The invention pertains to a method for feeding fly ash into an unburnt brick mold. The method involves preparing a mixture of fly ash, cement, and water, with the fly ash constituting 70%-100% by weight, the cement 0%-30%, and the water 2%-27% of the total weight of the fly ash and cement. The fly ash and cement are thoroughly mixed, and water is added to achieve a moisture content of 5%-30%. The mixture is then formed into pellets with a cross-sectional size of 2-50 mm and optionally a length of 2-50 mm, using techniques such as extrusion, roll forming, pellet milling, or pelletizing. Finally, the pellets are fed into an unburnt brick mold using a conventional feeding system of an unburnt brick manufacturing machine.

The present invention relates to a plastic aggregate comprising the steps of: (i) mixing plastic and at least one cementitious binder to form a first composition, wherein the particles of the plastic have a size distribution between 0.1 to 6 mm; (ii) providing a second composition comprising water, (iii) mixing together the first and second compositions to form a plastic aggregate mixture; and (iv) compressing and heating the plastic aggregate mixture to form the plastic aggregate. The present invention further relates to a plastic aggregate pellet and methods of manufacturing a concrete composition comprising a plastic aggregate.