Process for producing a constant density lightweight aggregate

Abstract From the Canadian patent

The present invention provides a process for preparing a granular lightweight aggregate, comprising the stages of pre-drying one or more raw materials, adding additives to the raw material, homogenizing the raw material and additives pelletizing the homogenized material in predetermined sizes powdering the grains with a further substance preheating the, grains in a kiln to a temperature substantially less than the softening point of the grains and expanding or burning the grains at least to the softening temperature of the material wherein, during said grain preheating stage the oxygen rate in the atmosphere in which the grains are preheated is strictly controlled, this oxygen rate being …