Porous abrasive articles with agglomerated abrasives and method for making the agglomerated abrasives

A method of agglomerating abrasive grain, comprising the steps:

• a) feeding abrasive grain and a binding material, selected from the group consisting essentially of vitrified bond materials, vitrified materials, ceramic materials, inorganic binders, organic binders, water, solvent and combinations thereof, into a rotary calcination kiln at a controlled feed rate;
• b) rotating the kiln at a controlled speed;
• c) heating the mixture at a heating rate determined by the feed rate and the speed of the kiln to temperatures from about 145 to 1,300° C.,
• d) tumbling the grain and the binding material in the kiln until the binding material adheres to the grain and a plurality of the grains adhere together to create a plurality of sintered agglomerates;
• and
• e) recovering the sintered agglomerates from the kiln, whereby the sintered agglomerates have a three-dimensional shape, a loose packing density of ≦1.6 g/cc and comprise a plurality of abrasive grains.