Abstract: The bulk density， particle size distribution， chemical erosion， cylindrical compressive strength and morphology of air-quenched BFS(blast furnace slag)are measured by experiments.The results show that the bulk density increases first and then decreases with the increase of particle size and is the largest in the particle size range of 0.30~1.0mm.The size of slag beads is mainly between 0.30~1.0mm where the bead yield is high. The slag beads do not resist acid erosion. In terms of erosion resistance， larger slag beads are better than smaller ones in the same erosion solution.The smaller the particle size， the greater the cylinder compressive strength of the slag beads and the stronger the ability to bear pressure. The surface of slag beads is smooth and spherical， and the particle size is uniform.The content of amorphous phase of the slag beads is high because of the rapid cooling rate of the slag beads by gas quenching. When the slag beads sizes are less than 0.30mm， the XRD curve becomes the shape of a teamed bread， showing that crystal phase is hardly precipitated and the minerals are amorphous.

Key words: gas quenching, blast furnace slag, bulk density, cylindrical compressive strength, particle size distribution