Building aggregates

The project "Building aggregates" has developed a technology for the production of lightweight recycling aggregates. The advantage: natural raw materials such as clay are needed for traditional light weight aggregates whereas the production of building aggregates requires only construction waste as a raw material. The quality of these so-called expanded aggregates and the application in the production of light mortar and concretes have also been analyzed.

The demolition material is pre-crushed, milled and homogenized and shaped in a pelleting mixer, followed by thermal treatment in a rotary kiln which stabilizes the expanded aggregates. Experimental analyses have shown that the lightweight aggregates are at least as good as aggregates made from natural raw materials. Some lightweight concretes made from expanded aggregates have better properties than those made from traditional expanded clay. The high quality recycled product can for example be used in lightweight concrete blocks or as lightweight construction concrete.

A huge advantage of the expanded aggregates made from demolition waste is that they are produced almost completely without primary raw materials. Only the expansion agent silicon carbide and a release agent may have to be added.  The joint project also specified that the amount of demolition waste is sufficient to supply the raw material for lightweight concrete production: Every year five to ten million tons of demolition waste are available, the current production figures for lightweight concrete are 6.5 million cubic meters. Therefore lightweight concrete can entirely be produced without using natural raw materials.

The aim of the project to increase resource efficiency in the construction industry can therefore be achieved as the proportion of recycled building materials in concrete production can be increased by building aggregates. Due to the more effective use of material building aggregates are also cheaper than traditional lightweight clay-based concretes. In addition, new markets for the recycling industry and export opportunities for plant engineering will be opening up.