Bridges constructed in the high-growth era of the 1970s have already served for more than 40 years since their opening in Japan. The deterioration of bridges caused by fatigue from issues such as increases in the number and load of vehicles, salt damage by airborne chloride ions, and the spraying of anti-freezing agents has become a major problem. Damage to concrete deck slabs is particularly serious. One of the main causes of this damage is fatigue, and the damage is exacerbated when the concrete slabs are in contact with water. In such cases, the surface of concrete deck slabs can be crushed and ground into sand and fine particles. Freezing and thawing actions with salt accelerate this phenomenon.

The requirements for concrete used in replacement members are as follows: 1) fatigue deterioration of concrete accelerated by salty water should not occur easily, 2) the creep and shrinkage degrees are small enough, 3) concrete should protect reinforcing steel from corrosion. Concrete that meets all the above requirements can be produced by using Blast furnace slag sand instead of conventional fine aggregate materials. In this study, the precast member with high durability is developing with Blast furnace slag sand which is by product of Iron manufacture.

* Blast Furnace slag Sand