Abstract: By using as the lightweight aggregate, in the manufacture of lightweight concrete, polystyrene-bead materials of particularly controlled characteristics in regard to bead size and coefficient of variation of absolute volume, there is obtained a substantial improvement in regard to the accuracy with which the density of the product lightweight concrete can be controlled or preordained. Since the strength and insulation-value properties are closely related to the density, the improvement aids in the design and production of more economical parts.