Method for producing a track superstructure which underwent partial foaming

A method for making a track bed structure for a railway on a subgrade inclined transversely to the length thereof, wherein

• an elastic drain mat (14) is arranged on the subgrade,
• a ballast body (16) of individual ballast stones (18) having voids between them is formed, notably on the drains mat (14), if existing,
• sleepers (20) are embedded into the ballast body (16),
• rails (24) are fastened on the sleepers (20), and
• for positional fixation of the ballast stones (18) arranged substantially only within load transfer regions (26) of the ballast body (16) below the sleepers (20), a foamable material (28) is introduced into the voids between the ballast stones.

A method for preparing mineral fractions connected to each other by a foamed polymer material, wherein, in said method,

• polymer-fixed mineral fractions are introduced into a furnace,
• the polymer-fixed mineral fractions are heated in such a manner that the polymer material is converted into the gaseous phase,
• the gas is subjected to an exhaust-gas cleanup process, and
• the mineral fractions substantially freed of polymer are removed from the furnace.