There is increasing concern about concrete deterioration (such as peeling and disintegration) resulting from reinforcing bar corrosion in railway concrete structures such as viaducts. Development of an effective and economical repair method correspond to the degree of deterioration is demanded.
The repair method using corrosion inhibiting material is generally used for concrete structures affected by salt damage. The Railway Technical Research Institute (RTRI) has already developed a salt absorbent and two types of corrosion inhibiting material utilizing a salt absorbent (i.e. corrosion inhibiting paste and corrosion inhibiting mortar). A repair method using these (SSI method: Fig. 1a) has been put to practical use.
Another more economical repair method has now been developed.
Concrete poured with insufficiently desalinized sea sand generally contains about 2 kg/m3 of chloride ions. To examine an economical repair method for this type of concrete, a corrosion test and a trial construction at actual concrete structure level were performed for a case where only rust-preventive paste was used (Fig. 1b). The measurement of corrected half-cell-potential demonstrated that a reinforcing bar with a content of chloride ions up to 3 kg/m3 was determined corrosion-free if the corrosion inhibiting paste was applied at least halfway around the reinforcing bar (Fig. 2). Since this method does not use corrosion inhibiting mortar, the costs can be reduced by about 20% compared to the conventional SSI method.