Agglomerate abrasive grain comprising incorporated hollow microspheres

An agglomerate abrasive grain comprising a plurality of individual abrasive grains incorporated into a binding matrix, wherein:

• the abrasive grains are selected from the group consisting of corundum, fused corundum, sintered corundum, alumina zirconia, silicon carbide, boron carbide, cubic boron nitride, diamond, and mixtures thereof;
• the binding matrix is obtained from a mixture of an aluminosilicate, an alkali sodium silicate, and water;
• the aluminosilicate and the alkali sodium silicate having a molar ratio of Al2O3 to SiO2 ranging from 1:2 to 1:20;
• the binding matrix is hardened at temperatures below 500° C.;
• the agglomerate abrasive grain has an open porosity ranging from 5% by volume to 25% by volume,
• the agglomerate abrasive grain further comprising hollow bodies that are incorporated into the binding matrix and that provide the agglomerate abrasive grain with a closed porosity, wherein
• the hollow bodies are 5% to 40% by volume of the agglomerate abrasive grain, and
• the sum of closed and open porosity is less than 50% by volume of the agglomerate abrasive grain;
• further wherein the abrasive grains and the hollow bodies have an average particle diameter ranging from 5 μm to 250 μm, and wherein the ratio of the average particle diameter of the abrasive grains to the average particle diameter of the hollow bodies ranges from 2:1 to 1:2.