The European Union is transitioning from a linear to a circular economy under the European Green Deal, emphasizing efficient raw material use and promoting alternatives to virgin materials. The concept of anthropogenic construction products, introduced in earthworks by SIST EN 16907-2:2019, underscores the need for detailed knowledge of recycled material characteristics to ensure the efficient and sustainable use of industrial residues in green construction. Ashes from incineration processes vary in phase composition, (latent) hydraulic activity, amorphous content, and physical properties, all of which influence their potential as binder materials in civil engineering. This study analysed eight types of ashes, focusing on phase composition and time-dependent hydration processes. Calcium aluminate hydrates were identified as the primary crystalline hydration products in all ashes, and reactivity results correlated with the behaviour of ash pastes. All ashes exhibited at least partial hydration activity. These findings emphasize the importance of systematically analysing key parameters that define ash reactivity and suitability for construction applications.