Let us use as an example a fungus that extracts heavy metals. When using sucrose as a carbon source at a 30 C ambient temperature the fungus produces gluconic and citric acids, plus surfactants and emulsifiers that enhance the leaching efficiency. The metals stay in solution and can be recovered either electrolytically or by ion exchange. This is wonderful if we view the fly ash as a difficult waste from coal burning thermo-generating stations. At this point we do not even have an educated guess about what the same aspergillus niger might be able to do to fresh or hardened concrete.
Various studies have some scary findings.
Washington University School of Medicine in St. Louis researchers surveyed buildings flooded during the summer of 1993. Even buildings that had been gutted, decontaminated with bleach and rebuilt had over 7,700 spores pcm. In contrast, mold counts in control buildings were less than 750 spores pcm. The mold problem begins with the boarding up flood-damaged buildings after an evacuation, which creates perfect conditions for mold growth. And once mold is established, its near-microscopic, reproductive spores permeate the building, making complete decontamination practically difficult.