Iron Supply Capacity of Porous Concrete Using Steelmaking Slag Aggregate for Seaweed Beds or Fish Reef Blocks

Abstract

The desertification of coastal regions is a worldwide problem. It is believed that one of the potential influences is a reduction in the concentration of dissolved iron in seawater. On the other hand, there is a high demand for the use of steelmaking slag generated from iron works. Steelmaking slag concrete, hereafter referred to as SSC, is made from the byproducts of steelmaking, such as steelmaking and ground granulated blast-furnace slags. It has been shown that although SSC releases iron, the dissolved iron is oxidized and precipitates promptly. In the present research, porous-type SSC (POSSC) using hot-metal pretreatment slag (HPS) as an aggregate was manufactured, with the purpose of increasing the amount of iron released from HPS. In addition, the influence of incorporating humus into the paste on the concentration of dissolved iron in artificial seawater and the compressive strength of POSSC was investigated. Two commercially available leaf mulches were used as the humus. The effects of the void ratio and the water-to-binder ratio of the paste were also examined. As a result, it was confirmed that the larger the measured void ratio of the POSSC, the higher the concentration of total iron released by the POSSC. It was also demonstrated that, although a humus fraction of 2% of the volume of the HPS caused an approximately 2 N/mm2 reduction in the compressive strength, the humus clearly stabilized the long-term presence of dissolved iron in the artificial seawater.