Preparation of porous ceramics by the hydrothermal reaction of blast furnace slag for use in a water-retentive material

Preparation of porous ceramics by the hydrothermal reaction of blast furnace (BF) slag for use in a water-retentive material was demonstrated. The composition of water-cooled BF slag was granulated to a predetermined size. 1g of slag particles was mixed with 0.1-0.3 mL of water or 0.05-0.5M NaOH aqueous solution, and charged in a Teflon crucible, which has a 1 mm hole at its lid. Slag particles sieved to the predetermined size was added with 10mass% of 0.1 M NaOH solution and charged in a Teflon crucible of 20 mm diameter. The slag was hydrothermally treated at 250°C for 16h. All slag particles smaller than 125 μm solidified, and compacts were obtained. Solidification became more difficult by increasing the size of the slag particles, and solidification of slag particles larger than 500μm was strongly affected by the condition of NaOH solution addition. Prepared porous ceramics showed a cooling effect during a water retention test and may be used as water-retentive materials.