Recycling belite cement clinker from post-demolition autoclaved aerated concrete - assessing a new process

Increasing post-demolition autoclaved aerated concrete (pd-AAC) waste is mainly landfilled due to its physical properties and lacking recycling processes. A promising technology is the production of recycled belite cement clinker, which can partially substitute Portland cement clinker. This paper presents experimental data of recycled belite cement clinker production from pd-AAC that has been successfully demonstrated on technology readiness level 4-5 and its associated lifecycle assessment. Different supply chains for pd-AAC and energy are examined. The closed-loop pd-AAC recycling via the belite route that aims for Portland cement clinker substitution shows significant potential savings in environmental impacts. These savings could reach 0.77 kg CO2-Eq/kg pd-AAC compared to the status quo (landfilling) by using renewable electricity, and 0.34 kg CO2-Eq/kg pd-AAC by using natural gas. The gained reduction of around 13.5 % is significant considering that it is the result of substituting only 15.5 % of the overall input material.