Research Progress and Review on the Curing/stabilization of Municipal Sludge Using Alkali-activated Geopolymer Binding Materials

With the rapid increase in municipal sludge production, solidification/stabilization (S/S) has become one of the most widely used and effective technologies for sludge treatment. However, traditional cement-based solidification often suffers from low strength, poor water stability, and high risks of heavy metal re-leaching, highlighting the urgent need for efficient and low-carbon alternative binders. Alkali-activated geopolymer binders have demonstrated superior solidification performance. This paper reviews the mechanical properties and solidification mechanisms of municipal sludge stabilized with geopolymer materials in both domestic and international studies. The strength development, water stability, solidification mechanisms, leaching toxicity, and sustainability characteristics of geopolymer-solidified sludge are systematically summarized. Furthermore, the effects of alkali activator type, precursor composition, and dosage on the unconfined compressive strength of solidified sludge are analyzed. Current research gaps in understanding the solidification/stabilization performance and mechanisms of alkali-activated geopolymers are discussed, and targeted research recommendations are proposed. This review provides new insights and perspectives for the scientific study and practical application of alkali-activated geopolymer binders, offering theoretical support and engineering guidance for the low-carbon solidification/stabilization of municipal sludge.