡선의 우측상변이 현저히 증가하는 형태를 나타내었고, 하중부하 후 약 30분 - 1시간 이후에서는 목재 및 목질재료와 같이 거의 직선적인 거동을 나타내는 것이 확인되었다. 목재-콘크리트 복합적층재의 초기변형은 수종의 밀도의 증가에 비례하여 변형이 감소하였고, 이 값은 콘크리트의 0.9 - 1.2배의 값을 나타내었다. 목재-콘크리트 복합적층재의 크리프변형은 콘크리트의 0.4 - 0.8배의 낮은 값을 나타내어 복합적층에 의한 콘크리트의 크리프변형의 현저한 감소가 확인되었다. 목재-콘크리트 복합적층재의 상대 크리프는 8.2 - 17.0%의 범위로 복합적층에 의해 콘크리트의 그것보다 0.3 - 0.7배의 매우 낮은 값을 나타내는 것이 확인되었다. 이 결과는 목재와 콘크리트의 복합적층에 의해 기존 콘크리트재료의 크리프변형을 감소시킨 산림훼손지 생태복원재료로 응용가능성을 나타낸다.

• Journal of the Korean Wood Science and Technology
• /
• 제44권1호
• /
• pp.48-56
• /
• 2016

이 연구에서는 환경부하가 적은 산림훼손지 생태복원용 단위격자틀을 개발하기 위하여 콘크리트와 국내산 침엽수 4종과 활엽수 3종을 각각 복합적층한 7종류의 목재-콘크리트 복합적층재를 제작하였고, 정적 휨 강도성능에 미치는 수종의 밀도의 영향을 조사하였다. 목재-콘크리트 복합적층재의 휨 탄성계수는 전반적으로 수종의 밀도에 비례하여 증가하였고, 대부분 콘크리트에 비해 높은 휨 탄성계수를 나타내어 복합적층에 의한 밀도감소와 탄성계수향상의 효과가 나타났다. 휨 탄성계수 실측치는 각 라미나의 탄성계수로부터 등가단면법을 이용하여 계산한 예측치보다 약간 낮은 값을 나타내었고, 그 차이는 10% 미만인 것이 확인되었다. 목재-콘크리트 복합적층재의 휨 비례한도 응력은 콘크리트보다 1.2-1.6배의 높은 값을 나타내었다. 목재-콘크리트 복합적층재의 휨 강도는 전반적으로 수종의 밀도에 비례하여 증가하였고, 복합적층에 의해 콘크리트의 그것보다 현저한 강도향상을 나타내어 목재-콘크리트 복합적층재는 환경부하가 적으면서 내구성을 지닌 생태복원용 재료로 응용가능 할 것으로 판단된다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
• /
• pp.781-786
• /
• 2001

The Salt attack is one of the primary factors that cause the deterioration of durability in steel reinforced concrete structure. And to depreciate the deterioration from the Salt attack in concrete structure, pozzolanic materials are used widely in recent years. In this study, experiments about the resistance of chloride infiltration of concrete according to the replacement rations of Activated Hwangtoh and various pozzolanic materials(silica fume, fly ash, blast furnace slag and non Activated/Activated Hwangtoh) are performed and the results of this study were shown as follows; 1) As the replacement ratios of Activated Hwangtoh were getting higher, the strength of concrete was increased and in case of various pozzolanic materials, strength of Activated Hwangtoh in specimen was better than that of fly ash, blast furnace slag and non Activated Hwangtoh. 2) As the replacement ratios of Activated Hwangtoh were getting higher, the resistance of chloride infiltration of concrete was increased and in case of various pozzolanic materials, silica fume is better than any other pozzolanic materials and Activated Hwangtoh was better than that of fly ash, blast furnace slag and non Activated Hwangtoh.

• International Journal of Concrete Structures and Materials
• /
• 제9권4호
• /
• pp.487-498
• /
• 2015

A proper initial curing is a very simple and inexpensive alternative to improve concrete cover quality and accordingly extend the service life of reinforced concrete structures exposed to aggressive species. A current study investigates the effect of wet curing duration on chloride penetration in plain and blended cement concretes which subjected to tidal exposure condition in south of Iran for 5 years. The results show that wet curing extension preserves concrete against high rate of chloride penetration at early ages and decreases the difference between initial and long-term diffusion coefficients due to improvement of concrete cover quality. But, as the length of exposure period to marine environment increased the effects of initial wet curing became less pronounced. Furthermore, a relationship is developed between wet curing time and diffusion coefficient at early ages and the effect of curing length on time-to-corrosion initiation of concrete is addressed.

• Structural Engineering and Mechanics
• /
• 제86권4호
• /
• pp.431-441
• /
• 2023

The aim of this paper is to present a new sustainable ternary and quaternary binder by partially replacing ordinary Portland cement (OPC) with different percentages of supplementary cementitious materials. The motivation is to reduce our dependency on OPC to reduce CO₂ emission and carbon foot print. As the main substitute for the OPC, siliceous fly ash was used. Moreover, silica fume and nanosilica were also used. During examinations the main mechanical parameters of concrete composites, i.e., compressive strength (f_cm) and splitting tensile strength (f_ctm) were assed. The microstructure of these materials was also analysed. It was found that the concrete incorporating pozzolanic materials is characterized by a well-developed structure and has high values of mechanical parameters. The quaternary concrete containing: 80% OPC, 5% FA, 10% SF, and 5% nS have shown the best results in terms of good strength parameters as well as the most favourable microstructure, whereas the worst mechanical parameters with microstructure containing microcracks at phase interfaces were characterized by concrete with more content of FA additive in the concrete mix, i.e., 15%. Nevertheless, all concretes made on quaternary binders had better parameters than the reference one. It can be stated that sustainable concrete incorporating pozzolanic materials could be good substitute of ordinary concretes.

• International Journal of Railway
• /
• 제7권3호
• /
• pp.85-89
• /
• 2014

The use of pozzolanic materials in concrete mixtures can enhance the mechanical properties and durability of concrete. By reactions with pozzolanic materials and calcium hydroxide in cement matrix, calcium-silicate-hydrate (C-S-H) increases and calcium hydroxide decreases in cement matrix of concrete. Consequently, the volume of solid materials increases. The pozzolanic particles also fill spaces between clinker grains, thereby resulting in a denser cement matrix and interfacial transition zone between cement matrix and aggregates; this lowers the permeability and increases the compressive strength of concrete. Moreover, the total contents of alkali in concrete are reduced by replacing cements with pozzolanic materials; this prevents cracks due to alkali-aggregate reaction (AAR). In this study, nanosilica is incorporated in cement pastes. The differences of microstructural compositions between the hydrated cements with and without nanosilica are examined using nanoindentation, XRDA and $^{29}Si$ MAS NMR. The results can be used for a basic research to enhance durability of concrete slab tracks and concrete railway sleepers.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
• /
• pp.545-550
• /
• 2002

Concrete is one of the essential structural materials in the construction. But, concrete consists of many materials and is affected by many factors such as properties of materials, site environmental situations, and skill of constructor. Therefore, concrete mixes depend on experiences of experts. However, it is more and more difficult to determine concrete mixes design by empirical means because more ingredients like mineral and chemical admixtures are included. Artificial Neural Networks(ANN) are a mimic models of human brain to solve a complex nonlinear problem. They are powerful pattern recognizers and classifiers, also their computing abilities have been proven in the fields of prediction, estimation and pattern recognition. Here, among them, the back propagation network and radial basis function network are used. Compositions of high-performance concrete mixes are eight components(water, cement, fine aggregate, coarse aggregate, fly ash, silica fume, superplasticizer and air-entrainer). Compressive strength and slump are measured. The results show that neural networks are proper tools to minimize the uncertainties of the design of concrete mixtures.