Fine-grade artificial lightweight aggregates (ALAs) with particle diameters within 300-600 mum were manufactured by using a fluidized bed of spherical mullite particles. The product aggregates contained uniformly dispersed closed bubbles and showed excellent characteristics of light weight, high strength, and low water absorption, all of which are of ideal properties for lightweight concrete production. By applying mercury intrusion test, tensile strength was estimated from isostatic compressive strength with excellent reliability. High strength during pumping and casting concrete mix is expected for the fine ALAs from fluidized bed process. (C) 2004 Elsevier B.V. All rights reserved.