General Research During the Previous Period(1.Apr.2006-31.Mar.2011)
1. A Study on the Effects of Anti-Freezing Agents on Steel Bridge Coatings

The results of previous studies performed by the Material Research Team (formerly known as the Materials Research Division) revealed that bridges in mountainous and urban areas, which are not classified as corrosive environments affected by salt damage, are also subjected to corrosion caused by the application of chloride-based anti-freezing agents for winter road surface management. It is known from these studies that salt tends to concentrate in sections that come into contact with anti-freezing agents and related snowmelt, as opposed to the general salt supply seen in environments such as coastal areas. It is therefore necessary to investigate recoating methods for steel bridges in consideration of these environmental conditions.
The purpose of this study was to develop a rational method for recoating steel bridges in environments where chloride-based anti-freezing agents are used.

2DA Study on the Effects of Anti-Freezing Agents on Weathering Steel

The environmental conditions outlined above are also common to bridges for which weathering steel is used. It is therefore necessary to examine efficient technologies to form protective rust layer as well as methods for partial coating and other forms of maintenance/management for weathering steel materials in consideration of these environments.
The purpose of this study was to investigate and develop such approaches for weathering steel materials in places where chloride-based anti-freezing agents are used.

3DA Study on the Use of Recycled Aggregate Concrete in Cold Snowy Regions

Increased use of recycled aggregate containing concrete from demolished structures is required in order to support the formation of a recycling-oriented society. Against this background, the Material Research Team (formerly known as the Materials Research Division) drafted quality standards regarding recycled coarse aggregate for application to plain concrete in cold snowy regions. While it is necessary to expand the scope of recycled aggregate application to reinforced concrete structures in order to further increase its usage, there is a risk that aggregate recycled from concrete structures affected by anti-freezing agents may be used in cold snowy regions. When using such aggregate, it is necessary to consider how its salt content influences the corrosion of reinforcement and freeze-thaw resistance.
The purposes of this study were to clarify how salt contained in recycled concrete aggregate affects corrosion in concrete reinforcements, and to provide information for the establishment of quality standards concerning salt content in recycled aggregate. A simple on-site salt content measurement method for recycled aggregate was also proposed, along with criteria to enable judgment of whether such aggregate can be used.

4DA Study on Porous Concrete Application in Cold Snowy

Porous concrete is different from normal concrete in that it has continuous pores. It is used as ecological concrete, as its pores provide the functions of drainage and sound absorption as well as enabling vegetation growth. However, since the material also has low strength and low freeze-thaw resistance, the Materials Research Team (formerly known as the Materials Research Division) examined its applicability to cold snowy regions.
The purpose of this study was to establish mix proportions, structures and applications for porous concrete suited to cold regions by examining technologies designed to enable the utilization of highly strong, durable and functional porous concrete for noise insulation walls and other roadside facilities, RC bridge wall rail and other road structures, and drainage pavement in heavily trafficked sections. The results are expected to contribute to automobile noise reduction and other roadside environment improvements based on utilization in cold snowy regions.


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