The manufacture of lightweight aggregates from recycled masonry rubble

• Heterogeneous and fine-grained masonry rubble as feedstock for the production of lightweight aggregates.
• Results of experiments on the conditions for the manufacturing.
• Results of the experiments on the technical and environmental characterization of the material.
• Concrete production in laboratory and technical scale.
• Outlook on technology, energy consumption and further suitable feed materials.

At present, heterogeneous and fine-grained masonry rubble can only be recycled at very low level. To overcome this limitation, the material was employed as feedstock for the production of lightweight aggregates in a thermal process similar to that used in the manufacture of expanded clay and expanded slate. To that end, the fundamental suitability of masonry rubble as a raw material was evaluated. Experiments were carried out which indicated that lightweight granules with defined, adjustable properties similar to those of natural-material-based aggregates could be manufactured from masonry rubble. Structural lightweight concretes produced with these secondary aggregates achieved comparable performance to lightweight concretes produced with conventional expanded clay. Lightweight recycled building material aggregates represent a product that hardly requires any primary resources in its manufacture. In principle, the technique also seems to be well suited for high-quality recycling of other mineral waste materials.