Recovered cement paste for recycling and production of cement in different countries

Using waste concrete as recycled aggregates is a down-cycling practice because cement paste, responsible for 80–90 % emissions and 40–60 % cost in concrete, is not extracted. A better approach is to separate cement paste from aggregates, which can produce better quality recycled aggregates and recovered cement paste (RCP) with high calcium content. This paper compares processing techniques for producing RCP and proposes a new classification currently absent from reports and standards. We evaluate potential RCP applications in cement production, as raw meal for clinker production and for cement replacement after forced carbonation. Further, we evaluate potential of quality-adjusted substitution of RCP for cement production across a panel of countries, with a range of different economic status, to outline optimal practices for cement recycling. Finally, this paper aims to change the perception of concrete waste, showing that when processed efficiently, it can be recycled into cement with minimal loss at each cycle.