The granulometric and mechanical properties of a poly(vinyl acetate) (the matrix) and calcium carbonate (the filler) composite system were investigated. This particulate system was prepared either by blending unground or ground particles of the two materials, or by co-grinding the two products in a laboratory dry agitated bead mill. The follow-up of the evolution of the particle size, illustrated by scanning electron microscope (SEM) photos, has permitted the identification of the mechanism by which the composite is formed by co-grinding. This composite is constituted by filler particles of less than 1mum homogeneously dispersed in the poly(vinyl acetate) matrix. The characterization of the mechanical properties of blends has shown that the storage tensile modulus is enhanced when adding more than 20 weight percent filler. As for the co-ground composite, this filler produces a great reinforced effect, especially at a temperature higher than the glass transition temperature of the synthetic matrix.