On the Prediction of Strength and Optimum Mix-Designs of Mineral-Waste-Based Alkali-Activated Materials

Reducing the carbon footprint of building material production (~9% of anthropogenic CO₂) in the short term is essential to achieve global climate targets. In this regard, certain mineral wastes and secondary raw-materials show large potential as low-CO₂ alternatives to be utilized in alkali-activated materials (AAMs). In order to establish mineral-waste-based AAMs as strong future competitors in the construction industry, functional binder systems have to be developed to meet material requirements. Tapping into these unexploited waste streams and exploring their potential as binder components is based on their respective mineralogical and chemical compositions, which determine the desired material properties of the mix-design (expressed e.g. in elemental ratios such as Si/Al). By generating waste-stream-related patterns and variable associations in the context of bulk chemistry and mineralogy of available waste types, factors for the binder development stage are elaborated. During this step, optimum experimental conditions can be achieved by statistical methods such as the design of experiments (DOE) and response surface methodology (RSM), including desirability function-based methods. Such approaches yield time- and/or cost-efficient strategies by optimising the amount of available resources used. For preliminary results the following interactive variables were considered: (i) waste content, (ii) compressive strength and (iii) water/binder ratio. Future focus is given on the evaluation of more complex systems containing a variety waste sources.