Methods

A method of manufacturing a carbonated plastic aggregate comprising; mixing plastic particles and at least one cementitious binder comprising at least one metal oxide or metal silicate to form a first composition; mixing the first composition with a second composition comprising water to form a pre-mixture; agglomerating the pre-mixture to form a plastic aggregate; and carbonating the at least one metal oxide or metal silicate by an active carbonation process. The active carbonation process may comprise exposing the plastic aggregate to CO2 enriched gas, which may be industrial flue gas or obtained by direct air capture. The binder may comprise Ground-Granulated Blast Furnace Slag (GGBS), fly ash, and/or Portland cement, and the plastic may be derived from plastic-based foam, and preferably comprises polyurethane or polyisocyanurate. A method of carbonating a plastic aggregate pellet is also defined, comprising; providing a plastic aggregate pellet comprising a plastic particle, at least one cementitious binder comprising at least one metal oxide or at least one metal silicate, and water; and carbonating the at least one metal oxide or at least one metal silicate by active carbonation. A concrete composition comprising a carbonated plastic aggregate obtained by either of the methods is also specified.