Process of making a blistered, crystallizable glass material

A process of making a blistered crystallizable glass material with simultaneous utilization of mineral-containing waste products, comprising the steps of:

• supplying as raw materials a mixture of materials originating from domestic or industrial waste products with calcareous and optionally other glass-forming minerals to the upper end of a rotary kiln,
• keeping said rotary kiln at a temperature sufficient to melt the raw materials supplied during their passage therethrough to form a molten bath flowing downwards through the lower part of said rotary kiln,
• injecting fly ash from the lower end of said rotary kiln above said molten bath over the burning zone of said rotary kiln thereby to burn residual carbon in the fly ash and to at least partially incorporate the remainder in said molten bath with the proviso that the raw materials are supplied to the upper end of the rotary kiln and the fly ash is injected from the lower end in such amounts that the finished glass material made therefrom will show a content of about 20-30% by weight CaO and not more than about 5% by weight Al.sub.2 O.sub.3
• and causing the molten material thus formed to flow off from the lower end of said rotary kiln and subsequently cooling said material thereby to form a blistered crystallizable material.