New types of binders as alternatives to cement – Where are we heading?

Low-clinker composite cements and cements containing recycled construction materials in accordance with the DIN EN 197-5 and -6 standards, but also other types of cement that were granted national technical or project-specific approvals, have increasingly been used in recent years. Such advancements in cement technology generally aim to further reduce the proportion of carbon-intensive clinker and thus contribute to mitigating greenhouse gas emissions. In addition, in-depth research is being conducted into clinker-free binders designed to replace cement entirely. Besides the conventional “hydraulic approach,” this research has given rise to a wide array of alternative binders that, despite exhibiting different mechanisms of action, produce concrete with the same strength and durability characteristics as known from standard cement. Against this backdrop, they are also of fundamental interest for producing structural concrete. These include alkali-activated binders or geopolymers made from industrial by-products or natural pozzolans, hydraulic calcium hydrosilicates, binders based on magnesium silicate or carbonate, and thermally and/or mechanically processed recycled concrete, which is subjected to additional carbonation in some cases and can exhibit considerable reactivity. This allows for a wide range of combinations and variations in achievable properties, making concrete produced with such binders a prime example of a performance-based concept. This concept focuses on the performance of the concrete using appropriate test and evaluation methods to provide solutions customizable to specific use cases. This presentation summarizes the current state of development and standardization of some alternative binders, outlining where the “binder journey” might take us.