Austrian Mineral Waste Streams for Alkali-Activation: A Comprehensive Suitability Evaluation Approach

Alkali activated materials (AAMs) are an interesting class of alternative construction materials with potentially low environmental impact and physicochemical properties fulfilling the requirements for a wide range of engineering applications. One reason therefore is their ability to utilize mineral wastes and industrial by-products as raw materials to produce clinker-free binders. To date the research is mostly focused on fly-ash, GGBS and metakaolin-based AAMs, whereas the utilization of other probable viable wastes and by-products for AAM production (e.g. metallurgic slags, mineral wools, and construction and demolition waste) are often overlooked. Such wastes and by-products are produced in substantial amounts and frequently deposited in landfills, posing a notable environmental burden. In this work, the systematic evaluation of various Austrian mineral wastes and by-products to be utilized as AAM precursors is presented. First, the physical, chemical and, mineralogical characteristics of wastes were assessed. Thereafter, their potential reactivity as binder components was systematically investigated in AAM paste mixes series. The developed binder systems were investigated by characterizing fresh and hardened pastes through visual observations, spread flow, and compressive strength. Moreover, a fundamental understanding of the environmental material characteristics was attained by leaching tests. This strategy enabled a preliminary reactivity evaluation of different mineral wastes and the development of binder systems, exhibiting high waste content, suitable fresh properties and high strength development, for further tuning and optimization.