Revolutionizing sustainable transport infrastructure with low-carbon alkali-activated materials: solid waste valorization, diverse applications, and future challenges

Green ecology and energy conservation face growing challenges as lagging indicators in urban development and renewal. Cement concrete, the primary material carrier of urban civilization, imposes severe environmental pressures due to high carbon emissions from production. Concurrently, mounting solid waste generated from resource extraction and urban regeneration has overwhelmed conventional landfilling approaches, falling short of public demands for green, safe, and sustainable alternatives. Against this backdrop, alkali-activated materials (AAMs) have emerged as a promising substitute for cement-based composites, offering substantial potential for solid waste valorization, reduced carbon footprint, and competitive engineering properties. Transport infrastructure, a major consumer of construction materials, exhibits broad compatibility with varied material specifications, positioning it as an ideal platform for large-scale application of AAMs. However, current research on AAM remains predominantly focused on fundamental characteristics (e.g., mechanical performance, durability, and microstructure), leaving their systematic deployment in transport infrastructures critically underexplored, with no comprehensive review yet available to systematize this emerging domain. Therefore, this paper presents an overview on the composition, reaction mechanisms, and properties of AAMs, with a focus on their multifaceted applications in transport infrastructure (including pavements, road base, soil subgrade, precast components, and heavy metal immobilization), as well as the economic and environmental benefits. Meanwhile, the current technical challenges and future perspectives toward revolutionizing transport infrastructure with low-carbon AAMs are also discussed, providing strategic insights and practical guidance for sustainable transport infrastructure engineering.