Disclosed are a method for preparing a non-sintered shell-wrapped ceramsite using solid waste meanwhile immobilizing a heavy metal in river sediment, and a non-sintered river-sediment-based shell-wrapped ceramsite, which relate to the technical field of building materials. The disclosure combines river sediment with a solid waste powder and an alkali activating powder material, and adopts multiple-step granulations to realize particle size control and physical pore formation, thereby obtaining a non-sintered ceramsite. A sulfoaluminate cement and a Portland cement are used to encapsulate the non-sintered ceramsite and form a shell by wrapping, thereby preparing a non-sintered river-sediment-based shell-wrapped ceramsite with internal porosity and dense shell.

Disclosed are a method for preparing a non-sintered shell-wrapped ceramsite using solid waste meanwhile immobilizing a heavy metal in river sediment, and a non-sintered river-sediment-based shell-wrapped ceramsite, which relate to the technical field of building materials. The disclosure combines river sediment with a solid waste powder and an alkali activating powder material, and adopts multiple-step granulations to realize particle size control and physical pore formation, thereby obtaining a non-sintered ceramsite. A sulfoaluminate cement and a Portland cement are used to encapsulate the non-sintered ceramsite and form a shell by wrapping, thereby preparing a non-sintered river-sediment-based shell-wrapped ceramsite with internal porosity and dense shell.

A method for simultaneously drying and carbonating a mineral waste material that includes carbonatable calcium and/or magnesium compounds and/or silicate, aluminate or silicate-aluminate phases in a spray dryer, wherein a starting material slurry is provided including the mineral waste material in the form of particles with a D90500 m and at least 30 wt.-% water, a hot gas is provided including at least 4 Vol.-% CO.sub.2 and fed into the spray dryer, the starting material slurry is sprayed into the hot gas in the spray dryer wherein a temperature of 100 C. and a relative humidity of <50% are adjusted in the spray dryer, the starting material slurry is transformed into evaporated water and a dry, carbonated product comprising calcium carbonate and/or one of silica gel or alumina gel or silica-alumina gel, and the dry, carbonated product is separated from the gas and evaporated water.

A method for preparing lightweight clay-based aggregates, the aggregates being suitable for use notably in civil engineering works, in particular road uses, and construction. The method for preparing lightweight aggregates includes at least the following steps: a) a step of granulating a clay-based mixture, so as to obtain aggregates, b) a step of drying the aggregates obtained, so as to obtain dried aggregates, c) a step of heat treatment of the dried aggregates, this step having two successive substeps: i) a first substep of heat treatment carried out under a reducing atmosphere at a temperature Ti of between 900 C. and 1200 C. approximately, ii) a second substep of heat treatment carried out under an oxidizing atmosphere at a temperature T2 of between 1050 C. and 1300 C. approximately, and d) a step of cooling the aggregates.

A method for preparing lightweight clay-based aggregates, the aggregates being suitable for use notably in civil engineering works, in particular road uses, and construction. The method for preparing lightweight aggregates includes at least the following steps: a) a step of granulating a clay-based mixture, so as to obtain aggregates, b) a step of drying the aggregates obtained, so as to obtain dried aggregates, c) a step of heat treatment of the dried aggregates, this step having two successive substeps: i) a first substep of heat treatment carried out under a reducing atmosphere at a temperature Ti of between 900 C. and 1200 C. approximately, ii) a second substep of heat treatment carried out under an oxidizing atmosphere at a temperature T2 of between 1050 C. and 1300 C. approximately, and d) a step of cooling the aggregates.