Sustainable autoclaved aerated concrete produced from cementless binders

The United Kingdom’s net zero strategy aims to reduce carbon emissions to lead the world to a greener and more sustainable environment. Using waste materials as an alternative to Portland cement in concrete production will contribute to achieving this strategy, as cement production causes approximately 8% of global CO2 emissions. Moreover, the effective utilisation of these waste materials in concrete applications could reduce the environmental issues and costs associated with their disposal in landfills. Autoclaved aerated concrete (AAC) is a lightweight concrete characterised by possessing better insulation behaviour and higher heat resistance than conventional concrete. The aim of this research is to produce eco-friendly autoclaved aerated concrete based on by-product waste materials. The possibility of using Incinerated Sewage Sludge Ash (ISSA) as a precursor in geopolymer concrete was investigated. Furthermore, Cement Bypass Flue Dust (CBFD) as an activator of alkali-activated materials and as a binder to produce AAC was evaluated. ISSA did not achieve the expected results, as the investigation proved it to be an inert material. On the contrary, CBFD gave promising results, so it was incorporated into the AAC production. The results showed that using CBFD resulted in compressive strength up to 6.7 MPa for a density of 704 kg/m₃.