Sand-lime bricks are masonry blocks formed from quicklime and silicate raw materials and autoclaved in an atmosphere of tensioned steam. During this process, calcium silicate hydrates (CSH phases) are formed, which give this building material the required strength. Compared to the setting reactions that take place very slowly in air, autoclaving leads to an enormous acceleration of CSH phase formation. Although autoclaving is the most energy- and time-intensive variable in the sand-lime brick manufacturing process, it involves many degrees of freedom in execution.

The hardness curves of the autoclaving of sand-lime bricks can be variably adjusted according to the product-specific requirements. However, a fundamental optimization of this process step has not yet been carried out, since previous research projects have mainly dealt with the optimization of sand-lime brick properties as a function of composition. In the project applied for, the multifactorial interrelationships of sand-lime brick production are to be investigated by means of statistical experimental design with the aim of optimizing the autoclaving process in order to reduce production costs. The product quality should at least remain the same or even be increased. The approach using statistical design of experiments is now used successfully as standard in many industries, in particular in the automotive and mechanical engineering sectors.

In the past, the technical parameters influencing the autoclaving of sand-lime brick products were studied exclusively from various individual aspects. However, it has already become clear that the relationships between raw material properties, autoclaving parameters, brick quality (àtarget compressive strength) and the energy required for autoclaving are very complex and depend on numerous overlapping influencing variables and their interactions. Due to the complexity of the interrelationships, it has not been possible to date to reliably calculate production engineering measures for reducing energy consumption. This inevitably means that autoclaving is not used in an optimized manner in operational production practice, even in modern KS plants. The curing process is currently still carried out empirically and has not yet been adequately investigated with regard to KS quality, production costs and energy consumption as well as the environment. This is where the research project comes in.

In order to clarify the understanding of these complex relationships and to determine effective approaches for reducing energy consumption and optimizing quality, methods of statistical experimental design are to be used.Optimized hardening parameters (reaction temperature, pressure, duration, course of the hardening process) are to significantly reduce energy consumption and production costs while maintaining or improving the stone quality. The life cycle assessment is improved and energy tax requirements can be met more easily.