Producing lightweight aggregate of controlled density - by preheating coated pellets under controlled atmosphere and temp. prior to expanding (IT 10.9.80)

摘要

A granular lightweight aggregate is made by drying quarry clay, quarry shale, sand, fly ash or mineral waste to a required moisture content (4-5% H2O), mixing (ball milling) the dried material with a material which produces a reducing atmos. (C contg. material, heavy fuel-oil, sulphite waste), pelletising the mixt. and coating the pellets with an anti sticking powder. The coated pellets are then preheated below the softening temp. in an atmos. of controlled oxygen content and then expanded by heating to at least the softening temp. The density of the aggregate is regulated by strictly controlling the time, temp. and oxygen content during preheating. Used for insulating masonry and structural units and for reinforced and prestressed lightweight concrete. Aggregate of controlled size and density is produced.