Abstract: A method of densifying a porous substrate with a matrix, includes subdividing the pores present in the porous substrate so as to form in the substrate a network of micropores, the subdividing being performed with a filler composition comprising at least one carbon-containing phase or carbide-containing phase that is accessible via the network of micropores; and infiltrating the network of micropores formed by the filler material by reactive chemical vapor infiltration, the infiltration being performed with a reactive gas composition that does not contain carbon and that includes at least one element suitable for reacting with the carbon of the filler composition in order to form a carbide.