Development of an Alkali-Activated Binder for the Extrusion Process (2023-12)¶

One of the main focuses of current research in the construction industry is the investigation and development of sustainable production methods and building materials. New production methods such as the extrusion of textile-reinforced concrete have great potential, as they can be used to produce lightweight and load path-compliant components. However, concretes with a high binder content and CO2 footprint are currently often used. Alkali-activated materials (AAM) represent a sustainable alternative to conventional concretes. However, the chemical composition, reactivity and rheological behavior usually differ greatly from cement-based systems, which means that there is a great need for research. As part of this work, an innovative AAM was synthesized using basalt and granulated blast furnace slag. For a more precise characterization of the AAM, the solidification time and the heat development were investigated with an isothermal heat flow calorimeter for different binder compositions. Its suitability as a binder for extrusion was also systematically tested. In order to ensure faultless extrusion, the fresh concrete must be conveyable in the extruder and have a high green strength, so that a dimensionally accurate, defect-free and formwork-free production of the components is guaranteed. For the rheological description of the newly developed AAM for the extrusion process, an innovative ball penetration test was used to predict the extrudability. The results show that the AAMs can be reliably developed for the extrusion process and their suitability can be predicted before the actual process. In addition, it was shown that AAMs made from industrial by-products are suitable for this process and that CO2 emissions can be minimized as a result.