| Budget Amount *help |
¥13,700,000 (Direct Cost: ¥13,700,000)
Fiscal Year 1996: ¥5,100,000 (Direct Cost: ¥5,100,000)
Fiscal Year 1995: ¥8,600,000 (Direct Cost: ¥8,600,000)
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| Research Abstract |
Water-retaining concrete structure is used in city water, sewage, agriculture and others. In the mechanics, the durability of this kind of structure is specified by seismic behavior and cracking. On the other hand, the chemical causes which limit the life of this structure are considered to be alkali aggregate reaction, chloride corrosion, carbonation and microbial corrosion. Several ions present in water and concrete itself result in these corrosion. Their preventive measures are cutting off ions and removing ions intruded into concrete.
The results due to grant-in-aid for Scientific Reseasrch are as follows :
(1) Microbially induced corrosion mainly occurs in sewage treatment facilities. The corrosion mechanism becomes clear as sulfuric acid attack and complex carbonation. The main causes are intrusion of SO_4^<2-> and HCO_3^- ions. There are some indexes to determine the damaged depth at repair.
(2) Anion Cl^- causes chloride corrosion. Cations Na^+ and K^+ lead to alkali aggregate reaction. It is clear that mending material should have the function to absorb those ions.
In general, repair about water-retaining concrete structure is composed of removing corroded concrete, mending lacked portion and lining. The methods to determine damaged depth and to mend corroded section are important research theme in this field. But it is impossible for corroded section to be completely removed because of cost. Therefore, the development of mending material is very important for keeping the stability of concrete after repaired. It is also necessary to study the mending material as a whole in order to make the lining yield well. In the future works, there can not be a significant repair unless the mending material and the lining are used jointly, because many water-retaining structures are in the soil.
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