Sand-lime bricks are manufactured from the natural raw materials lime, sand and water, mechanically compacted and hydrothermally hardened. Almost 98 % of the total production volume (approx. 8 million t in 2018) consists of blocks (h = 248 mm) and KS-XL formats (h ≥ 498 mm). Around 20% of the KS-XL products are cut for the production of prefabricated KS construction kits with installation plans, with a total of around 30,000 t of sawing sludge being generated per year in the approx. 80 sand-lime brick plants nationwide, for which there is currently no use.

The KS sawing sludge is produced during the manufacture of hydrothermally hardened KS plan elements and contains mainly CSH phases and finely ground silicate components that have been mechanically broken down by the sawing process and are said to have reaction-promoting properties. In the future, these sawing slurries are to be used in sand-lime brick production as an optimization additive.

Since the effect of the sawing slurries on the production process and the brick properties are not known, their use is to be tested in the laboratory/technical center and then evaluated in operational production practice. Because sawing slurries from sand-lime brick material act, on the one hand, as fillers and, on the other, as crystallization nuclei due to their content of calcium silicate hydrates (CSH), their use is expected to have the potential both to improve product quality and to conserve resources (reduction of the lime dose and the intensity of hydrothermal hardening as well as environmentally relevant emissions).