On the use of blast furnace slag and steel slag in the preparation of green artificial reef concrete

This study is motivated by the need for the development of green artificial reef concrete (GARC) and the reuse of granulated blast furnace slag (GBFS) and steel slag (SS) from the steel manufacturers located near coastline. GARC was developed with industrial waste including GBFS, SS and flue gas desulfurization gypsum as the major raw materials. Physical properties and compressive strength development of the prepared GARC were examined. Hydration products of GARC paste were investigated through X-ray diffraction, differential scanning calorimetry and scanning electron microscope techniques. The developed GARC shows a 28-day compressive strength of 71.4 MPa and a density of 2765.5 kg/m3, which contains industrial waste accounting for 98% by weight of its total solid raw materials. Investigation of hydration products in GARC paste reveals that the major hydration products are ettringite and C-S-H gel with a very dense microstructure, without considerable amount of portlandite that is commonly found in traditional concrete. The absence of portlandite is favorable for lowering the pH valve of artificial reefs, which would be benefit for avoiding the accumulation of fouling organisms like barnacles on the surface of concrete artificial reefs. An experimental-scale deployment of GARC specimens in the sea preliminarily demonstrates that GARC is suitable for the attachment growth of algae. The successful development of GARC mainly composed of GBFS and SS could potentially offer great benefits in promoting the sustainable development of steel manufacturers closely located to coastline as well as fishery industry.