Studies1

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Diagnosis, Assessment and Maintenance of Concrete Structures

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Corrosion of Reinforcing Steel Bars


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Survey on Corrosion of
Steel Bars in Existing Structures


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Measurement of Anodic
Polarization Curve for Specimens


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Comparison of Smaller
Diameter Core and
Conventional Core


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Compressive Test of
Smaller Diameter Core

ABSTRACT:
Infrastructure supports our daily lives and economic activities, and infrastructure construction has continued at a steady pace since the end of the war, especially during Japan's period of rapid economic growth (1955-1970). Many of the structures built have been in service for many years now, are aging with much of the population, and will require care. Research and education topics in this laboratory include the inspection and maintenance of concrete structures. Recent topics have included (1) creating a diagnosis method in order to precisely predict the condition of structures, (2) using the diagnosis results to determine maintenance and design and (3) conducting repairs to extend the lifetimes of the structures.

DETAILED:
Infrastructure surrounds us, and includes roads, bridges, tunnels, ports, railway facilities and more. Most of these are built primarily of concrete. Concrete is vital to our lives and economic activities, and is unsurprisingly the most widely used construction material in the world.

In Japan, many of these structures were constructed rapidly after the war, especially during the period of rapid economic growth (1955-1970). In the intervening years, they have aged, and they will require care. Our country is spread from north to south, from the seashore to the mountains. Under severe conditions, some structures have deteriorated faster than expected. Further, some deterioration and damage that was not anticipated in the design phase has been reported.

In this laboratory, the purpose of our research and education is to construct concrete structures with reliable performance in carrying loads and in durability, and to extend the lifetime of existing structures. Recent topics have included (1) creating a diagnosis method in order to precisely predict the condition of structures, (2) using the diagnosis results to determine maintenance and design and (3) conducting repairs to extend the lifetimes of the structures.

One of the research topics involving the prediction of a structure's condition comprises investigating the corrosion of the reinforcing steel bars embedded in the structure with non-destructive methods. Conventionally, self-potential and polarization resistance have been measured to study the condition or corrosion of a reinforcing bar. We have tried a new measuring method that obtains an anodic polarization curve. If we can predict when the corrosion will start, the cost of renovation will decrease and the lifetime of concrete structures can be extended.

We also use a diagnosis method that can predict concrete strength easily and precisely. In the conventional method, concrete cores of 100mm diameter and 200mm height have been obtained by drilling. An alternative method is now being developed. This newer method uses smaller cores of approximately 25mm in diameter, which can reduce the damage caused to structures by invasive diagnosis.

Concrete Engineering Laboratory,
Department of Civil Engineering, Faculty of Engineering, Kyushu University
Professor Hidenori Hamada
Associate Professor Yasutaka Sagawa
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