Geochemical interaction in the system: Acid dump sediment, water and the building material 'lignite fly ash'

摘要

We investigate lignite fly ash monolithically injected into unsaturated acid dump sediments. For this aim lab-scale experiments were performed with (1) rain water and (2) acid mine water. (1) If fly ash was irrigated by rain water a dense structure of ettringites will be formed inside the whole ash body. Secondary calcite's formed close to the sediment-ash interface indicate the lowering of pH and CO_2 influence from the soil air. A micro-crack system could be identified inside the hydrated ash body. (2) In difference to the contact with rain water the interaction with acid mine water causes the formation of different mineralization zones inside the ash body. The inner zone is partially formed by ettringites and CSH-phases followed by Gypsum and metal hydroxides towards to the ash-sediment interface. Especially the rim mineralization zone shows low hydraulic permeability. Therefore, we found inside the fly-ash body an unaltered ash zone.