Industrial waste recycling approach: An ecofriendly geopolymer binder for clean and sustainable environments (A 24-h green recycling process)

Abstract

Bypass cement waste dust (BCWD) significantly threatens human health and the environment due to its high concentrations of fine, respirable crystalline silica, chlorine, and sulfates. This study introduces an eco-friendly recycling approach that processes BCWD at a low temperature of 80 °C for 24 h. The method combines 50% BCWD with an equal proportion of natural black volcanic ash (BVA) and varying concentrations of NaOH to produce an innovative material known as Green Geopolymer Bypass Binder (GGBB). Notably, some GGBB mixtures achieved compressive strengths of 35 MPa within 24 h, with a slight increase to 35.55 MPa after 7 days. Further characterization revealed that the mixture with the highest compressive strength also exhibited a 23.29% mass loss of hydrated phases, as confirmed through TG/DTG analysis. Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) analyses verified the formation of geopolymer phases, including calcium aluminum silicate hydrate (C-A-S-H or Al-Tobermorite) and calcium sodium-potassium aluminum silicate hydrate (C-N-K-A-S-H or Philipsite). These phases play a crucial role in enhancing the material's properties and significantly contribute to its superior strength. This recycling process stands out as a “green” innovation, requiring low-temperature compared to traditional high-temperature methods. The resulting GGBB material offers a sustainable pathway to repurpose hazardous waste into practical applications such as eco-friendly bricks, paving stones, and prefabricated wall panels. By advancing cleaner and greener construction practices, GGBB underscores a commitment to environmental sustainability and resource efficiency.