The invention relates to a process for producing proppants, including the following steps: providing red mud, providing fly ash, producing a mixture from the red mud and the fly ash so that the mixture has a first moisture content in the range of 7 to 30 wt. %, producing a granular product from the mixture, and sintering the granular product.

A ceramic for construction or technical applications, composed of at least one of Municipal Solid Waste Incinerator Bottom Ash (MSWIBA) and other recycled industrial solid waste and different methods of forming such ceramics. Various techniques illustrate how ceramics are formed using at least one of extrusion shaping, dry powder compaction and agglomeration, any of which can be preceded by a pre-treatment process of received feedstock.

A lightweight high-strength ceramsite, comprising solid raw materials and activator as the raw materials, which can be respectively expressed in parts by weight, the solid raw materials: 100 parts, the activator: 1-15 parts; wherein said solid raw materials comprise fly ash: 100 parts, high-alumina fly ash, bauxite and red mud: 6-18 parts, silica fume: 1-5 parts, surfactant: 0.1-3 parts, plasticizer: 6-24 parts; and said activator comprises alkali metal hydroxide: 5-20 parts and alkali metal silicate: 80-95 parts. The lightweight high-strength ceramsite product prepared has a density level of 700-1100 kg/m3 and cylindrical compressive strength of 10-20 MPa, and thus is not susceptible to damage.

Described herein are sintered spheres, obtained from red mud, comprising at least aluminium oxide, iron oxides, silicon oxide, and titanium oxide, characterized in that the roundness and the sphericity of the sintered spheres is higher than 0.6.

Described is further a process for the production of sintered spheres, comprising the following steps: a) providing red mud, being a residue from alumina production, b) optionally adjusting the pH value of the red mud to a value lower than 9, c) granulating the red mud from step b) under continuous drying, d) sintering the granulate from step c).

Described herein is also the use of sintered spheres as proppant in fracking processes or as aggregate or lightweight fine aggregate (LWFA) for construction purposes or for geological solidification processes.