Since the Great East Japan Earthquake, many concrete seawalls for reconstruction and tsunami prevention are being built. Concrete having high resistance of chloride attack has been demanded for such coastal structures. To reduce future maintenance cost, concrete structures must be highly durable to environmental effects in addition to the chloride attack resistance. The authors have developed a pozzolanic admixture with excellent resistance to chloride attack as well as excellent general durability. The admixture is a mineral fine powder with a BET specific surface area of 10 m2/g of higher. The pozzolanic material (general mixture of 20-40 kg/m3) can be used as an alternative binder of Portland cement like fly-ash. The admixture is useable even in precast concrete factories having fewer storage facilities such as extra silos. The study focuses on properties of steam-cured concrete to consider the use of admixture in such precast concrete production. The experimental study examined various properties of the concrete incorporating the admixture, such as the chloride penetration resistance; compressive strength; dry shrinkage; carbonation; sulfate resistance, and freeze-thaw resistance. Pore distribution of the concrete was also investigated to confirm the effect of the powder material. The test result confirms the excellent higher resistance to chloride penetration of the concrete. In addition, the study presents that the durability of the concrete is comparable with or higher than that of conventional concrete without the admixture.
