Lightweight blocks made of coarse AAC‐granules ‐ Recycled again!

The MPA Bremen has been dealing with the development of recycling methods for autoclaved aerated concrete (AAC) rubble for many years. The aim is to enable the highest possible reuse of AAC as a secondary raw material.

In addition to a functional coating for the reduction of methane emissions from landfill bodies, the results so far have been dry premixed mortars for masonry, masonry blocks and lightweight blocks, which contain only AAC rubble of all fractions occurring during processing instead of natural aggregates.

The aim in the development of these recycling methods was always the technical/physical use of the existing characteristic AAC‐structure with continuing to use the gray energies associated with the granules.

The technique of the “Lightweight Blocks made of coarse AAC‐Granules” enables the production of recycling products that are particularly similar to the primary building material AAC. The principle of the “Lightweight Blocks” is based on the fact that coarse AAC granules are filled into a formwork with the desired component geometry and the remaining pore space is filled with an artificially porous matrix using an injection process.

This approach was optimized and extended in a recently completed research project: The particle size range was expanded, the share of AAC Granules was increased and the required use of binder was reduced. In addition, the working hypothesis not only allows the use of granules from the primary building material AAC, but also granules from the recycling product “Lightweight Blocks”. This new approach has been successfully tested for different binder systems. Autoclaved Aerated concrete becomes consequently a real circular building material for two recycling cycles.