Abstract: Effects of grinding time on density , ratio surface area , particle distribution and micrographs of iron tailing powder were discussed , it concluded that iron tailings powder particles was gradually refined , meanwhile the density first decreased and then increased , the specific surface area increased first and then decreased with the extension of grinding time .When the grinding time was 2 h, the specific surface area reached the maximum value of 700 m2/kg particle size (5 ±2) μm particle content is about 40%, less than 5.13 μm diameter of particles accumulate the highest .But excessive grinding will have weak agglomeration .It was suggested by the analysis of mechanical activation effect on the activity of the iron ore tailing and IR that, at 10%-50%content of the grinding of 2 h iron ore tailings, the flexural strength ratio and the activity index of 3 d, 7 d and 28 d were the maximum.The grinding time maximum activated iron ore tailing .The grain refinement disordered substances increased , resulting in enhanced activity by mechanical grinding .

Key words: mechanical activation;iron ore tailing;activity index;IR