Many of the concrete structures that constructed during Japan's period of high economic growth now require repair. In this regard, technologies to prolong the service life of concrete through appropriate repair and other measures are essential in ensuring the safe use of aged concrete structures, whose numbers are estimated to increase dramatically in the future. Such repair involves a variety of materials and methods, but as the conditions of environments surrounding concrete structures and the mechanisms of deterioration are various, suitable repair technologies for individual cases have not yet been sufficiently established.

The purposes of this study are to systematize repair technologies by examining the standard concepts (e.g., repair mechanisms, performance requirements for repairs, performance evaluation methods) of concrete structure repair technologies based on joint efforts between the Materials Research Team and Concrete and Metalic Materials Research Team and Advanced Materials Research Team, and to achieve prolongation for the lifetime of concrete structures by clarifying the effects of major repair methods (patching repair, surface coating, crack injecting and grouting for repairing and strengthening in concrete structures) and identifying appropriate repair methods depending on work environments and other conditions.

Combined deterioration caused by frost and salt action is seen in many RC bridge wall rails and wheel guards in cold snowy regions, as such structures are exposed to deicing salt, as well as to airborne salt and snowmelt in coastal areas. However, the impact load-bearing capacity of RC bridge wall rails affected by combined deterioration has not yet been clarified, and no methods have been established to support judgment of whether repair/reinforcement is necessary.

The purpose of this study is to contribute to the appropriate maintenance of RC bridge wall rails in cold environments by presenting inspection/diagnosis techniques to determine the necessity of repair/reinforcement for such walls and appropriate repair/reinforcement measures depending on the extent of deterioration. This was based on the verification of mechanical performance in impact loading and other tests on walls subjected to combined deterioration, as well as through field surveys of wall deterioration condition.

Construction quality control and testing are currently conducted on materials and at different stages of construction, in addition to the implementation of as-built, visual and strength tests. However, no quality testing technologies and judgment criteria have yet been established for the quantitative evaluation of durability and other properties of placed concrete itself. Accordingly, there is a need to establish quality testing technologies in order to ensure that materials have certain properties at the time of acceptance testing, and concrete construction standards (e.g., placement, curing methods) also need to be set in accordance with performance-based specifications.

The purpose of this study is to examine construction control concerning workability and construction/curing methods that meet performance-based specifications, and to investigate completion inspection technologies that enable appropriate quality testing of durability and other properties in placed concrete. This is done through laboratory acceleration, exposure, on-site construction and other tests conducted jointly by the Material Research Team and Concrete and Metalic Materials Research Team with various mix proportions and construction conditions.

In cold regions, technologies enabling appropriate evaluation of concrete structure durability against frost damage are required. Current frost deterioration prediction based on verification of durability is conducted on the assumption that only one type of frost damage is at work. However, two or more forms of such damage (e.g., scaling and cracking) actually progress simultaneously in most cases. In order to prolong the service life of concrete structures, it is therefore necessary to develop methods to evaluate their performance in keeping with real environments in which two or more types of frost damage progress simultaneously.

The purpose of this study is to develop a method to evaluate the performance of concrete in conditions where scaling and cracking progress together. To achieve this, investigation is performed to clarify the effects of scaling and cracking on the various properties of concrete in which these types of damage progress simultaneously, and the chloride ions permeability of such concrete is quantitatively evaluated.