Hiroki Maenami

Hydrothermal solidification of inorganic waste materials

To create an environmently friendly community, the authors have investigated the recycling technology of inorganic, wastes to make high performance building materials and the stabilization technology of toxic heavy metals by using hydrothermal treatment. The inorganic waste materials used were bottom ash and fly ash from incinerated municipal waste, incinerated ash from sewage sludge, concrete waste, and construction sludge. These waste were mixed with Ca(OH)/sub 2/ and autoclaved for 6 h at 180/spl deg/C under saturated steam pressure. Except for the specimen by using incinerated ash from sewage sludge, the formation of tobermorite (Ca/sub 5/(Si/sub 6/O/sub 18/H/sub 2/)/spl middot/4H/sub 2/O) and hydrogarnet (Ca/sub 3/Al/sub 2/(SiO/sub 4/)(OH)/sub 8/) were observed. The flexural strength of the specimens varied from 3.2 to 16.2 MPa with the bulk density of 1200 to 1550 kg/m/sup 3/. The higher SiO/sub 2/ content and the finer particle size gave the higher strength. The amount of dissolved heavy metal (Pb) was decreased to 1/40 after autoclaving, suggesting the possibility of the heavy metal fixation by hydrothermal treatment. In addition, hydrothermally solidified specimens using incinerated ash from sewage sludge and construction sludge had 1.5 times of higher self humidity controlling property than the ordinal wood.

Recycle of inorganic wastes by hydrothermal technology

In order to build up a sustainable society, the authors have investigated the recycling technology of inorganic wastes with low energy consumption. Sewage sludge ash, concrete waste, and construction sludge were used as raw materials. These waste were mixed with Ca(OH) ₂ and formed by uniaxial pressing. The specimens were autoclaved for 6 h at 180degC under saturated steam pressure. The flexural strength of the specimens varied from 3.2 to 9.4 MPa with the bulk density of 1200 to 1550 kg/m³. The strength development was caused by filling of the initial void among the particles with tobermorite (Ca₅(Si₆O₁₈H₂)middot4H ₂O) and hydrogarnet (Ca₃Al₂(SiO₄)(OH)₈) formed by hydrothermal treatment. To apply these solidified inorganic waste to paving tile, determined that Ca(OH) ₂/wastes mass ratio is 15/85 for plant production condition. The paving tile had comparable performance with brick, block and concrete pavement