PURPOSE: To provide the title additive which comprises specific fine particles of arom. compds. obtd. froth coal without thermally decomposing it, is used as a mixture with other specific materials, and gives a solid material exhibiting excellent infrared absorption and heat insulation effects.

CONSTITUTION: The title additive comprises fine particles of arom. compds. having particle size of 5μm or lower and is obtd. from coal without thermally decomposing it, e.g. by extracting high-molecular compds. from coal with a solvent such as pyridine and evaporating the solvent. The additive is used as a mixture with a powdered or particulate building material, pref. cement, or with a powdered or particulate building interior material, pref. a wall sand, plaster, or a powdered artificial wall material. The figure shows the change in thermal characteristics of a hardened cement mixture under exposure to near-infrared rays.