보고서 정보
주관연구기관 |
한국건설생활환경시험연구원 |
보고서유형 | 연차보고서 |
발행국가 | 대한민국 |
언어 |
한국어
|
발행년월 | 2012-02 |
과제시작연도 |
2010 |
주관부처 |
국토교통부 Ministry of Land, Infrastructure, and Transport |
등록번호 |
TRKO201600003746 |
과제고유번호 |
1615001909 |
사업명 |
건설기술혁신사업 |
DB 구축일자 |
2016-07-16
|
키워드 |
자기치유.표면보호재.콘크리트.반응성 실리콘.광반응성 폴리머.수반응성 폴리머.균열센서.Self healing.surface protecting materials.concrete.reactive silicone.photo reactive polymer.humidify reactive polymer.crack sensor.
|
초록
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- 대다수의 콘크리트 표면에 존재하는 균열은 열화요인(염소이온, 이산화탄소, 물)의 침투에 대한 빠른 침투 통로가 되어 내구성능을 저하시킴.
- 균열이 발생한 콘크리트의 수명을 연장하기 위한 중요한 사항은 열화 요인으로 인한 위험성을 재고하는 것
- 균열폭이 작은 콘크리트를 보호하기 위해 표면도장 공법이 사용되고 있음
- 표면도장공법은 균열내부를 충진 할 수 없으며, 균열이 성장하면 그 움직임을 추정하기 어려운 결점이 있음에도 불구하고 균열폭이 미세한 범주에서 간단히 균열보수 효과를 얻을 수 있다는 편리성 때문에 현
- 대다수의 콘크리트 표면에 존재하는 균열은 열화요인(염소이온, 이산화탄소, 물)의 침투에 대한 빠른 침투 통로가 되어 내구성능을 저하시킴.
- 균열이 발생한 콘크리트의 수명을 연장하기 위한 중요한 사항은 열화 요인으로 인한 위험성을 재고하는 것
- 균열폭이 작은 콘크리트를 보호하기 위해 표면도장 공법이 사용되고 있음
- 표면도장공법은 균열내부를 충진 할 수 없으며, 균열이 성장하면 그 움직임을 추정하기 어려운 결점이 있음에도 불구하고 균열폭이 미세한 범주에서 간단히 균열보수 효과를 얻을 수 있다는 편리성 때문에 현장에서는 보편적으로 사용하고 있는 방법임
- 콘크리트에 균열이 발생했을 때 표면도장이 파손되어 균열이 발생되더라도 균열 폭이 0.3mm까지는 자기 치유할 수 있는 self healing "Surface protection system for concrete"를 구축함으로써 콘크리트 수명 연장을 통하여 유지관리 LCC비용을 줄여 유지관리 비용을 최소화 하고자함
- 본 연구에서 개발한 제품이 콘크리트에 균열이 발생하여 표면도장재가 파손되더라도 0.3mm까지 치유할 수 있는 코팅제를 개발하였다. 개발된 제품을 자기치유 능력, 내투수성, 염소이온침투저항성, 중성화저항성, 습기투과도, 부착강도 등을 평가하여 개발 목표치 이상의 성능을 확인하였음
Abstract
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Concrete is the most widely used man-made building materials on the planet.
Concrete structures have been built since the discovery of Portland Cement(PC) in the midst of the nineteenth century. The reaction of PC with water results in hydration products, which glue the reacting cement particles
Concrete is the most widely used man-made building materials on the planet.
Concrete structures have been built since the discovery of Portland Cement(PC) in the midst of the nineteenth century. The reaction of PC with water results in hydration products, which glue the reacting cement particles together to form a hardened cement paste. When cement and water are mixed with sand, the resulting product is called mortar.If the mixture also contains coarse aggregate, the resulting products is called concrete. It is a quasi-brittle material, strong in compression but relatively week in tension. Concrete elements loaded in bending or in tension easily crack. For this reason reinforcement is installed Passive reinforcement is activated as soon as the concrete cracks. The formation of crack is considered a inherent feature of the reinforced concrete. Cracks that may promote deterioration of the concrete itself or may penetrate into the concrete, finally causing rebar corrosion.
With the aim to reduce the concrete's susceptibility to ingress of hannful substances the con-crete surface can be foreseen with a dense coating.
Any damage of the coating will jeopardize its protective function and may result in premature failure of the coating. These coatings are then, by definition, exposed to all external actions a structure is exposed to. If it were possible to develop a self healing coating, the use of such coatings will reduce the maintenance costs and enhance the service life of concrete structures. the use of such coatings will reduce the maintenance costs and enhance the service life of concrete structures.
The quality of concrete structures largely depends on the quality and available thickness of the concrete cover. From observations in the practice it is known that the quality of the concrete cover exhibits a big scatter. The main reasons for this big scatter are carelessness and execution failures. This project focuses on enhancement of the protective function of the concrete cover by the application of self healing coating on the concrete surface.
The use of coatings and/or sprays on concrete surfaces is not new. Well known is the hydrophobic treatment of the concrete surfaces in order to reduce the permeability of the concrete. When placed on the concrete surface, the coating is exposed to all external actions, both environmental loads (temperature, drying and wetting, sun light, frost) and mechanical loads. Deterioration of the bond between concrete and coating is another cause of premature failure of coatings. It would be a big step forward if we could develop a coating with self healing properties, both for autonomous repair of the coating itself and of the bond between coating and substrate, i.e. concrete.
In this project four sub-topics are defined concentrating on:
1. The properties of the coating - development towards a self healing coating
2. Interface coating - substrate (concrete)
3. Substrate (concrete): required properties versus available properties
4. Full scale testing
The objective of the nroject is to develop test ann]y and evaluate self healing protective coatings for reducing the maintenance costs and enhancement of the durability of concrete structures.
RELEVANCE
Sustainability: Concrete structures suffer from various damage phenomena which shorten their life and require increased maintenance and usage of materials. By using self healing coatings more durable and sustainable structures can be obtained.
Efficiency: More durable concrete structure will mitigate the pressure on the environment in terms of CO2 emissions and use of scare raw materials.
Decreasing Life Cycle Costs: Repair and maintenance costs of infrastructural work make out about 40% to 50% of the money spent in the building industry. The use of innovative materials concepts in the project may result in an increase in initial construction cost. However, because of lower maintenance costs and longer service life the overall life cycles costs are expected to be lower.
Greening of the building industrv: The developed technologies are expected to reduce signi-ficantly the need for new concrete by extending the service life of surface concrete struc-tures. Production of concrete is known to be one of the contributors to global air pollution.
Preservation of aesthetic value: The protective coating will help preserving the initial aesthe-tic performance of concrete surfaces, thus reducing the costs for aesthetic maintenance.
Project description
Self-healing concrete
The principle feature of self healing materials is that they start to heal after (small) damage has occurred. This damage can be in de form a crack. In concrete cracking is a common phenomenon due to the relatively low tensile strength. High tensile stresses can result from external loads, imposed deformations (due to temperature gradients, confined shrinkage, differential settlement), plastic shrinkage, plastic settlement, expansive reactions (e.g. due to reinforcement corrosion, alkali silica reaction, sulphate attack). Many of these cracks start at the surface of the concrete and then penetrate deeper into the concrete. The durability of concrete is impaired by these cracks, since they provide an easy path for transportation of liquids and gasses that potentially contain harmful substances. If microcracks grow and reach the reinforcement, not only the concrete itself may be attacked (direct degradation). Also the reinforcement will be corroded when it is exposed to water and oxygen, and possibly carbon dioxide and chlorides (indirect degradation). Microcracks are therefore precursors to structural failure. Self-healing of microcracks will lead to structures with longer lifetime and less maintenance. In fact, concrete in itself possesses some self-healing properties, due to the continuing hydration of clinker minerals and precipitation of CaCO3. To rely completely on the self healing capacity of concrete,however,is not considered justified.
(Self healing) Coatings on concrete
Dense, more ore less impermeable coatings applied on the surface of porous concrete will prevent the ingress of hazardous substances into the concrete. Damage of the coating, either mechanical of chemical, or loss of bond between coating and substrate will immediately reduce the protective function of the coating. Coatings on reinforced concrete should be able to bridge the (accepted) cracks. This implies that the coating should have a good crack bridging capacity or a crack filling or crack healing properties.
A large running project on self healing materials in The Netherlands (start 2006) has revealed that coatings in particular form a class of materials where self healing properties are desired For concrete structures, in which deterioration of the concrete cover and of the reinforcing steel constitute the most frequent cause of premature failure, the application of a self healing coating can substantially improve the durability and service life of the concrete, meanwhile reducing the maintenance costs.
Crucial for the performance of a self healing coating are:
1. The properties of the coating: Development towards a self healing coating
2. Interlace coating-substrate: type and quality of the bond and self repairing capacity
3. Substrate (concrete): Required properties versus available properties, and this for a wide variety of concrete, including the wide variety of the concrete due to different curing regimes.
Research steps
The research project consists of twenty modules, to be executed partly in parallel and partly in series.
I. Coatings
1. Establishing an inventory of currently used coatings on concrete and of the causes of premature failure of them.
- Properties and failure modes of coatings
- Properties and failure modes of the interface coating-concrete
2. Study of self healing concepts for coatings
- Inventory of good examples of self healing coatings in other industries
- Preconditions for self healing
- Contacts with supplying industries
- Cost aspects (materials, application, long term savings)
3. Design of self healing coatings
- Boundary conditions
- Theory of self healing
- Modelling of self healing processes in coating
4. Experimental testing of self healing coatings
- Mechanical testing (healing of mechanically induced cracks/flaws)
- Testing of bond properties
- Crack bridging properties
- Crack filling properties
The experimental testing includes:
- Macroscopic observations (permeability a.o.)
- Microscopic observations (ESEM, petrographic studies)
5. Modelling for self healing phenomena of the coating
II. Interface coating - concrete substrate
6. Type of bond and bond failures between coating and concrete (see also module 1)
- Chemical bond
- Physical bond
7. Preferable type of bond in view of self healing phenomena
8. Requirements for substrate (including criteria for curing and finishing of concrete sur-faces)
9. Testing and analysis of interface performance under different exposure conditions
- Mechanical testing (bending, fatigue)
- Thermal and hygral cycles
- Freeze-thaw
10. Modelling of interface perlonnance
III. Concrete substrate
11. Characterisation of substrate
- Microstructure / pore structure
- Chemical properties
12. Influencing factors
- Type of cement or binder
- Water/binder ratio
- Curing
13. Transport properties in concrete substrate
- Effect moisture transport in concrete on bond properties (improvement or damaging effect)
- Effect or contribution of moisture transport in concrete on self healing capacity of the coating
14.Testing of concrete substrate
15. Criteria of optimal substrate
IV. Macroscopic, full scale testing and analysis
16. Full scale testing
- Outdoor test wall
- Testing of most promising coatings
- Different exposure conditions: Day-night cycles, seasonal cycles
17. Testing of bond properties (short term and long term perlormance)
- Visual inspection
- Microscopic studies (ESEM, MIP)
- Crack bridging capacity
- Crack filling capacity
18. Execution aspects
- Variability of substrate in real structures
19. Economics
- Material costs and application
- Saved maintenance costs
- hnpact on the building cycle
- Savings denoted to service life extension
- Environmental savings (reduction CO2emission)
20. Establishing guidelines for self healing coatings
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