Separation of clean aggregates from contaminated concrete waste by thermal and mechanical treatment

As part of a fundamental research for the volume reduction of dismantled concrete, an investigation was carried out addressing the separation of the aggregates and the distribution of the radioactivity into the aggregates of contaminated concrete generated from dismantled nuclear facilities. Radioisotope 60Co was artificially used as a model contaminant for non-radioactive crushed heavy weight concrete taken from the Korea Research Reactor 2 (KRR-2) and light weight concrete from the uranium conversion plant (UCP) by thermal and mechanical treatment. The results showed that most of the 60Co nuclide was easily separated from the gravel and aggregate, and concentrated mainly into the porous fine cement paste. By thermal and mechanical separation treatment, the clean aggregate can be recovered up to 80% from radioactively contaminated concrete waste. The final wastes of formed cement paste were produced by thermal and mechanical treatment. Heavy and light cement pastes were vitrified. Volume reductions of the cement pastes were achieved at about 1/3 and 1/2.5, respectively.