LAUSR

Abstract In this work four incineration bottom ashes (IBA) and coal fly ash (CFA) were directly treated in hydrothermal conditions in autoclave. However, not each ash solidified into a solid product. Therefore, it was checked whether the modification of calcium oxide/silica (C/S) molar ratio of the initial mixtures to the value of 0.83 would enhance the properties of such products. The modification improved the compressive strength of the autoclaved ashes as compared to samples with unchanged C/S ratio in the case of each investigated ash (e.g. from 23.5 to 74.9 MPa). The ashes and products were characterized in detail (XRF, XRD, FTIR, Raman). The heavy metals leaching was conducted to assess the toxicity risk. The regulatory limits for the safe application were not exceeded. Heavy metals were almost totally immobilized in the obtained matrices (over 99%). Therefore, presented procedure can be simply applied for the conversion of hazardous incineration bottom ash into non-toxic material, which can be applied as building material.